Staphylococcus
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Azwa AlimanStaphylococcus
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Azwa AlimanSTAPHYLOCOCCUS
STAPHYLOCOCCUS
• Gram-positive cocci that grow in a
characteristic pattern resembling a cluster
of grapes.
• Most staphylococci are large, 0.5 to 1.5 µm
in diameter, and
• Non motile
• Able to grow in a variety of conditions
– aerobically and anaerobically
- temperature 18' - 40'C
STRUCTURE
EPIDEMIOLOGY
Normal flora on human skin and mucosal surfaces.
Organisms can survive on dry surfaces for long periods- (because of
thickened peptidoglycan layer and absence of outer membrane)
Person to person spread through direct contact or exposure to contaminated formites (eg;
bed lines , clothing)
Risk factors include presence of foreign body (eg splinter,suture,prothesis,catheter),
previous surgical procedure, and use of antibiotics that suppress the normal
microbial flora
EPIDEMIOLOGY
Patient at risk for specific diseases include infants (scalded skin syndrome), young
children with poor personal hygiene (impetigo and other cutaneous infections),
menstruating women (TSS), patients with intravascular catheters (bacteremia and
endocarditis) or shunts (meningitis), and patient with compromised pulmonary
function or antecedent viral respiratory infection (pneumonia).
MRSA now the most common cause of community - acquired skin and soft
tissue infections.
CLINICAL
DISEASES
CLINICAL SUMMARIES
STAPHYLOCOCCUS AUREUS
Toxin-Mediated Diseases
• Scalded skin syndrome: Disseminated desquamation of epithelium in infants;
blisters with no organisms or leukocytes
• Food poisoning: After consumption of food contaminated with heatstable
enterotoxin, rapid onset of severe vomiting, diarrhea, and abdominal cramping,
with resolution within 24 hours
• Toxic shock: multisystem intoxication characterized initially by fever,
hypotension, and a diffuse, macular, erythematous rash; high mortality without
prompt antibiotic therapy and elimination of the focus of infection
Suppurative Infections
• Impetigo: localized cutaneous infection characterized by pus-filled vesicle on an
erythematous base
• Folliculitis: impetigo involving hair follicles
• Furuncles or boils: large, painful, pus-filled cutaneous nodules
• Carbuncles: Coalescence of furuncles with extension into subcutaneous tissues and
evidence of systemic disease (fever, chills, bacteremia)
• Bacteremia and endocarditis: Spread of bacteria into the blood from a focus of
infection; endocarditis characterized by damage to the endothelial lining of the heart
• Pneumonia and empyema: Consolidation and abscess formation in the lungs; seen in
the very young and elderly and in patients with underlying or recent pulmonary
disease; a severe form of necrotizing pneumonia with septic shock and high mortality is
now recognized
• Osteomyelitis: Destruction of bones, particularly the metaphyseal area of long bones
• Septic arthritis: Painful erythematous joint with collection of purulent material in the
joint space
COAGULASE-NEGATIVE STAPHYLOCOCCUS SPECIES
• Wound infections: Characterized by erythema and pus at the site of a
traumatic or surgical wound; infections with foreign bodies can be
caused by S. aureus and coagulase-negative staphylococci
• Urinary tract infections: Dysuria and pyuria in young sexually active
women (S. saprophyticus), in patients with urinary catheters (other
coagulase-negative staphylococci), or following seeding of the urinary
tract by bacteremia (S. aureus)
• Catheter and shunt infections: Chronic inflammatory response to
bacteria coating a catheter or shunt (most commonly with
coagulasenegative staphylococci)
• Prosthetic device infections: Chronic infection of device characterized by
localized pain and mechanical failure of the device (most commonly with
coagulase-negative staphylococci)
SPECIMENS:
• Pus and swabs from
infected sites
• Blood for culture
LABORATORY • Sputum
DIAGNOSIS • Cerebrospinal fluid
• Faeces, vomit and the
remains of food when
food poisoning is
suspected.
Microscopy
Gram positive cocci in cluster
Culture
• Blood agar, chocolate (heated blood) agar:
S. aureus produces yellow to cream or
occasionally white 1–2 mm in diameter
colonies after overnight incubation.
Pigment is less pronounced in young
colonies. Some strains are betahaemolytic
when grown aerobically. Colonies are
slightly raised and easily emulsified.
Identification of
Isolates
API STAPH
API STAPH
Reagents/ Material Mc Farland Incubation Usual identifiable
organisms
API Staph Medium 6ml 0.5MF 36'C +/- 2'C Staphylococcus
Mineral oil epidermidis
VP 1 + VP 2 Staphylococcus
NIT 1 + NIT 2 saphrophyticus
ZYM A Staphylococcus capitis
ZYM B Staphylococcus xylosus
Staphylococcus lentus
CLSI 2020
MANAGEMENT
1. SOURCE CONTROL
• - surgical or procedural mx of infected site
• -include incision and drainage or removal of infected
prosthetic devices
2. ANTIMICROBIAL THERAPY
• Selection of theraphy depends on culture and susceptibility
results
• EMPIRIC TREATMENT
MSSA MRSA
• Generally consists of beta- • Vancomycin
lactam agent
• -risk of nephrotoxicity
• Eg oxacillin, nafcillin, Click to add text
• -requires serum
cefazolin
concentration monitoring
• If isolate is penicillin
• Daptomycin
sensitive, penicillin is drug of
choice
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