COURSE: Medical Parasiology, (MBChB, 3rd YEAR) – 2010- Lecture

SUBJECT: Medical Mycology

FACULTY: Dr Mohamed Abdille, PhD

HOUR 1
TEACHING OBJECTIVE: To impart sufficient basic science of the medically important fungi to
assist you in diagnosing mycotic diseases and to impart adequate clinical knowledge to raise
your index of suspicion for mycotic diseases.

I. INTRODUCTION

MYCOLOGY: Mycology is the study of fungi and their multiple functions in nature.
A. CLASSIFICATION
Fungi are eukaryotic organisms that do not contain chlorophyll, but have cell walls,
filamentous structures, and produce spores. These organisms grow as saprophytes and
decompose dead organic matter. There are between 100,000 to 200,000 species depending
on how they are classified. About 300 species are presently known to be pathogenic for
man. There are five kingdoms of living things. The fungi are in a kingdom of their own: the
Kingdom Fungi.
TAXONOMY

Prokaryocyte

Eukaryocyte
Eukaryocyte *

Eukaryocyte

Eukaryocyte *

KINGDOM CHARACTERISTIC EXAMPLE

Monera Bacteria
Actinomyces
Protista Protozoa

Fungi Fungi

Plants Plants
Moss
Animals Arthropods
Mammals
Man

* This common characteristic is responsible for the therapeutic dilemma in anti-mycotic

 therapy.
The taxonomy of the Kingdom Fungi is evolving and is controversial. Formerly based on gross and light
microscopic morphology, studies of ultra structure, biochemistry and molecular biology provide new
evidence which is being used to form taxonomic positions. Medical Mycology
MEDICAL MYCOLOGY
There are four types of mycotic diseases:
1. Hypersensitivity - an allergic reaction to molds and spores. Indoor air pollution 2.
Mycotoxicoses - poisoning of man and animals by feeds and food products contaminated by
fungi which produce toxins from the grain substrate.
3. Mycetismus- the ingestion of pre-formed toxin (mushroom poisoning).
4. Infection
These lectures are concerned only with the last type: pathogenic fungi which cause infections.
Most common pathogenic fungi do not produce toxins.
B. MORPHOLOGY
Pathogenic fungi can exist in the yeast or mycelial form. Yeasts are unicellular organisms, which
reproduce by budding, and hyphae are multicellular filamentous structures, constituted by
tubular cells with cell walls. A mass of hyphae (mycelium) is called mycelia. The mycelial forms
branch; the pattern of branching and the width of the mycelium are aids to the morphological
identification. If the mycelia do not have SEPTA, they are called coenocytic (non-septate). The
terms "hypha", "mycelium" and “mold” are frequently used interchangeable. Some fungi may
occur in both the yeast and mycelial forms. These are called dimorphic fungi.
Dimorphic fungi
The dimorphic fungi have two forms:
1. YEAST - (parasitic or pathogenic form). This is the form usually seen in tissue sections, in
some exudates, or if cultured in an incubator at 37ºC.
2. MYCELIUM - (saprophytic or mold form). The form observed in nature or when cultured at
25ºC. Conversion to the yeast form appears to be essential for pathogenicity in the
dimorphic fungi.
Spores
Fungi are identified by several morphological or biochemical characteristics, including the
appearance of their fruiting bodies. The asexual spores may be large (macroconidia,
chlamydospores) or small (microconidia, blastospores, arthroconidia). Dimorphic fungi are
confirmed by converting to the alternate form and some dimorphic fungi can be confirmed by
molecular methods.
C. EPIDEMIOLOGY
Fungi are ubiquitous in nature and human beings are constantly exposed to them. Most mycotic
agents are soil saprophytes and mycotic diseases are generally not communicable from
person-to-person (occasional exceptions: Candida and some dermatophytes). Outbreaks of
fungal disease may occur, but these are due to a common environmental exposure, not
communicability.
The establishment of a mycotic infection usually depends on the size of the inoculum and on
the resistance of the host. The severity of the disease seems to depend mostly on the
immunologic status of the host. Thus, the demonstration of fungi, for example, in blood drawn
from an intravenous catheter can correspond to colonization of the catheter, to transient
fungemia (i.e., transitory dissemination of fungi through the blood stream without disease), or to
a true infection. The physician must decide which is the clinical status of the patient based on
clinical parameters, general status of the patient, laboratory results, etc. The decision is not
trivial, since treatment of systemic fungal infections requires the aggressive use of drugs with
various degrees of toxicity.
GEOGRAPHICAL DISTRIBUTION
Most of the fungi, which cause systemic infections, have a peculiar, characteristic ecologic niche
in nature. This habitat is specific for several fungi which will be discussed later. In this
environment, the normally saprophytic organisms proliferate and develop. This habitat is also
the source of fungal elements and/or spores, where man and animals, incidental hosts, are
exposed to the infectious particles. It is important to be aware of these associations to diagnose
mycotic diseases. The physician must be able to elicit a complete history from the patient
including occupation, avocation and travel history. This information is frequently required to
raise, or confirm, your differential diagnosis.
D. DIAGNOSIS
1. Wet Mount: Skin scrapings suspected to contain dermatophytes or pus from a lesion can be
mounted in KOH on a slide and examined directly under the microscope. 2. Dermal
Hypersensitivity: Skin Testing used to be popular as a diagnostic tool, but this use is now
discouraged because the skin test may interfere with serological studies, by causing false
positive results. It may still be used to evaluate the patient's immune status, as well as a
population exposure index in epidemiological studies.
3. Serology: This tool may be helpful when it is applied to a specific fungal disease; there are
no screening antigens for “fungi” in general. Because fungi are poor antigens, the efficacy of
serology varies with different fungal agents. The significant serologic tests will be discussed
under each mycosis.
The most common serological tests for fungi detect antibodies and are based on latex
agglutination, immunodiffusion, complement fixation and enzyme immunoassays. While
latex agglutination may favor the detection of IgM antibodies, double immunodiffusion and
complement fixation usually detect IgG antibodies. Some EIA tests are being developed to
detect both IgG and IgM antibodies.
There has been some progress in developing serologic tests, which can detect specific
fungal antigens, e.g. cryptococcosis, histoplasmosis and aspergillosis.
4. Direct fluorescent microscopy: may be used for identification of fungi, even on non-viable
cultures or on fixed tissue sections. The reagents for this test are presently difficult to obtain. 5.
Biopsy and histopathology: A biopsy may be very useful as a source of the tissue-invading
fungi and for the identification of the organism. Usually the Gomori methenamine silver (GMS)
stain is used to reveal the organisms which stain black against a green background. The H&E
stain does not always tint the organism, but it will demonstrate the inflammatory cells. Can be
applied to alveolar lavage and other body fluids.
6. Culture: A definitive diagnosis requires a culture and identification. Pathogenic fungi are
usually grown on Sabouraud dextrose agar (SDA). It has a slightly acidic pH (~5.6);
cyclohexamide, penicillin, streptomycin or other inhibitory antibiotics are often added to
prevent bacterial contamination and overgrowth. Each specimen is inoculated on duplicate
sets of media and incubated separately at 25ºC and 37ºC to reveal dimorphism. The
cultures are examined macroscopically and microscopically. The cultures are not considered
negative for growth until after 4 weeks of incubation.
7. DNA probes: Ribosomal DNA is hybridized to a labeled DNA probe. This test is rapid (1
Hour) and species specific. It is not available for many organisms and it is expensive.

E. TREATMENT
Mammalian cells do not contain the enzymes which will degrade the cell wall
polysaccharides of fungi. Therefore, these pathogens are difficult to eradicate by the animal
host defense mechanisms. Because mammals and fungi are both eukaryotic, the cellular
milieu is biochemically similar in both. The cell membranes of all eukaryotic cells contain
sterols; ergosterol in the fungal cell membrane and cholesterol in the mammalian cell
membrane. Thus, most substances which may impair the invading fungus will usually have
serious side effects on the host. Although one of the first chemotherapeutic agents (oral
iodides) was an anti-mycotic used in 1903, the further development of such agents has been
slower than the development of anti-bacterial agents. The selective toxicity necessary to
inhibit the invading organism with minimal damage to the host has been difficult to establish
within eukaryotic cells.
 The primary antifungal agents follow:
1. Polyene Derivatives:
Amphotericin B, a polyene antimycotic, has been the drug of choice for most systemic
fungal infections. It has a greater affinity for ergosterol in the cell membranes of fungi than
for the cholesterol in the host's cells; once bound to ergosterol it causes disruption of the cell
membrane and death of the fungal cell. Amphotericin B is usually administered intravenously
(patient usually needs to be hospitalized), often for 2-3 months. The drug is rather toxic;
thrombo-phlebitis, nephrotoxicity, fever, chills and anemia frequently occur during
administration. Although newer drugs have been shown to be as efficacious and less toxic,
amphotericin B is still the gold standard for comparison as well as the therapy of last resort
for severe infections.
Lipid based amphotericin: As effective, less toxic, more expensive.
Nystatin. Very limited use, primarily for candida infections. There is now an IV lipid
formulation under clinical trials.
2. Azoles The azoles (imidazoles and triazoles), including ketoconazole, fluconazole,
itraconozole, voriconazole and posaconazole are being used for muco-cutaneous
candidiasis, dermatophytosis, and for some systemic fungal infections. Fluconazole is
presently essential for the maintenance of AIDS patients with cryptococcosis because it will
penetrate the spinal fluid. The general mechanism of action of the azoles is the inhibition of
ergosterol synthesis which affects cell wall synthesis. Oral administration and reduced
toxicity are distinct advantages.
Ketoconazole, Fluconazole, Itraconazole, Voriconazole, Posaconazole.
3. Griseofulvin. Griseofulvin is a very slow-acting drug which is used for severe skin and
nail infections. Its effect depends on its accumulation in the stratum corneum where it is
incorporated into the tissue and forms a barrier, which stops further fungal penetration and
growth. It is administered orally.
4. 5-fluorocytosine
5-fluorocytosine (5-FC) inhibits RNA synthesis and has found its main application in
cryptococcosis (to be discussed later). It is administered p.o.
5. Allylamines
Terbinafine (Lamisil). For dermatophyte infections
6. Echinocandins (caspofungin)

