Urinary Tract Infection

1
2 Introduction
 3

 Acute infections of the urinary tract fall into two

general anatomic categories:

Lower tract infection (urethritis and cystitis) and

Upper tract infection (acute pyelonephritis,

prostatitis)

 Infections of the urethra and bladder are often

considered superficial (or mucosal) infections, while
prostatitis and pyelonephritis signify tissue invasion.
 4 Cont.

 Uncomplicated UTI refers to acute cystitis or pyelonephritis

in:
 Non-pregnant outpatient women
 Without anatomic abnormalities
 Without instrumentation of the urinary tract
 UTI in male is not uncomplicated since it is rare and most
often involve structural abnormalities
 Recurrent UTI is not necessarily complicated
 5 Cont.
 UTIs:
 Catheter-associated (or nosocomial) vs non-catheter-
associated (or community-acquired)
 Symptomatic Vs asymptomatic

 asymptomatic bacteriuria: when there is significant bacteriuria

(more than 105 bacteria/mL ) in the absence of symptoms

 symptomatic abacteriuria: consists of symptoms of frequency and

dysuria in the absence of significant bacteriuria

 Commonly with chlamydia infections

 6 Cont.
 from a microbiologic, UTI exists when pathogenic microorganisms

are detected in the urine, urethra, bladder, kidney, or prostate.

 in most instances, growth of ≥105 /ml organisms from a properly

collected midstream "clean-catch" urine sample indicates infection.

 However, significant bacteriuria is lacking in some cases of true UTI.

 Especially in symptomatic patients, fewer bacteria (102–104/mL) may

signify infection.
 7 Cont.

 In urine specimens obtained by suprapubic aspiration or

"in-and-out" catheterization and in samples from a patient
with an indwelling catheter, colony counts of 102–104/mL
generally indicate infection.

 Conversely, colony counts of >105/mL in midstream urine

are occasionally due to specimen contamination, which is
especially likely when multiple bacterial species are found.
 8 Epidemiology
 Prevalence of UTIs varies with age and gender.

 neonatal boys are five to eight times more likely to have

UTIs(Vescio-ureteral reflux )

 Between the ages of 1 and 6 years, UTIs occur more frequently

in females.

 The vast majority of acute symptomatic infections involve

young women.

 The development of asymptomatic bacteriuria is rare among

men under 50 but common among women between 20 and 50.
 9 Etiology
 Uncomplicated infection

 Gram-negative bacilli. Escherichia coli causes 80%-90% of

community acquired infection

 Other causative organisms

 Proteus and Klebsiella spp, P.aurginosa and Enterobacter spp.,

account for a smaller proportion of uncomplicated infections.

 Complicated infection:

 E.coli ~ 50%, Proteus spp., K. pneumoniae, Enterobacter spp.,

P. aeruginosa, staphylococci, and enterococci
10 Cont.
 VRE have become more widespread, especially in patients
with long-term hospitalizations or underlying malignancies.

 Candida spp., are common causes of UTI in the critically ill

and chronically catheterized patient.

 Most UTIs are caused by a single organism; however, in

patients with stones, indwelling urinary catheters, or
chronic renal abscesses, multiple organisms may be isolated
11 Pathophysiology
 Route of infection is via three routes

 ascending, hematogenous (descending), and lymphatic pathways

Ascending Pathway

 Involved when bacteria colonizing the urethra subsequently travel

upwards, or ascend, the urethra to the bladder and cause cystitis and

continue to ascend to the ureters and cause pyelonephritis

 Women are at high risk of UTI due to

 The short length of the female urethra and its proximity to the

perirectal area
12 Cont.
 the use of spermicides and diaphragms as methods of
contraception

 Massage of the female urethra and sexual intercourse allow

bacteria to reach the bladder

Hematogenous Pathway

 involved through the seeding of the urinary tract with pathogens

carried by the blood supply

 S.aureus bacteremia can cause renal abscesses via the hematogenous

route

 E. coli and P. aeruginosa are less likely to seed the kidneys via
 13 Cont.

Three factors determine the development of

infection:

1. The size of the inoculum

2. The virulence of the microorganism, and

3. The competency of the natural host defense

mechanisms
14 Cont..
Host Defense Mechanisms
 Under normal circumstances, bacteria placed in the bladder
are rapidly cleared,
Þ through the flushing and dilutional effects of voiding
Þ as a result of the antibacterial properties of urine and
the bladder mucosa.
 The introduction of bacteria into the bladder stimulates
micturition with increased diuresis and efficient emptying
of the bladder
16 Risk factors
 Sexual-intercourse prostatic
hyperplasia

