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CPR93: Urinary tract infection

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UTI prevalence
Adult women (25% by 30y.o.) > Children (1-2%) > Neonate (M1.5%, F0.1%) > Adult men (rare until obstruction from BPH)
UTI significance
Elderly 10% & 30-40% of all hospital acquired infections (HAI); often associated with use of catheters
UTI potential consequences
bacteremia, chronic renal failure, urinary stones
UTI Economic impact
work loss, prolonged hospital stay
Host defenses of urinary tract
Flushing effect of urine > Humoral immunity & Cell mediated immunity
Host-microbe interaction
Adherence -> colonization (host factor & bacterial factors)-> infection (Entry, Spread & Multiplication, Damage)
Host-microbe interaction: ENTRY
Ascent from urethra (Most by enteric or skin bacteria) or even zoonosis of food
UTI pathogens
Escherichia coli, Proteus mirabilis, Staphylococcus saprophyticus, enterococcus
E coli in UTI
E. coli associated with UTI is often called uropathogenic E. coli (UPEC) or extraintestinal pathogenic E. coli (ExPEC)
Iron acquisition
Usually needed for replication e.g. UPEC, Kleb P, Proteus, Psuedo A
UPEC/ ExPEC virulence factors
Flagella, Type I &P Fimbriae, G-ve(Lipopolysaccharide, capsular polysaccharide), Toxins(Hemolysin, aerobactin, protease)
ENTRY host factors
Length of urethra, Mechanical factor (sex, trauma, contraceptive diaphragm, catheter), Genetic factor (e.g. density of bacterial receptors) – not well defined, Hormonal effect on mucosa, Underlying disease
Host-microbe interaction: SPREAD
Bladder -> Kidney -> Blood
SPREAD mechanism
Reflux (incompetent ureterovesical valves), Poor emptying (neurogenic bladder), Dilatation & ↓peristalsis of ureter (pregnancy), Nidus for persistence (urinary catheter), Obstruction (stones), Immune incompetence (DM)
Host-microbe interaction: DAMAGE
Polysaccharide: inhibit phagocytosis, Lipopolysaccharide: inflammation, Hemolysin of E. coli: tissue damage, Urease: stone formation
Urease problem
Urea (with urease) -> NH3 -> ↑Urine pH -> Precipitation
Uncomplicated UTI (cystitis/pyelonephritis)
refers to infection in a structurally and neurologically normal urinary tract -> affect otherwise healthy individuals
Uncomplicated UTI pathogens
UPEC > K. pneumoniae/ S. saprophyticus > Enterococcus spp.
Complicated UTI pathogens
UPEC > Enterococcus spp. > K. pneumoniae >Candida spp.
Syndrome of UTI
Acute pyelonephritis, Perinephric abscess, Cystitis, Asymptomatic bacteriuria & Prostatitis
Acute pyelonephritis
high fever, loin pain
Perinephric abscess
in patient with underlying disease such as DM.
frequency, dysuria, suprapubic discomfort
Asymptomatic bacteriuria
A laboratory diagnosis / No symptoms
Acute ‐ fever, perineal pain, Chronic ‐ non‐specific, difficult to diagnose
Recurrent infection
Relapse (same bacterial strain, a consequence of bacterial persistence
Microbiological diagnosis
Pyuria(>10WBC per high power fieldß) ,significant bacterium
Nitrite detection in urinalysis
Some bacteria including the lactose positive Enterobactericeae, Staphylococcus, Proteus and Psuedomonas are able to reduce nitrate in urine to nitrite
Nitrite detection in urinalysis color
Nitrite react with substrates in strip to produce a pink color
Nitrite detection in urinalysis limitation
Negative test may not reliable ruled out UTI because 1. Some bacteria (e.g. enterococcus) do not have the ENZYME for reducing nitrate to nitrite 2. Urine may not be retained in the bladder for LONG enough for bacteria to reduce nitrate (e.g. frequent voiding)
Esterase in urinalysis
Leukocyte esterase is used as an indicator of leukocyte in urine.