A new antifungal agent recently approved by the FDA

F. CLINICAL CLASSIFICATION OF THE MYCOSES
a. Superficial mycoses
b. Subcutaneous mycoses and
c. Systemic mycoses
d, Opportunistic mycoses
The Superficial mycoses (or cutaneous mycoses) are fungal diseases that are confined to the
outer layers of the skin, nail, or hair, (keratinized layers) rarely invading the deeper tissue or
viscera. The fungi involved are called dermatophytes.
The Subcutaneous mycoses are confined to the subcutaneous tissue and only rarely spread
systemically. They usually form deep, ulcerated skin lesions or fungating masses, most
commonly involving the lower extremities. The causative organisms are soil saprophytes, which
are introduced through trauma to the feet or legs.
The Systemic mycoses may involve deep viscera and become widely disseminated. Each
fungus type has its own predilection for various organs which will be described as we discuss
the individual diseases.
The opportunistic mycoses are caused by ubiquitous saprophytes and occasional pathogens
that invade the tissues of those patients who have:
1) Predisposing disease (diabetes, cancer, leukemia, etc.) or
2) Predisposing conditions (agammaglobulinemia, steroid or antibiotic therapy).
II. ACTINOMYCETES
We will discuss three genera of actinomycetes: Actinomyces, Nocardia, and Streptomyces.
These organisms have been shown to be higher bacteria, but they were thought to be fungi for
many years because they have filamentous forms, 0.5 to 0.8 microns in diameter, which appear
to branch. Some species form aerial mycelia in culture. The clinical manifestations of infection
are similar to those of a systemic fungal infection. It is now clear that they are not fungi but are
closely related to the mycobacteria. Some facts that you must know about these genera are that
Actinomyces are anaerobic, while Nocardia and Streptomyces are aerobic. Nocardia stain
partially acid-fast, Actinomyces and Streptomyces are not acid-fast. Actinomyces produce
granules. Most actinomycetes in tissue do not stain with the H & E stain commonly used for
general histopathology. All genera may produce granules; Actinomyces almost always produces
granules.
A. ACTINOMYCOSIS
Actinomycosis is a chronic suppurative and granulomatous disease of the cervico-facial,
thoracic or abdominal areas
The most common cause of actinomycosis is the organism Actinomyces israelii which infects
both man and animals. In cattle, the disease is called "lumpy jaw" because of the huge abscess
formed in the angle of the jaw. In man, A. israelii is an endogenous organism that can be
isolated from the mouths of healthy people. Frequently, the infected patient has a tooth abscess
or a tooth extraction and the endogenous organism becomes established in the traumatized
tissue and causes a suppurative infection. These abscesses are not confined to the jaw and
may also be found in the thoracic area and abdomen. The patient usually presents with a pus
draining lesion, so the pus will be the clinical material you send to the laboratory.
This organism, which occurs worldwide, can be seen histologically as "sulfur granules"
surrounded by polymorphonuclear cells (PMN) forming the purulent tissue reaction. The
organism is a gram-positive rod that frequently branches. The laboratory must specifically be
instructed to culture for this anaerobic organism.
These lesions must be surgically drained prior to antibiotic therapy and the drug of choice is
large doses of penicillin (18-20 million units q day).
B. NOCARDIOSIS
Nocardiosis primarily presents as a pulmonary disease or brain abscess in the U.S. In Latin
America, it is more frequently seen as the cause of a subcutaneous infection, with or without
draining abscesses. Brain abscesses are frequent secondary lesions. The most common
species of Nocardia which cause disease in human beings are N. brasiliensis and N. asteroides.
These are soil organismswhich can also be found endogenously in the sputum of apparently
healthy people. N. asteroides is usually the etiologic agent of pulmonary nocardiosis while N.
brasiliensis is frequently the cause of sub-cutaneous lesions. The geographic distribution of
these organisms is worldwide.
The material sent to the laboratory, depending on the presentation of the disease, is sputum,
pus, or biopsy material. These organisms rarely form granules. The Nocardia are aerobic, gram
positive rods and stain partially acid-fast (i.e., the acid-fast staining is not uniform). There are no
serological tests, and the drug of choice is Bactrim (Trimethoprim plus sulfamethoxazole). The
nocardia grow readily on most bacteriologic and M. tuberculosis media. C. STREPTOMYCOSIS
The streptomyces species usually cause the disease entity known as mycetoma (fungus
tumor). These infections are usually subcutaneous, but they can penetrate deeper and invade
the bone. Some species produce a protease which inhibits macrophages. Material sent to the
laboratory may be pus or skin biopsy. The streptomycetes are aerobic like Nocardia, and can
grow on both bacterial and fungal (Sabouraud) media. They produce a chalky aerial mycelium
with much branching. It is important to let the laboratory know the organism you suspect
because most bacterial pathogens will grow out overnight, but the actinomycetes take longer to
be visible on the culture plates (48-72 hours). The various species of streptomyces produce
granules of different size, texture and color. These granules along with colonial growth and
 biochemical tests allow the bacteriologist or mycologist to identify each species. The organisms
are found world-wide. There are no serological tests, and the drugs of choice are the
combination of sulfamethoxazole/trimethoprim or amphotericin B. Surgical debridement is often
indicated. In the tropics this disease may go undiagnosed or untreated for so long that surgical
amputation may be the only effective treatment.
HOUR 2
III. YEASTS
Yeasts are single-celled budding organisms. They do not produce mycelia. The colonies are
usually visible on the plates in 24-48 hours. Their soft, moist colonies resemble bacterial
cultures. There are many species of yeasts, which can be pathogenic for humans. We will
discuss only the two most significant species: Candida albicans and Cryptococcus neoformans