 Urologic-instrumentation,

 Urethral catheterization

 Urinary tract obstruction

 Use of a cervical diaphragm/spermicidal

 Diabetes

 Pregnancy
 17 Risk factors
 Use of spermicidal cpds with a diaphragm alters the normal
bacterial flora and has been associated with marked
increases in vaginal colonization with E. coli
 Decreased ureteral tone
 Decreased ureteral peristalsis
 Temporary incompetence of the vesicoureteral valves
result in urinary stasis and reduced defenses against
reflux of bacteria to the kidneys
 18 Clinical presentation

Cystitis
dysuria, frequency, urgency, and supra-pubic pain
urine often becomes grossly cloudy and malodorous and
is bloody
white cells and bacteria in urine
N:B temperature of >38.3°C (>101°F), nausea, and
vomiting, usually indicate concomitant renal infection,
as does CVAT
 19
Cont.

Acute Pyelonephritis
High fever, shaking chills, nausea, vomiting, abdominal
pain, and diarrhea.
Tachycardia, and generalized muscle tenderness
Marked tenderness on deep pressure in one or both
costo-vertebral angles or on deep abdominal palpation.
Leukocytosis and bacteria detectable in Gram-stained
urine
20 Cont.

 Urethritis
Dysuria
Frequency
 pyuria
 Elderly patients: altered mental status, change in eating
habits, or gastrointestinal symptoms.
 21 Diagnosis
Physical Examination

 upper UTI: costoveretbral tenderness

Laboratory Tests

Bacteriuria

Pyuria (WBC count more than 10/mm3)

Nitrite-positive urine (with nitrite reducers)

Leukocyte esterase-positive urine

 22 Urine collection
Three acceptable methods:

 Midstream clean-catch method:

 20 to 30 mL of urine is voided and discarded, the next part of the

urine flow is collected (refrigerated as soon as possible).

 preferred method for the routine collection of urine for culture

 Catheterization:

 for patients who are uncooperative or who are unable to void urine)

 1% to 2% procedure associated infection

 Supra-pubic bladder aspiration (newborn, critically ill)

 23
Cont.
Microscopic examination (Pyuria, Hematuria, and
Proteinuria)

 Pyuria:

 WBC count of greater than 10 WBC/mm3 of urine

 is non specific (only tell inflammation)

 Sterile pyuria:

associated with urinary tuberculosis; chlamydial; fungal

urinary infections
24 Cont.
 Hematuria:

Prenal calculi

PTumors

Pglomerulonephritis

Proteinuria

 is found commonly in the presence of

infection
 25 Chemistry

 The nitrite test can be used to detect the presence of

nitrate-reducing bacteria in the urine (e.g, E. coli).

False-positive tests are uncommon

False-negative tests common in presence of gram-

positive organisms or P. aeruginosa that don’t reduce
nitrate
26
Cont.
 The leukocyte esterase test

is a rapid dipstick test to detect pyuria

Found in neutrophil granules; indicate presence of

WBCs

sensitive and highly specific test for detecting more

than 10 WBC/mm3
 27 Cont.
 Leukocyte esterase test plus the nitrite test:

 the reported positive predictive value and

specificity is 79% and 82%, respectively,

 For outpatient evaluation of uncomplicated UTIs

 Urine culture: Gold standard test

 28 Culture
 Quantitative method of urine culture

Urine in the bladder is normally sterile

Patients with infection has >105 bacteria/mL of urine.

 One-third of women with symptomatic infection: may

have <105 bacteria/mL.

 Major issue:

patients with UTI, Symptomatic or asymptomatic, also

may have <105 bacteria/mL of urine
 29
Treatment
Goal of therapy

to eradicate the invading organism

to prevent or to treat systemic consequences

to prevent the recurrence of infection,

minimize unnecessary exposure to non-

causative organisms (avoid resistance)
 30 Treatment
Non pharmacologic treatment

 Fluid hydration……rapid dilution; forced removal

 Intake of large volumes of cranberry juice in patient with

recurrent UTIs (prevent adhesion)

 Lactobacillus probiotics (lower vaginal pH so reduce E.coli

colonization)

 Topical estrogen replacement for postmenopausal women

(reduce pH)
 31
Treatment
Pharmacologic treatment

 Initial selection of an antimicrobial agent depends on :