Esterase in urinalysis color
leukocyte esterase react with substrates in strip to produce a purple color
Esterase in urinalysis limitation
Some drugs (e.g. cephalexin, high glucose level) may interfere with chemical reaction -> FALSE negative results, OR Positive result may occur from CONTAMINATAION of specimens by vaginal discharge
Significant bacteriuria methods
Quantitation or semi-quantitative culture (differentiate contamination or genuine bacteriuria) by standard loop, paper strip, dip slide
Culture medium
CLED agar; inhibit swarming, colony morphology
Interpretation of results
Above 10^3 below 10^5 /ml need clinical interpretation
MSU Significant bacteriuria
≥10^5 cfu per ml (2 samples if no symptoms)
Clean-catch urine (baby) Significant bacteriuria
≥10^5 cfu per ml (caution required)
Pediatric urine bag Significant bacteriuria
≥10^5 cfu per ml (caution required)
CSU (indwelling urine catheter) Significant bacteriuria
≥10^5 cfu per ml
Suprapubic tap urine Significant bacteriuria
Any growth
Interpretation caution(1)
Some symptomatic patients with UTI do not have counts ≥10^5 cfu/ml e.g. Women with uncomplicated cystitis & Male patients
Interpretation caution(2)
If pure growth (especially E. coli) – lower colony counts may still be clinically significant
Specimen collection
avoid cleaning with antiseptic, which may contaminate urine (false negative). & whip in backward direction
False positive
heavy colonization of vagina O delay transport >2h
Asymptomatic bacteriuria
Common in elderly, debilitated. No urine culture if no UTI symptoms, no significant consequence, usually no Rx needed
Asymptomatic bacteriuria that needs Rx
Pregnant women (20-30% risk of progression to acute pyelonephritis if not treated), Before urological operation (e.g. transurethral resection of prostate), OR Children (age <5 years), when associated with vesico-ureteric reflux
Recurrent UTI
Recurrent episodes afflict 1 in 10 women at some time in their life, Most do NOT have structural abnormality
Recurrent UTI characteristics
Behavioral factors, Either unusually receptive uroepithelial cells; OR colonization by ‘stick strains’ of E. coli
Urological evaluation in young women
Yield of significant lesion <1%, Indicated if recurrent plus Haematuria between infections/ Pyelonephritis/ Obstructive symptoms/ Urea-splitting bacteria/ Urinary calculi/ Severe Diabetes
Acute bacterial prostatitis(ABP) RF
Unprotected anal intercourse, Indwelling urinary catheter use, Prostate biopsy
ABP Clinical presentation
Dysuria, frequency, High fever common (patient often very ill), Urinary retention common (obstruction from acute edema of prostate), Per rectal examination -> very tender prostate
ABP Urine culture
Yield pathogen (often E. coli) at ≥10^5 cfu/ml
Chronic bacterial prostatitis
Relapsing UTI by the same organism, Positive 4 or 2 –glass test
Chronic bacterial prostatitis Accepted pathogens
E. coli (up to 70%), Other Enterobacteriaceae, Pseudomonas aeruginosa, Enterococci
Chronic bacterial prostatitis Doubtful candidates
S. epidermidis, Chlamydia trachomatis, Mycoplasma genitalium, Ureaplasma urealyticus
Chronic bacterial prostatitis Associated conditions
Retrograde spread of bacteria into prostatic ducts, Dysfunctional voiding, Previous instrumentation
4 glasses test
1st voided 10 ml (VB1)-> 200 ml later = MSU (VB2) -> prostate massage -> E.P.S -> 1st voided after massage (VB3)
4 glasses test problem
Difficult to perform, Limited sensitivity for Gram-pos
4 glasses test
VB3 > VB2 1 Log = Dx
2 glasses test
1st void 10 ml VS semen (1 Log higher = Dx, Repeat if ejaculate yield Gram positive bacteria)
6-12 weeks antibiotics