A. CANDIDIASIS (Candida albicans)

There are several species of the genus Candida that cause disease. They are divided into two
broad categories; albicans and non-albicans species. The infections caused by all species of
Candida are called candidiasis. Although this discussion is limited to Candida albicans it is
important in clinical practice to speciate Candida because drug resistance and treatment varies
with species.
Candida albicans is an endogenous organism. It can be found in 40-80% of normal human
beings. It is present in the mouth, gut, and vagina. It may be present as a commensal or a
pathogenic organism. The establishment of infection with Candida species appears to be a
property of the host - not the organism. The more debilitated the host, the more invasive the
disease. Infections with Candida usually occur when a patient has some alteration in cellular
immunity, normal flora or normal physiology. Patients with decreased cellular immunity have
decreased resistance to fungal infections. Prolonged antibiotic or steroid therapy destroys the
balance of normal flora in the intestine allowing the endogenous Candida to overcome the host.
Invasive procedures, such as cardiac surgery and indwelling catheters, produce alterations in
host physiology and some of these patients develop Candida infections. Although it most
frequently infects the skin and mucosae, Candida can cause pneumonia, septicemia,
endocarditis, esophagitis, etc. in the compromised patient.
The organism occurs worldwide.
The clinical material to be sent to the laboratory depends on the presentation of the disease:
blood cultures, vaginal discharge, urine, feces, nail clippings or material from cutaneous or
mucocutaneous lesions. Candida is a polymorphic yeast, i.e., yeast cells and pseudohyphae are
produced. It has been shown that Candida needs a transcription repressor to maintain the yeast
form. This ability to assume various forms may be related to the pathogenicity of this organism.
The yeast form is 10-12 microns in diameter, gram positive, and it grows in 2 or 3 days on most
bacterial and fungal media. Pseudohyphae may be formed from budding yeast cells that remain
attached to each other. Spores (chlamydospores) may be formed on the pseudomycelium which
can be used to identify different species of Candida. Candida albicans (specifically) also
produces germ tubes which serve as a key to speciation. Some mycologists think that the
pseudomycelia represent a more invasive form of the organism. The species are identified by
biochemical reactions and morphology.
Detection: Beta-glucan assay. This test has been used for only a few years. The drug of choice
for vaginitis and cutaneous infections is nystatin (topical) and those for systemic infections are
itraconazole and fluconazole. If an artificial heart valve or in-dwelling catheter becomes infected,
it must be replaced. Drug therapy alone will not suppress the organism if the foreign body
remains in the host. This resistance is due to biofilm production which we will discuss in the last
hour.
Candida species (other than albicans) account for an increasing number of nosocomial
infections
B. CRYPTOCOCCOSIS (Cryptococcus neoformans)
Cryptococcosis manifests itself most commonly as meningitis but in recent years pulmonary
infections have been recognized.
Infection may be subacute or chronic. The highly fatal meningoencephalitis caused by C.
neoformans has a prolonged clinical evolution of several months. The patients symptoms may
begin with vision problems, lethargy and headache, which then progress to delirium, nuchal
rigidity leading to coma and death; unless the physician is thinking about cryptococcus and does
a spinal tap for diagnosis and institutes aggressive anti-mycotic therapy. The CSF is examined
for its characteristic chemistry (elevated opening pressure, elevated protein and decreased
glucose), cells (usually monocytes), and evidence of the organism. The latter is measured by
the visual demonstration of the organism (India Ink preparation) or by a serologic assay for the
antigen of C. neoformans. Death usually occurs due to cerebral edema and increased
intracranial pressure.
C. neoformans is a very distinctive yeast. The cells, which are spherical, and 5-10 microns in
diameter, produce buds that characteristically are narrow-based and a polysaccharide capsule
surrounds the organism. There is evidence that the capsule may suppress T-cell function and
can be considered a virulence factor. C. neoformans also produces an enzyme called
phenoloxidase (melanin) which appears to be another virulence factor.
The geographical distribution of this organism is world-wide.
The ecological niche of C. neoformans is pigeon and chicken droppings. However, although this
organism can be easily recovered from pigeon droppings, a direct epidemiological link has yet to
be established between exposure to pigeon droppings and a specific human infection. Infection
and disease production is probably a property of the host--not the organism. This organism is
ubiquitous, especially in areas like abandoned buildings contaminated with pigeon droppings.
The portal of entry is the respiratory system. Evidence is developing which indicates that the
initial exposure may be many years prior to the manifestation of disease. The organism can be
sequestered for this time.
The India ink test, which demonstrates the capsule of this yeast, is supplemented by the latex
agglutination test for antigen, which is more sensitive and more specific. The latex agglutination
test measures antigen, NOT antibody. A decreasing titer indicates a good prognosis, while an
increasing titer has a poor prognosis.
When you consider Cryptococcosis, think of Capsules and CNS disease. In addition to causing
meningitis, C. neoformans may occasionally infect lungs and skin. The disease in the lungs and
skin is characterized by the formation of a granulomatous reaction with giant cells. As with other
fungal diseases, there has been an increase in the recognition of pulmonary infection. The yeast
may also form a mass in the mediastinum called a cryptococcoma.
The clinical material sent to the laboratory is CSF, biopsy material, and urine (for some
unexplained reason the organism can be isolated from the urine in both the CNS and systemic
infections). This organism will grow overnight on bacterial or fungal media at 37 C. but growth is
a little slower at room temperature. In culture the organism grows as creamy, white, mucoid
(because of the capsule) colonies. Growth in culture is usually visible in 24-48 hours. As the
culture ages, it turns brown due to a melanin produced by the phenoloxidase. The organism is a
round, single cell, yeast surrounded by a capsule. Species identification is based on
physiological reactions. Pathologists use a mucicarmine stain, which tints the capsule, to identify
the organism in tissue sections. Usually there is little or no inflammatory response. In chronic
cryptococcosis the tissue reaction is granulomatous.
The Direct Fluorescent Antibody test identifies the organism in culture or tissue section
specifically, by causing the yeast cell wall to fluoresce green. To test the patient's serum there
are 3 serologic tests: The Indirect Fluorescent Antibody test, the Tube Agglutination test for
antibody, and the Latex Agglutination test for antigen. The latex agglutination test can be used
as a prognostic test. As the patient improves, the serum and CSF antigen titer will decrease.
The drugs of choice to treat cryptococcus infection are amphotericin B plus 5-flucytosine (5-FC)
or amphotericin plus fluconazole. 5-FC and fluconazole are oral drugs. If either is given as the
only treatment, there are relapses so most physicians use two drugs simultaneously. Actually,
these two drugs are synergistic with amphotericin B and thus, their association is advantageous.
 IV. SUPERFICIAL MYCOSES
The superficial (cutaneous) mycoses are usually confined to the outer layers of skin, hair, and
nails, and do not invade living tissues. These fungi are called dermatophytes. Dermatophytes,
or more properly, keratinophilic fungi, produce extracellular enzymes (keratinases) which are
capable of hydrolyzing keratin.
A. CLINICAL MANIFESTATIONS
Tinea means "ringworm" or "moth-like". Dermatologists use the term to refer to a variety of
lesions of the skin or scalp.
Tinea corporis – small lesions occurring anywhere on the body.
Tinea pedis – "athlete's foot." Infection of toe webs and soles of feet.
Tinea unguium (onychomycosis) – nails. Clipped and used for culture. Infection usually
lifelong.
Tinea capitis – Fungus infection of the hair. Frequently found in children.
Tinea cruris – “jock itch." Infection of the groin, perineum or perianal area.
Tinea barbae – ringworm of the bearded areas of the face and neck.
Tinea versicolor –Characterized by a blotchy discoloration of skin which may itch. Up to 25% of
the general population may have this lesion.. Diagnosis is usually possible by direct microscopic
examination of KOH-treated skin scrapings which show a typical aspect of mycelia and spores
described as "spaghetti and meatballs." Caused by Malassezia furfur,
B. ECOLOGY
The dermatophytes (skin plants) causing human infections may have different natural sources
and modes of transmission:
Anthropophilic – usually associated with humans only; transmission from man to man by close
contact or through contaminated objects.
Zoophilic – usually associated with animals; transmission to man by close contact with animals
(cats, dogs, cows) or with contaminated products.
Geophilic – usually found in the soil, transmitted to man by direct exposure.
Knowledge of the species of dermatophyte and source of infection are important for proper
treatment of the patient and control of the source. Invasion by zoophilic or geophilic organisms
may cause inflammatory disease in man.
Geographic distribution: Dermatophytes occur worldwide, but some species have geographically
limited distribution.
C. ETIOLOGIC AGENTS
There are three genera of dermatophytes:
1. Trichophyton sp. (19 species)

