Download Urinary Tract Infection

Pathophysiology of urinary tract infection
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Ascending route of infection is the
most common.
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Hospital infection associated with
lower urinary tract instrumentation
(catheterization, cystoscopy).
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Once in the bladder uropathogens
multiply, then pass up the ureters to
the renal pelvis and parenchyma
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Source of uropathogens: enteric
bacteria mainly
Urinary tract infection more common in
women than men
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Short female urethra.
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Close proximity to perianal areas.
• Men also have an antibacterial
substance in their prostate gland that
reduces their risk.
Pathophysiology of urinary tract infection
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Cystitis: (lower urinary tract infection)
Pyelonephritis: infection of the kidney
with acute suppurative inflammation of the
 pelvis,
 medullary and cortical tubules,
 corticomedullary intersititum
Urosepsis: bacteremia due to pyelonephritis
Papillary necrosis
Sloughing of necrotic pyramids
Perinephric abscess
Risk factors in complicated urinary tract
infection
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Indwelling catheters
Urinary calculi
Neurogenic bladder
Prostatic enlargement
Uterine prolapse
Urologic instrumentation or
surgery
Renal transplantation
Diabetes mellitus
Common uropathogens
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Escherichia coli
Other Enterobacteriaceae
(Klebsiella, Enterobacter,
Proteus, Citrobacter)
Pseudomonas aeruginosa
Enterococcus
Staphylococcus saprophyticus
Staphylococcus aureus
• Associated with
staphylococcemia
Streptococcus agalactiae
(group B)
• Denotes vaginal
colonization in
pregnant women
Candida
Uncommon uropathogens
• Corynebacterium urealyticum
• Haemophilus influenzae and H.
parainfluenzae
• Blastomyces dermatitidis
• Neisseria gonorrhaeae
• Mycobacterium tuberculosis
Notes
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Adult urine volume = 600 – 2500 ml /24hr.
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Oligouria: marked decrease in urine flow < 400 ml/24hr.
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Polyuria: Marked increase in urine flow > 2500 ml/24hr.
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Anuria: less than 100 ml/24hr.
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Nocturia: excessive urination during night.
• Aim of the test
 An etiological diagnosis of bacterial urinary tract
infection by quantitative
 Cultivation of the urine with identification and
susceptibility test of the isolated bacteria(s).
• Criteria of specimen rejection
 Un-refrigerated specimen older than 2 hours may be
subject to overgrowth
 unlabeled specimen; mislabeled specimen;
 Specimen in expired transport container
Types of urine specimens
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First-voided morning urine optimal (generally bacteria have been proliferating
in bladder urine for several hours)
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Midstream urine specimens (initially voided urine contains urethral
commensals)
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Indwelling catheters (freshly placed, urine aspirated by needle inserted into
catheter) (Foley catheter tips not acceptable)
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Straight catheter specimens
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Suprapubic aspirates (infants or children, recovery of anaerobes)
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Cystoscopic collection of urine
Specimen collection
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Male:
1.
2.
3.
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If not circumcised, draw back the foreskin.
Begin to urinate, but pass the first portion into the toilet.
Collect the mid-portion of urine into the container, and pass the excess into
the toilet.
Female:
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2.
3.
Squat over the toilet and separate the labia with one hand.
Void the first portion of urine into the toilet.
Collect the mid-portion of urine into the container and pass the excess into
the toilet.
Collection of urine specimens
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Urine collected in sterile
specimen container must be
processed within hours, or
refrigerated and processed
within 24 hours
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Urine collected in sterile
specimen container with
borate preservative should
be processed within 24
hours (no refrigeration
required)
Catheterized urine
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Cleanse periurethral area with soap and water
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Insert catheter into bladder
 Discard initial urine
 Collect specimen in sterile cup
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Chronic indwelling Foley catheter
 Clamp tubing below junction (or port)
 Disinfect with alcohol
 Insert needle (on syringe) through port or catheter wall and aspirate.
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DO NOT recontamination
Suprapubic aspiration
Inoculation of urine
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Inoculation of urine for quantitative culture (colony
forming units→ CFU’s) performed with a calibrated
0.001 mL(1µL) and 0.01 mL (10µL) plastic or wire
loop
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Nutrient agar or sheep blood agar utilized for
quantitative urine culture
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With 0.001 ml loop, 1 colony on SBA equivalent to
1,000 CFU’s per mL of urine
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With 0.01 ml loop, 1 colony on SBA equivalent to 100
CFU’s per mL of urine
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MacConkey agar utilized as selective differential agar
for gram-negative bacteria
Count plate
Interpretation: Clean Voided Specimen
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Normal: <10,000 organisms per ml.
Organisms >10,000 per ml needs repeat
urine culture?
Urinary Tract Infection
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Boys
• Organisms >10,000 per ml
suggests UTI likely
 Girls
• Organisms >100,000 per ml
suggests UTI
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Three specimens: 95%
probability of UTI
Two specimens: 90%
probability of UTI
One specimen: 80%
probability of UTI
Post specimen processing
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Interfering factors:
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Patient on antibiotic therapy.
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Improper sample collection.
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Result reporting:
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Report wet mount as an initial report.
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Report the isolated pathogen and its sensitivity
pattern as a final report.
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Turn around time:
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Wet mount results should be available 1 hour
after specimen receipt.
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culture will be reported out 1-2 days after the
receipt of the specimen.
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Isolation of a possible pathogen can be
expected after 2-3 days
Negative