The severity of the presenting signs and symptoms,

The site of infection

whether the infection is determined to be uncomplicated

or complicated

antibiotic susceptibility,

side-effect potential and cost of therapy

 32
Treatment

 Ideally, the antimicrobial agent chosen should be

well tolerated,

well absorbed,

achieve high urinary concentrations, and

have a narrow spectrum of activity

33
Cont.
 Treatment is based on type of infection:

acute uncomplicated cystitis,

symptomatic abacteriuria,

asymptomatic bacteriuria,

complicated UTIs, or

recurrent infections,
 34 Treatment

Acute Uncomplicated Cystitis

 occur in women of childbearing age and often associated

with sexual activity

 urine culture: is not normally required due to the causative

mo and their susceptibility are known
35 Cont.

First line treatment

 Nitrofurantoin 100 mg bid × 5 days

 Cotrimoxazole 1 DS tablet bid × 3 days

 Fosfomycin trometamol 3g single dose

 36 Treatment
 fluoroquinolones reserved for patients with suspected
or possible pyelonephritis (due to the collateral damage
risk)

 Amoxicillin or ampicillin should not be used due to

the high incidence of resistant E. coli.

Alternative

 Amoxicillin/-clavulanate, cefdinir, cefaclor, or

cefpodoxime proxetil for 3 to 7 days
 37 Treatment

Symptomatic Abacteriuria

 etiology : E. coli, Staphylococcus spp., or Chlamydia

trachomatis.

 Chlamydial treatment should consist of 1 g azithromycin

or doxycycline 100 mg twice daily for 7 days.

Asymptomatic Bacteriuria

 Most of the patients are elderly and female

 In non-pregnant females, therapy is controversial;

 38 Treatment
Complicated Urinary Tract Infections

Acute Pyelonephritis

patients with infection-related vomiting, decreased

appetite, and dehydration need to be admitted

Gram stain and culture are important to ensure

antimicrobial coverage
39 Cont.

 Outpatient

Ciprofloxacin 500 mg × 7-10 days

Levofloxacin 250mg/d × 10 days

Cotrimoxazole (if susceptible) 1 DS tablet BID× 14 days

Amoxicillin–clavulanate 500mg × 14 days (G+ve

bacteria)
 40 Treatment
Inpatient treatment

 IV fluoroquinolone, Ampicillin with aminoglycoside

 ampicillin–sulbactam, ticarcillin–clavulanate, or
piperacillin–tazobactam

 Carbapenems or IV trimethoprim sulfamethoxazole

 N:B If the patient has been hospitalized within the past 6 months
or has a urinary catheter consider P.aurginosa , enterococus and
other resistant microorganisms
 41 Treatment
Urinary Tract Infections in Males

 most common causes are instrumentation of the UT,

catheterization, and renal and urinary stones

 uncomplicated infections are rare, but they may occur in

young males due to

homosexual activity, non-circumcision, and having sex

with bacteria colonized partners
 42 Cont.
 prolonged treatment is required (10-14days)

 since the cause is not predictable culture should be

obtained before treatment

 cotrimoxazole or the quinolone should be considered

a c h i e v e h i g h r e n a l t i s s u e , u r i n e , a n d p r o s t a t i c
concentrations
43 Cont.
 44 Treatment

Urinary Tract Infections in Pregnancy

 About 4% to 7% of pregnant patients develop
asymptomatic bacteriuria; of these, 20% to 40% will develop
acute pyelonephritis

 If untreated, ASB may cause prematurity, low birth weight,

and stillbirth
45 Cont.

 Seven-day course of amoxicillin, amoxicillin–

clavulanate, or cephalexin is effective in 70% to 80% of
patients

 sulfonamides should not be administered during the 3rd

trimester due to possible development of kernicterus &
hyperbilirubinemia

 Tetracyclines and fluoroquinolones should be avoided

46 Recurrent Infections
 Reinfections ………….accounts up to….. 80%
 Two groups:
 Those with less than 2-3 episodes per year
 those who develop more frequent infections (>
3episodes).
 Risk Factors…………. Patient counseling
 sexual intercourse ……… void after
 diaphragm or spermicide use for birth control.
 Nylon panties; back to front wiping
 47 Cont.
Treatment
 Short-course better………..
 Trimethoprim-sulfamethoxazole (one-half of a single-
strength tablet), trimethoprim (100 mg daily)
 a fluoroquinolone (levofloxacin 500 mg daily)
 nitrofurantoin (50 or 100 mg daily)
 Duration…..6 months, urine cultures to be followed
monthly
48

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