Infect skin, hair and nails. Take 2-3 weeks to grow in culture. The conidia are large
(macroconidia), smooth, thin-wall, septate (0-10 septa), and pencil-shaped; colonies have loose
aerial mycelia, which produce a variety of pigments. Species identification requires special
biochemical and morphological techniques. Trichophyton rubrum is presently the most common
cause of tinea in Blacks in South Carolina. Rarely can cause subcutaneous infections (kerion) in
immunocompromised individuals, particularly patients with chronic myelogenous leukemia.
2. Microsporum sp. (13 species)
May infect skin and hair, rarely nails. Its prevalence has decreased significantly. One species
(M. audouini) when prevalent (20 years ago I South Carolina) could easily be identified on the
scalp because infected hairs fluoresce a bright green color when illuminated with a UV-emitting
Wood's light. The loose, cottony mycelia produce macroconidia which are thick-walled, spindle
shaped, multicellular, and echinulate (spiny). Microsporum canis is one of the most common
dermatophyte species infecting humans and the most commonly found in white children in
South Carolina.
3. Epidermophyton floccosum (Only one species in this genus)
Infect skin and nails and rarely hair. Yellow-colored, cottony cultures; usually readily identified
by the thick, bifurcated hyphae with multiple, smooth, club-shaped macroconidia of 2-4 cells. D.
 THERAPY
Skin infections can be treated (more or less successfully) with a variety of drugs, such as:
Griseofulvin
Tolnaftate (Tinactin) available over the counter - Topical
Clotrimazole Topical
Miconazole Topical. "Step up to the mike."
Ketoconazole Oral seems to be most effective for tinea versicolor and other dermatophytes.
e Oral
(Lamisil) Oral, topical. For skin and nail infections. (Digger Dermatophyte).
For infections involving the scalp and particularly the nails, griseofulvin is commonly used. This
antimycotic must be incorporated into the newly produced keratin layer to form a barrier against
further invasion by the fungus. This is a very slow process requiring oral administration of the
drug for long periods - up to 6-9 months for fingernail infections and 12-18 months for toenail
infections, however it is of low cost and an oral medication.
Itraconazole and terbinafine are now the drugs of choice for onychomycoses – but there is still
about 20% treatment failures. Itraconazole best for tinea versicolor.
E. The Id reaction
Patients infected with a dermatophyte may show a lesion, often on the hands, from which no
fungi can be recovered or demonstrated. It is believed that these lesions, which often occur on
the dominant hand (i.e. right-handed or left-handed) are secondary to immunological
sensitization to a primary (and often unnoticed) infection located somewhere else (e.g. feet).
These secondary lesions will not respond to topical treatment but will resolve if the primary
infection is successfully treated either with topical or systemic drugs.
F. CLINICAL MATERIAL FOR THE LABORATORY
Hair, skin or Nails.
HOUR 3
V. FILAMENTOUS FUNGI
A. CHROMOBLASTOMYCOSIS - A chronic, localized infection of subcutaneous tissues caused by
several species of dematiaceous (black pigmented) fungi. The 3 most common agents are: 1. Fonsecaea
pedrosoi
2. Cladosporium carrionii
3. Phialophora verrucosa
These fungi, recognized by a variety of names, are saprobes located in soil and decaying
vegetation. The route of entry is usually by trauma. The lesions are sub-cutaneous and the
surface can be flat or verrucous and they take several years to develop. These organisms are
called dematiaceous fungi, because they have a black pigment in the mycelium cell wall (in
culture and in tissue). In tissue these fungi form sclerotic bodies which are the reproductive
forms dividing by fission. The sclerotic bodies from all species appear similar. These organisms
induce a granulomatous reaction.
The etiologic agents of chromoblastomycosis are septate, mold-like, branching, darkly pigmented mycelia which
produce asexual fruits called conidia. We identify these fungi in culture by the shape and formation of the conidia
and biochemical tests. The melanin in the pigment may be a virulence factor.
The fungi have a world-wide distribution especially in warmer climates like the tropics or
southern U.S.
The specimens to send to the laboratory are: pus or tissue.
There is still no really successful therapy. It is chronic, fibrotic, and usually with superimposed
bacterial infection. The sclerotic bodies protect the fungus from host defenses. Excision and
local heat have been used with some success. Terbinafine, itraconazole are now being used to
treat (or control) this disease. Posaconazole has recently been shown to be efficacious.
There are no serological tests to aid in the diagnosis.
B. MYCETOMA
Mycetoma (fungus tumors) is also a chronic, subcutaneous infection. These are called
eumycotic mycetoma (tumors caused by the TRUE fungi as opposed to those caused by
actinomycetes). These agents frequently invade contiguous tissue, particularly the bone. A
diagnosis of the etiologic agent is essential for patient management because the prognosis and
therapy differs.
Mycetoma characteristics:
1. tumefaction - swelling
2. granules - a variety of colors (white, brown, yellow, black, etc.).
3. draining sinus tracts
The three most common etiologic agents are:
1. Madurella mycetomatis
2. *Exophiala jeanselmei
3. *Pseudallescheria boydii
*The most common in the US.
Geographic distribution: World-wide and the organisms are associated with the soil, thus
infections of the feet and legs are most common.
Clinical specimens for diagnosis:
1. pus – with granules
2. tissue – for histological examination
The color, size and texture of the granules are an aid in the diagnosis of mycetomas. The agents
of mycetoma are all filamentous fungi, which require 7-10 days for visible growth on the culture
media, and then another several days for specific identification. These fungi are identified by the
colonial morphology, conidia formation and biochemical reactions. The species of fungi cannot
be distinguished in histopathological tissue sections.
There are no serologic tests.
Treatment is very difficult, but excision, terbinafine and itraconazole have been used with some
success. Posaconazole is now giving good results.
C. MUCORMYCOSIS
Mucormycosis is an acute inflammation of soft tissue, usually with fungal invasion of the blood
vessels. This rapidly fatal disease is caused by several different species in this class. The
mucormycetes, like the candida species, are ubiquitous and rarely cause disease in an
immunocompetent host. Some characteristic underlying conditions which cause susceptibility
are: diabetes, severe burns, immunosuppression or intravenous drug use. The portal of entry is
inhalation, ingestion, surface contamination (burns)
The three most common genera causing this clinical entity are:
1. Rhizopus species *
2. Mucor species
3. Absidia species
Characteristics: world-wide distribution, commonly in soil, food, organic debris, seen on
decaying vegetables in the refrigerator and on moldy bread. Rhinocerebral and pulmonary
infections are common. This disease is frequently seen in neutropenic patients and the
uncontrolled diabetic.
Typical case: An uncontrolled diabetic patient comes to ER (may be comatose depending on the
state of diabetes) and a cotton-like growth is observed on the roof of the mouth or in the nose.
These are the hyphae of the organism. If untreated, the patient will die within a few hours or
days. What do you do first to help this patient ? Controlling the diabetic state is most important
while administering amphotericin B.
These fungi have a tendency to invade blood vessels, particularly arteries, (angioinvasive),
adhere to endothelial cells, invade and cause necrosis. They then enter the brain via the blood
vessels and by direct extension through the cribiform plate. This is why they cause death so
quickly.
Culture: A rapid growing, loose, white mold which is visible in 24-48 hours. With age, and the
formation of sporangia, the colony becomes dark gray. The sporangia contain the dark spores.
The mycelium is, wide (15-20 microns), ribbon-like and non-septate (coenocytic). This same
appearance is clear in tissue sections. The species are identified by the morphology in culture.
 Treatment consists of debridement and amphotericin B.
There is an immunodiffusion test available, but the physician cannot wait for these results before
instituting rapid, vigorous intervention. The diagnosis and treatment must be immediate and
based primarily on clinical observations as the mortality can be as high as 50 %. D.
ASPERGILLOSIS
Aspergilli produce a wide variety of diseases. Like the mucormycetes, they are ubiquitous in
nature and play a significant role in the degradation of plant material as in composting. Similar to
candida and the mucormycetes, they rarely infect a normal host.
There are three clinical types of pulmonary aspergillosis:
1. Allergic - hypersensitivity to the organism. Symptoms may vary from mild respiratory
distress to alveolar fibrosis.
2. Fungus ball – which is characteristically seen in the old cavities of tuberculosis
patients. This is easily recognized by x-ray, because the lesion (actually a colony of
mold growing in the cavity) is shaped like a half-moon (crescent). The patients may
cough up the fungus elements because the organism frequently invades the
bronchus. Chains of conidia can sometimes be seen in the sputum.
3. Aggressive tissue invasion. Primarily a pulmonary disease, but the aspergilli may
disseminate to any organ. They may cause endocarditis, osteomyelitis, otomycosis
and cutaneous infections.
Aspergillosis is difficult to diagnose:
1. Clinical symptoms are not specific.
2. Radiography is non-specific (except for fungus ball).
3. Blood cultures seldom positive.
4. Serology seldom positive early enough for intervention.
5. Invasive procedures required for early detection.

There are more than nine hundred species of aspergilli. The most common etiologic agents of
aspergillosis in the United States:
1. Aspergillus fumigatus
2. A. niger
3. A. flavus
The organism is distributed world-wide and is commonly found in soil, food, paint, air vents.
They can even grow in disinfectant.
Culture: Aspergilli require 1-3 weeks for growth. the colony begins as a dense white mycelium
which later assumes a variety of colors, according to species, based on the color of the conidia.
The hyphae are branching and septate. Species differentiation is based on the formation of
spores as well as their color, shape and texture.
Histopathology: The septate hyphae are wide and form dichotomous branching, i.e., a single
hypha divides into two even branches of hyphae, and then the mycelium continues branching in
this fashion.
Serology: There are two serological tests for aspergillosis; the first is an Immunodiffusion test.
There may be 1 to 5 precipitin bands. Three or more bands usually indicate increasingly severity
of the disease. i.e., tissue invasion. The second is an EIA measure of galactomannan –
specificity –99.6 % but only 50 % sensitive.
Treatment: Voriconazole and Amphotericin B.
VI. DIMORPHIC FUNGI
A. BLASTOMYCOSIS (Blastomyces dermatitidis)
Blastomycosis is a chronic granulomatous disease which progresses slowly. Although the
pulmonary and skin involvement is the most common, B. dermatitidis frequently affects bone,
prostate and other organs.
Blastomycosis frequently presents as a cutaneous or a respiratory disease. The cutaneous lesions
may be primary (usually self-limiting) or secondary (a manifestation of systemic disease). The
patient who presents with a complaint of respiratory symptoms will frequently remark about loss
 of appetite, loss of weight, fever, productive cough, hemoptysis and night sweats. These
symptoms resemble those of tuberculosis. The X-ray shows obvious pulmonary disease. To
make the specific diagnosis the physician must be aware of blastomycosis Sputum sent to the
laboratory for "culture" will not
yield the organism. The laboratory must be alerted to look for fungal organisms or to look
specifically for blastomyces. Some patients have a sub-clinical or “flu-like” response to infection.
Laboratory specimens: depend on the manifestation of the disease: If there are skin lesions,
send skin scrapings or pus. If there is pulmonary involvement, send sputum. Other specimens
include biopsy material, bronchial washings and urine. Occasionally, the organism can be
isolated from urine as B. dermatitidis often infects the prostate.
Most of the systemic fungi have a specific niche in nature where they are commonly found. This
organism survives in soil that contains organic debris (rotting wood, animal droppings, plant
material) and infects people collecting firewood, tearing down old buildings or engaged in other
outdoor activities, which disrupt the soil.
In addition to an ecological niche, most dimorphic fungi, which cause systemic infections, have a
limited geographic distribution where they occur most frequently. Blastomycosis occurs in
eastern North America, India and Africa. The vast majority of patients with blastomycosis in S.C.
are infected in the northern part of the state, above the Fall Line (Augusta, GA, Aiken, Columbia,
Cheraw, Raleigh, NC).
A specific gene (BAD-1) which appears to be a virulence factor for B. dermatitidis has recently
been described. Once the conversion to the yeast form begins BAD1 rapidly accumulates on the
surface of the yeast cell.
Mycology
If you request a fungus culture from the microbiology laboratory, the cultures will be incubated at
25ºC and at 37ºC because most of the significant systemic pathogenic fungi are dimorphic. A
culture of B. dermatitidis takes 2 to 3 weeks to grow at 25ºC. It appears as a white, cottony mold
(mycelium) on Sabouraud dextrose agar. Most specimens for fungus culture are plated on
Sabouraud's dextrose agar for the 25 C incubation. Microscopically, the mycelia and the fruiting
bodies (conidia) are evident. However, the mold cannot be identified by its fruiting bodies. The
fruiting bodies are called microconidia, but they are not distinctive. Other fungal saprophytes and
pathogens have similar conidia. At 37ºC the yeast form grows in about 7-10 days. It appears as
a buttery-like, soft colony with a tan color. Microscopically, we see the typical yeast form of a
THICK WALL and a SINGLE BUD with a WIDE BASE. This wide base is characteristic of B.
dermatitidis, and it is important to be able to recognize this morphology. The cells are 12-15
microns in diameter.
The yeast will convert to the mycelial form when incubated at 25ºC, taking from 3 to 4 days up to
a few weeks. Similarly, the mycelial growth can be converted to yeast form when incubated at
37ºC.
In the past, the only way to identify the dimorphic fungi was to convert from one form to the
other, but now it is possible to take the mycelial growth (which is the easiest to grow), and
confirm the isolate with a DNA probe in a matter of hour
Histopathology
B. dermatitidis produces both a granulomatous and suppurative tissue reaction. A typical
cutaneous lesion shows central healing with microabscesses at the periphery. The yeast forms
can frequently be demonstrated in a KOH preparation of pus from a skin lesion. A pus specimen
may be obtained by nicking the top of a microabscess with a scalpel, obtaining the purulent
material and making the diagnosis in 5 minutes by microscopic examination with KOH. This
organism has a characteristic appearance of a double contoured wall with a single bud on a
wide base.

Serology
There are three serological tests used for blastomycosis:
1. Immunodiffusion test (precipitin) It requires 2 to 3 weeks after onset of illness to become
 positive. This test is positive in about 80% of the patients with blastomycosis. When it is
positive, there is close to 100% specificity.
2. Complement fixation (CF) test. This test requires 2 to 3 months after the onset of disease to
develop detectable antibody. Besides the long delay before there is measurable antibody,
another disadvantage of the C-F is that it cross reacts with other fungal infections
(coccidioidomycosis and histoplasmosis). The advantage is that it is a quantitative test. The
physician can follow the patient's response to the disease by monitoring the antibody titer.
3. Enzyme Immunoassay (EIA). The test is easy to perform and antibody is detected early in the
disease process.
TREATMENT:
Itraconozole is the drug of choice for mild cases of blastomycosis while amphotericin B is used
for patients with life threatening disease. The new antimycotic, voriconazole is now being used.
HOUR 4
B. HISTOPLASMOSIS (Histoplasma capsulatum)
Histoplasmosis is a systemic disease, primarily of the reticuloendothelial system, manifesting
itself in the bone marrow, lungs, liver, and the spleen. In fact, hepatosplenomegaly is the
primary sign of infection in children, while in adults, histoplasmosis more commonly appears as
a pulmonary disease.
The lungs are the portal of entry. There is generally complete recovery from the acute pulmonary
form (another “flu-like” illness). In the endemic area the majority of patients who develop
histoplasmosis (95%) are asymptomatic. The diagnosis is made from their history, serologic
testing or skin testing. In the patients who are clinically ill, histoplasmosis generally occurs in
one of three forms: acute pulmonary, chronic pulmonary or disseminated. However, if untreated,
the disseminated form of disease is usually fatal.
Patients will first notice shortness of breath and a cough which becomes productive. The
sputum may be purulent or bloody. Patients will become anorexic and lose weight.
They have night sweats. These symptoms resemble tuberculosis, and the lung x- ray also looks
like tuberculosis with calcifications, but radiologists can distinguish between these diseases on
the chest film.
This is one of the most common fungal infections, occurring frequently in S.C., particularly the
northwestern portion of the state. The ecological niche of H. capsulatum is in blackbird roosts,
chicken houses, and bat guano. Typically, a patient will have spread chicken manure around his
garden, and 3 weeks later will develop pulmonary infection. There have been several outbreaks
in S.C. where workers used bulldozers to clear canebrakes which served as blackbird roosts. All
who were exposed, workers and bystanders, contracted histoplasmosis. Histoplasmosis is a
significant occupational disease in bat caves in Mexico when workers harvest the guano for
fertilizer.
Histoplasmosis is prevalent primarily in the eastern U.S. and parts of Central and South
America. In S.C., a histoplasmin skin test survey of lifetime, one county residents, white males,
17 to 21 years old, was performed on Navy recruits. The greatest number of positive skin tests
appeared in the northwestern part of the state. A similar study of medical students conducted at
MUSC about 30 years ago bore the same distribution (Goodman and Ever, J.S.C.M.A. 67:53-
55, 1971).
The skin test is NOT used for diagnostic purposes, because it interferes with serological tests.
Skin tests are reserved for epidemiological surveys.
Clinical specimens sent to the laboratory depend on the presentation of the disease; Sputum or
Bronchial alveolar lavage if its pulmonary disease, or Biopsy material from the diseased organ.
Bone marrow is an excellent source of the fungus, which tends to grow in the reticulo endothelial
system. Peripheral blood is also a source of visualizing the organism histologically. The yeast is
usually found in monocytes or in PMN's. Many times an astute medical technologist performing
a white blood cell differential count will be the first one to make the diagnosis of histoplasmosis.
In peripheral blood, H. capsulatum appears as a small yeast about 5-6 microns in diameter.
(Blastomyces is 12 to 15 microns). Gastric washings are also a source of H. capsulatum as
 people with pulmonary disease produce sputum and frequently swallow their sputum.
Mycology
When it is cultured on Sabouraud dextrose agar and incubated at 25ºC, H. capsulatum appears
as a white, cottony, aerial mycelium after 2 to 3 weeks. As the colony ages, it becomes tan. In
the mold form, Histoplasma has a very distinct spore called a tuberculate macroconidium (10-15
microns diameter). The tuberculate macroconidia are diagnostic, however there are some
nonpathogens that appear similar. A medical mycologist will be able to distinguish between
them.
Grown at 37ºC the yeast form appears. It is a soft, white to tan colony. The yeast cell is 5-6
microns in diameter and slightly oval in shape. This is not diagnostic. To confirm the diagnosis,
one must convert the organism from yeast to mycelium or vice-versa or use the DNA probe.
Serology for histoplasmosis is a little more complicated than for other mycoses, but it provides
more information than blastomycosis serology.
There are 4 serologic tests available:
1. Complement Fixation
2. Immunodiffusion
3. EIA (antibody)
4. EIA (antigen)
Each of these serological tests has different characteristics, which make them useful. The
complement fixation test is like the one for blastomycosis, except there are 2 antigens, one to
the yeast form of the organism and the other to the mycelial form. Some patients react to one
form and not the other, while some individuals react to both. The reason for the different
responses is not clear. One disadvantage is that complement-fixing antibody develops late in the
disease, about 2 to 3 months after onset. A second disadvantage is that it cross reacts with
other mycotic infections. An advantage of the C-F test is that it is quantitative, so the physician
can follow the course of the disease by observing the titer of several samples.
The interpretation of the immunodiffusion test is a little more complicated than with
blastomycosis because there are two bands which may appear. An H band indicates active
disease and will appear in 2 to 3 weeks. An M band can indicate past or present disease, or
result from a skin test. This is one reason why skin tests are not used for diagnosis because
they can interfere with other tests. Skin tests will also affect the complement fixation test.
The EIA test for the detection of antigen is only available in the author’s laboratory but it appears to be
sensitive in detecting systemic histoplasmosis.
The drugs of choice (DOC) are Itraconazole (static) for mild disease and amphotericin B for
severe disease (cidal).
C. COCCIDIOIDOMYCOSIS (Coccidioides immitis)
Coccidioidomycosis is primarily a pulmonary disease. About 60 % of the infections in the
endemic area are asymptomatic. About 25 % suffer a “flu-like” illness and recover without
therapy. This disease exhibits the typical symptoms of a pulmonary fungal disease: anorexia,
weight loss, cough, hemoptysis, and resembles tuberculosis. In addition, arthralgia and
erythema nodosum (particularly on the legs) is frequently seen in female patients. CNS infection
with C. immitis is more common in coccidioidomycosis while it is less frequent with the other
fungal diseases. There is a much greater mortality rate in dark-skinned people (Mexicans,
Filipinos, and Blacks). They are 25 times more likely to develop progressive disease and death.
The reason for this is obscure.
Geographic Distribution
The ecological niche of C. immitis is the Sonoran desert, which includes the deserts of the
Southwestern USA (California, Arizona, New Mexico, Nevada, Utah and Texas) and

northern Mexico. It is also found in small foci in Central and South America. Desert soil, pottery,
archaeological middens, cotton, and rodent burrows all harbor C. immitis.
C. immitis is a dimorphic fungus with 2 life cycles. The organism follows the SAPROPHYTIC
 cycle in the soil and the PARASITIC cycle in man or animals. The saprophytic cycle starts in the
soil with spores (arthroconidia) that develop into mycelium. The mycelium then matures and
forms alternating spores within itself. The arthroconidia are then released, and germinate back
into mycelia. The parasitic cycle involves the inhalation of the arthroconidia by animals or man,
which then form into spherules, which become filled with endospores. The ambient temperature
and availability of oxygen appear to govern the pathway. The spores of the organism are readily
airborne and can be carried by the wind and therefore spread hundreds of miles in storms so the
distribution is quite wide. In 1978 cases were seen in Sacramento 500 miles north of the
endemic area, from a dust storm in Southern California. .
.
The cases that occur in South Carolina are usually in patients who have visited an endemic area
and brought back pottery, or blankets purchase from a dusty roadside stand, or in Navy and Air
Force personnel who were exposed when they were stationed in the endemic area. The disease
manifests itself after they are transferred to a base in South Carolina. A few interesting cases
occurred in cotton mills in Burlington and Charlotte, N.C. The cotton, grown in the desert of the
Southwest, was contaminated with the fungus arthroconidia and the mill workers inhaled the
spores while handling the raw cotton and developed coccidioidomycosis.
Clinical Specimens
Clinical specimens include sputum, pus from skin lesions, gastric washings, CSF, and biopsy
material from skin lesions.
Mycology
C. immitis is a dimorphic fungus. Cultured on Sabouraud's agar at 25ºC it grows as a mold in 2
to 3 weeks. Characteristically, the mycelia develop arthroconidia. ("By their fruits ye shall know
them"). It is a barrel-shaped (smaller at the edges, wider at the middle) asexual spore. Typically,
the arthroconidia alternate with non spore-forming cells in the mycelium.
When grown in vitro at 37ºC there is no yeast form!! C. immitis is a dimorphic fungus; in vivo
(pus or tissue) one sees the pathogenic or invasive form – which is a spherule. The organism
develops into spherules (30-60 microns) that are filled with endospores which are 3 to 5 microns
in diameter. A spherule will develop endospores within, then break apart, releasing the
endospores. This is the tissue form seen in pus or histological sections: spherules and loose
endospores. They can also be seen in a KOH preparation of sputum. It is pathognomonic for
coccidioidomycosis.
Serology
There are four tests for diagnosis:
1. Complement-Fixation
2. Slide agglutination
3. Immunodiffusion
4. EIA
C-F antibody is slow to rise and develops in about 1 month after exposure. This test is excellent
for coccidioidomycosis because it is quantitative. However, these antibodies cross-react with
some other fungi (Blastomyces and Histoplasma) but this is not a problem in the endemic area.
The C-F test is also a PROGNOSTIC test. If the titer keeps rising, then the patient is responding
poorly and the course may be fatal. If the C-F titer is dropping then the prognosis for that patient
is favorable. A titer of greater than 1:128 usually indicates extensive dissemination.
Life-long immunity usually follows infection with C. immitis.
Fluconazole and itraconazole are the drugs of choice with amphotericin B reserved for more
severe infections
D. PARACOCCIDIOIDOMYCOSIS (Paracoccidioides brasiliensis)
This is a chronic granulomatous disease of mucous membranes, skin, and pulmonary system.
This disease occurs from the middle of Mexico (North America) to Central and South America.
The ecological niche of this organism is probably the soil. The disease is more common in warm
and moist climates.
A common triad of symptoms that are seen in Latin America is pulmonary lesions, edentulous
mouth, and cervical lymphadenopathy. Prior to the recognition of this disease, patients in
Latin America with paracoccidioidomycosis were often sent to tuberculosis sanitaria, just as
patients with histoplasmosis were in the U.S. The organisms invade the mucous membranes of
the mouth causing the teeth to fall out. White plaques are also found in the buccal mucosa, and
this along with the triad is now used to clinically differentiate clinically between tuberculosis and
paracoccidioidomycosis. There are probably asymptomatic cases in the endemic area.
This disease has a long latency period. 10-20 years may pass between infection and
manifestation of the infection in the non-endemic areas of the world. Typically, a case of
paracoccidioidomycosis seen in the U.S. occurs in someone who worked in South America for
some period of time, returned to the U.S. and years later develop this disease. The patient does
not realize the importance of this past history. Almost all diagnoses of fungal diseases depend
upon careful questioning and a probing history.
The clinical material which should be sent to the laboratory for examination is sputum, biopsy
material, pus, and crust from the lesions. Examination of sputum or crust from one of the lesions
with KOH reveals a yeast because this is a dimorphic fungus. In contrast to the other yeasts,
particularly blastomyces, paracoccidioides has MULTIPLE BUDS, a THIN CELL WALL, and a
NARROW BASE.
Mycology
At 25º C, the colony is a slow-growing dense, white mycelium, not loose and cottony like the
other endemic mycoses. On Sabouraud's agar it takes 2-3 weeks to grow. The mycelium
adheres to the medium and the septate hyphae have terminal or intercalated
spores which are not diagnostic. When cultured at 37º C, the yeast is slow growing with a white
tan, cerebriform, thick colony. Microscopically, these yeasts appear as described above ranging
in size from 5 to 15 microns. The cells show the pathognomonic single or multiple buds with a
narrow base.
Histopathology
Histologically, one sees multiple buds on the mother cell forming a "Captain's wheel." This is
diagnostic of paracoccidioidomycosis. In this case, the mother cell is 40-50 microns in diameter
and the buds are 2-5 microns in size.
Serology
The best serological test for paracoccidioidomycosis is the immunodiffusion test. It is better than
99% specific and almost 85% sensitive.
Therapy
The D.O.C. is amphotericin B. Sulphonamide-trimethoprim is also used. Presently Itraconazole
appear to provide the best recovery.
E. SPOROTRICHOSIS (Sporothrix schenckii)
Sporotrichosis is usually a chronic infection of the cutaneous or subcutaneous tissue, which
tends to suppurate, ulcerate and drain. In recent years, a pulmonary disease has been seen
more frequently. Occasionally, infection with S. schenckii may result in a mycetoma.
Sporotrichosis is caused by another dimorphic fungus. The infection is also known as "rose
growers disease." The ecologic niche for this organism is plant material (rose thorns, sphagnum
moss, timbers) and soil. A study on the occupational distribution of sporotrichosis showed that
forest employees accounted for 17% of the cases, gardeners and florists, 10%; and other soil
related occupations another 16%. Sporotrichosis occurs worldwide.
Every aspect of this disease (clinical, pathology, mycology, ecology) was investigated during an
epidemic of 3,000 patients in a gold mine in South Africa during the 1940's. The mold was
growing on mine timbers and every time a worker bruised himself on the timber, the spores were
inoculated and a lesion developed. Patient history is very important in this disease also. It is
often seen in gardeners and begins with a thorn prick on the thumb. A pustule develops and
ulcerates. It infects the lymphatic system and then the disease progresses up the arm with
ulceration, abscess formation, break down of the abscess with large amounts of pus followed by
healing. Progression usually stops at the axilla.
Geographical distribution: Worldwide.
 Clinical material to be sent to the laboratory may be pus, biopsy material, or sputum from
pulmonary patients. The yeast form of this fungus in tissue or in culture, can be round
(6-8 um) or fusiform. The fusiform shape is not the usual form but if a cigar-shaped yeast is
observed in tissue, it is usually diagnostic of sporotrichosis.
Mycology
At 37° C Sporothrix grows as a white pasty yeast with small round to oval forms (3-10 um). At
25º C this colony is white-cream and very membranous, but as it ages (2-3 weeks) it becomes
black and leathery. Microscopically, the mycelium is branching, septate and very delicate, 2-3
um in diameter. The pyriform conidia, 2-4 um, form a typical arrangement in radial groups at the
end of a conidiophore called "daisies."
Histopathology
S. schenckii stains poorly with the usual histopathological stains (H&E). If sporotrichosis is
suspected, the pathologist must be informed so he can use special stains. Histologically asteroid
bodies, a tissue reaction (also known as Splendori reaction) may be seen around the yeast cell.
Serologic tests are not commercially available.
The drug of choice for the cutaneous form and the systemic form is itraconazole.
HOUR 5
VII. OPPORTUNISTIC MYCOSES
Opportunistic mycoses are infections due to fungi with low inherent virulence. These pathogens
are an almost limitless number of fungi. The etiologic agents are organisms which are common
in all environments. The host/pathogen equilibrium is as follows:
Number of organisms x Virulence = Disease
Host resistance
With opportunistic infections the equation is tilted in favor of "disease" because the host
resistance is lowered. For the immunocompromised host, there is no such thing as a non
pathogenic fungus. The fungi most frequently isolated from immunocompromised patients are
saprophytic (i.e. from the environment) or endogenous (a commensal). The most common
species are Candida sp., Aspergillus sp., and Mucor sp.
The upward trend in the diagnoses of opportunistic mycoses reflects increasing clinical
awareness by physicians, improved clinical diagnostic procedures and better laboratory
identification techniques. Another important factor contributing to the increasing incidence of
infections with fungi that have not been previously known to be pathogenic has been the rise in
the number of immunocompromised patients who are susceptible
hosts for the most uncommon agents. Patients with primary immunodeficiencies are susceptible
to mycotic infections particularly when cell-mediated immunity is compromised. In addition,
several types of secondary immunodeficiencies may be associated with an increased frequency
of fungal infections. More invasive diagnostic and therapeutic techniques also contribute to
potential infections.
When a fungus is isolated from an immunocompromised patient, the attending physician has to
distinguish between: 1) colonization (which is of no major concern), 2) transient fungemia
(often involving C. albicans) and 3) systemic infection. A great deal of clinical judgment is
required to reach these conclusions, which imply important therapeutic decisions, such as the
institution of therapy.
Causes of immunodeficiency commonly encountered:
Malignancies. (Leukemias, lymphomas, Hodgkin's disease). Certain malignancies predispose to certain
infections (bacterial or fungal). In one study of cancer patients, fungal septicemia and
pneumonias accounted for almost a third of deaths.
Drug therapies. Anti-neoplastic substances, steroids, immunosuppressive drugs.
tibiotics. Over-use or inappropriate use of antibiotics can also contribute to the development of fungal
infections by altering the normal flora of the host and facilitating fungal overgrowth or by
selecting for resistant organisms.
Therapeutic procedures can predispose for fungal infections:
1. Solid Organ and Bone Marrow transplantation
 2. Open heart surgery
3. Indwelling catheters (urinary, I.V. drugs or parenteral hyperalimentation). In cases of
fungemia, the contaminated catheter must be removed before starting anti-fungal
therapy.
4. Artificial heart valves can be colonized by a variety of infectious agents, including Candida
species. In a case of Candida infection of an artificial heart valve, antifungal
treatment is only efficient if the infected valve is replaced.
5. Radiation therapy.
Other factors associated with increased frequency of mycotic infections:
1. Severe burns
2. Diabetes
3. Tuberculosis
4. I.V. drug use
AIDS. Virtually all AIDS patients will have a fungal infection sometime during the course of disease. Certain
fungi may be frequently associated with some of the predisposing factors listed above.
However, any one of the ubiquitous saprophytes (most of which do not cause disease in
immunocompetent hosts) as well as occasional pathogens may cause disease in these
patients. In the last few years, the use of HAART therapy for AIDS has reduced the number of
fungal infections in these patients.
Biofilm Formation: It has long been recognized that in patients with a microbial infection, any
artificial device such as an indwelling catheter or prosthetic valve, must be removed prior to
initiating antibiotic therapy. The foreign body will act as a nidus, seeding the infection if it
remains present. The exact mechanism was not clear. A biofilm is a microcolony of organisms
with a polysaccharide slime, which adheres to a surface (catheter, implant, or dead tissue) and
which resist removal by fluid movement and the organisms are resistant to antimicrobials. The
slime may contain a single species of organism or be polymorphic. This biofilm phenomenon,
which occurs on the rocks in a stream, was first recognized as a public health problem in
drinking water distribution pipes and was regarded as a source of coliform contamination of
drinking water. Recent work in clinical microbiology has shown that biofilms occur in the human
and animal body. These organisms develop a resistance to therapy because they are contained
in a matrix, which acts like a tissue and becomes a barrier to antibodies, macrophages and
antimicrobial agents. Candida species readily form biofilms.
UNUSUAL CLINICAL PRESENTATION
The diagnosis of opportunistic infections requires a high index of suspicion. Without this
curiosity the clinician may not consider mycotic infections in the compromised patient because:
1. Patients present with atypical signs and symptoms.
2. Fungi have an unusual organ affinity
3. The systemic mycoses may occur outside the known endemic area. 4.
Unusual histopathology
5. The etiological agent may be considered a saprophyte or contaminant.

1. Atypical signs and lesions.

Malassezia furfur usually causes a rather benign and self-limited disease in normal hosts
(Tinea versicolor), but in immunocompromised patients may show a rash with disseminated
disease and sepsis. This organism requires long-chain fatty acids for growth. Patients
receiving parenteral fat emulsions for nutrition become a walking petri plate.
2. Unusual Organ affinity.
Candida may invade liver, heart valves; Oral thrush occurs in people who are relatively
immunocompetent while esophageal candidiasis occurs in those patients who are
immunologically compromised. Some other species of Candida are: glabrata, krusei,
torulopsis, parapsilosis, dubliensis, etc.
Cryptococcus may cause pulmonary and cutaneous infections. Studies show that from 10 %
to 30 % of AIDS patients have cryptococcal meningitis and they will require maintenance
 therapy with fluconazole for the remainder of their life. Fluconazole penetrates the CSF
Mortality: Without treatment 100%
With treatment 20%
Relapse:
Non-AIDS 15-20%
AIDS patients 50%
With relapse there is 60% mortality.
Sporotrichosis: Co-infection with other fungi or TB is frequent
Blastomycosis: More frequently disseminated and all patients have done very poorly.
There has been one report on 15 cases of blastomycosis in AIDS patients. Six patients
(40%) had CNS involvement. Usually CNS disease only occurs in 3-10% of the patients.
Aspergillosis
Mortality: With amphotericin B 72%
Without amphotericin B 90%
3. Infections with systemic dimorphic fungi occurring outside endemic areas.
These factors complicate the diagnosis and management of these diseases.
Coccidioidomycosis
Mycelial forms seen in tissue. Occurs in patients outside the endemic area. Patients require
fluconazole or itraconazole maintenance therapy.
Histoplasmosis
Occurs in patients outside the endemic area and they require fluconazole or itraconazole
maintenance therapy
• All cases are disseminated.
• Relapse rate is > 50%
• Rapidly fatal in 10%.

4. Unusual Histopathology.
Even the inflammatory reaction may be different in biopsy specimens. The normal host
reaction to fungal invasion is usually pyogenic or granulomatous. In the immunodeficient
host the reaction is necrotic.
5. Unusual Pathogens
Penicillium marneffei
Endemic in southeast Asia. Dimorphic. A small yeast form resembling Histoplasma
capsulatum and reproducing by fission. The mycelial for produces a red pigment. Therapy
requires amphotericin B and oral itraconazole maintenance.
Pneumocystis jiroveci
A common cause of pneumonia in AIDS patients and the most common opportunistic
infection in these patients. Formerly thought to be a protozoon. Recently shown to be a
fungus. Not able to grow in vitro.
Table. Some common associations between fungal organisms and disease conditions.
Cryptococcus
Mucormycete
neoformans Candida albicans Candida (Torulopsis)
glabrata s Aspergillus species

Diabetes mellitus Prolonged antibiotic Diabetes mellitus Intravenous Leukemias

Tuberculosis therapy Hyperalimentation catheters Corticosteroid
Lymphoma Prolonged Immunosuppressio Diabetes therapy
Hodgkin's disease intravenous n mellitus Tuberculosis
Corticosteroid catheters Cytotoxic drugs Leukemias Immunosuppressio
therapy Prolonged urinary Immunosuppressio Corticosteroid n
Immunosuppressio catheters n therapy I.V. drug abuse
n Corticosteroid Diabetes mellitus Intravenous therapy
therapy Hyperalimentation Severe burns
IMPROVING TREATMENT:
1. New drugs – Lipid Amphotericin B, Third generation azoles (posaconazole, voriconazole)
2. New therapeutic regimen – Combination therapy.
3. Aggressive therapy
• Prophylactic – Before chemotherapy; Posaconazole now approved
• Empirical – Patient at risk
• Pre-emptive – Some evidence of fungal infection
4. Conjunctive therapy
• Monoclonal antibody plus antifungal agent
• Immunotherapy plus antifungal agent.
MEDICAL MYCOLOGY GLOSSARY
ACTIDIONE - Trademark name for cycloheximide, a selective antifungal agent.
AERIAL - mycelium: Hyphal units above the colony agar interface.
ANAMORPH - A somatic or reproductive structure that originates without nuclear recombination
(asexual reproduction). Cf. Teleomorph.
ANTHROPOPHILIC - A fungus (dermatophyte) that preferentially grows on man rather than
other animals or the soil.
ARTHROCONIDIUM - (pl. arthroconidia) A thallic conidium released by the fragmentation or
lysis of hypha. It is not notably larger than the hypha from which it was produced, and separation
occurs at a septum.
ARTHROSPORE - See arthroconidium.
ASTEROID BODY -(Splendore-Hoeppli phenomenon) An eosinophilic substance which forms a
covering of approximately 10 microns thick around a basophilic yeast especially in
sporotrichosis.
BASE - The junction of a bud and the mother cell of a yeast.
BIOFILM – Microcolonies of organisms which adhere to a surface (catheter, implant, water pipe,
blood vessel) and which resist removal by fluid movement and have a decreased susceptibility
to anti-microbials.
BUD - A type of asexual reproduction commonly found in yeasts.
CAPSULE - A hyaline mucopolysaccharide covering around the cell body of certain yeasts
(Cryptococcus, Rhodotorula) and some spores and conidia.
CHLAMYDOSPORE - Thick-walled resistant resting spore, especially in Histoplasma
capsulatum. See macroconidium.
COENOCYTIC - Without septa.
COLONIZATION - growth of an organism in a host without tissue invasion. COLUMELLA - A
sterile invagination of a sporangium, as in the Mucormycetes. COMMENSALISM - A symbiotic
relationship in which there is no damage to either participant. COMPLEMENT FIXATION - A
serologic procedure to determine antibody to fungus infections. Cross reacts with other systemic
fungi but is a quantitative test.
CONIDIOGENOUS CELL - The cell that gives rise to a conidium.
CONIDIUM (pl. conidia) - A reproductive propagule produced in the absence of nuclear
recombination, thus representing anamorphic or asexual reproduction.
CONIDIOPHORE - A specialized hypha that gives rise to, or bears a conidium.
CYCLOHEXIMIDE - See Actidione.
DERMATOMYCOSIS - An infection of hair, skin and nails caused by the keratinophilic fungi of
the genera Trichophyton, Microsporum and Epidermophyton which infect hair, skin and nails.
DERMATOPHYTE - Infection of hair, skin and nails caused by fungi other than dermatophytes.
DEMATIACEOUS - A fungus having brown or black melanotic pigment in the cell wall.
DICHOTOMOUS - A type of branching of hyphae that is frequent and repetitious; the two
branches are approximately equal in size.
DIMORPHIC - Having two forms.
DISEASE – The presence of microorganism in the body with a pathologic effect. (see infection).
ECHINULATE - Covered with delicate spines.
ECOLOGY - The science of organisms as affected by the factors of their environment.
ECTOENDOTHRIX - Arthroconidia formed on the outside and inside of a hair shaft.
ECTOTHRIX - Forming a sheath of arthroconidia on the outside of a hair shaft. The cuticle of the
hair is destroyed.
EDENTULOUS - The absence of teeth.
ENDOGENOUS - From within.
ENDEMIC - A disease which occurs in a limited geographic area.
ENDOSPORE - A spore formed within some other unit, such as in a spherule. (Typical of
Coccidioidomycosis).
ENDOTHRIX - Arthroconidia formed inside a hair shaft. The cuticle of the hair remains intact.
EXOGENOUS - From without. The source of most mycotic infections is exogenous, i.e. outside
the body (the environment).
FLOCCOSE - Cottony or wooly.
FOMITE - A substance other than food that may harbor and transmit infections organisms.
FRUITING BODY - Reproductive structures of fungi. (Spores).
FUNGEMIA - Presence of fungi in the blood.
GMS - Gomori methenamine-silver. An excellent stain for visualizing fungi. The cell wall stains
black and the background is green. Advantage: stains all fungi.
Disadvantage: the tissue reaction is not visible.
GEOPHILIC - Soil-seeking, having a soil reservoir.
GERM TUBE - Initial hypha from a sprouting conidia, spore or yeast.
GLABROUS - Smooth.
H & E - Hematoxylin and Eosin. A stain used routinely for general pathology. Most fungi are
visible, but not distinctive. Fungal walls usually stain blue or purple. Other cells stain pink.
Advantage: the tissue reaction is visible.
HYALO - Colorless; also hyaline.
HYPHA (pl. hyphae) - A vegetative filament of a fungus.
HYPHOMYCETE - An fungus that produces mycelium with or without discernible dark pigment
in the cell walls. If the hypha is pigmented, it is called dematiaceous; if colorless, hyaline.
IMMUNODIFFUSION - A serologic test to determine the presence of antibody by double
diffusion precipitation in auger.
INCIDENCE - The number of new cases of a disease occurring during a specific period.
INCUBATION PERIOD - The time between an infectious agent entering the body and the onset
of clinical symptoms.
INDURATED - Hard.
INFECTION - The presence of microorganisms in the body without evidence of pathology (see
disease).
INTERCALARY - Formed within a hyphal unit.
INVASIVE - The entrance and growth of an organism in tissue.
LATEX AGGLUTINATION - A simple serologic procedure to detect antibody by the clumping of
antigen coated particles.
MACROCONIDIUM - The larger of two types of conidia produced in the same manner by the
same fungus.
MICROCONIDIUM (pl. microconidia) - The smaller of two types of conidia produced in the same
manner by the same fungus.
MOLD - See Mycelium.
MURIFORM - Like a wall; multicellular, with transverse and longitudinal septations.
MYCELIUM - The mass of hyphae making up a fungus colony.
MYCOLOGY - The study of fungi.
ORGANOTROPISM - The predilection of a fungus to invade a particular organ.
PHAEO - Darkly pigmented.
PREVALENCE - The total number of cases of a disease in existence at a certain time in a
designated area.
PROBE – A specific nucleic acid sequence (known) used to detect a complimentary sequence
in an unknown fungus.
PSEUDOHYPHA (pl. pseudohyphae) - A fragile string of cells that result from the budding of
blastoconidia that have remained attached to each other. The septa separating the cells are
complete and there is no cytoplasmic connection, as is found in most true septate hypha.
RHIZOID - A root like structure. Used in the identification of some Mucormycetes. RESERVOIR
- A permanent host or carrier from which infection is spread. SAPROBE - An organism which
requires organic material as a source of energy. SAPROPHYTE - See Saprobe.
SCLEROTIC BODY - (sclerotic cell). The tissue form (yeast-like) of most agents of
chromomycosis. Dark brown, single or in short chains, occasionally septate, 5 - 15 microns in
diameter.
SENSITIVITY - The ability to detect all patients with a specific disease.
SEPTUM (pl. septa) - A cross wall.
SEROLOGY - The study of antigens or antibodies in peripheral blood to support, confirm or rule
out certain diseases.
SOURCE - The clinical specimen most likely to yield the etiologic agent. ALSO The ecologic
niche or natural nidus of the etiologic agent.
SPECIFICITY - The capacity to identify a disease correctly.
SPINOSE - Covered with small spines.
SPORANGIOPHORE - A specialized hypha that gives rise to a sporangium.
SPORANGIOSPORE - A reproductive unit formed in a sporangium.
SPORANGIUM - A cell within which spores are borne by progressive cleavage. SPORE - A
reproductive propagule produced internally by "free cell" formation, as in the ascomycete, i.e.,
complete spores formed all at once around the nuclei available or by "progressive cleavage," as
in a sporangium.
STOLON - Hypha from which rhizoids and sporangiophores are produced, as in the genus
Rhizopus.
SYNONYM - Another (especially a later or illegitimate) name for a species or taxonomic group.
TELEOMORPH - The sexual state of a fungus.
TERMINAL - Formed at the end of a structure.
TINEA - Literally "moth". A clinical term meaning "ringworm".
THERMOTOLERANT - Ability to grow at high temperatures (usually above 42 C).
TUBERCULATE - Spines or finger-like projections on macroconidia, characteristic of
Histoplasma capsulatum.
VESICLE - A swollen or bladder-like cell.
VIRULENCE - Degree of pathogenicity; the disease producing capacity of an organism.
YEAST - A unicellular fungus, usually round or ovoid, that reproduces by budding.
ZOOPHILIC - Infecting lower animals rather than man.
The glossary was derived from several sources including: Rippon, Medical Mycology, Third
Edition; Emmons, Binford, Utz, and Kwon-Chung, Medical Mycology, third Edition; Ainsworth &
Bisby's Dictionary of the Fungi, Seventh Edition; and other keen authorities.