UTIs Flashcards
Is bacteriuria pathological?
Bacteriuria = presence of bacteria in urine
Urethra is not sterile - as urine passes through organisms picked up
Bacteriuria is only treated in pregnancy and if symptomatic
What % women will experience symptomatic UTI in their lifetime?
40-50%
Which organism predominantly causes UTIs?
E coli (95%) - specifically O1, O2, O4, O6, O7, O8, O75, O150 - have special p fimbriae to cling on
Organism associated with UTI in young women
Staphylococcus saprophyticus
What are the three main defences against UTI?
3 Us - urine (low osmolality, low pH), urine flow and micturition, urinary tract mucosa (bactericidal, cytokines)
3 organisms associated with UTI in complicated UTI
Complicated UTI = urinary tract structural/functional abnormality (e.g. catheter, stent, calculi)
P mirabalis, K aerogenes, E faecalis
Organism associated with in-dwelling catheters and prosthetics
S epidermidis
What are the mechanisms of UTI?
Most commonly ascending UTI (bacteria colonise urethra - ascend up urinary tract - multiply in bladder - can pass to ureters and kidneys)
Haematogenous spread from bacteraemia can occur - beware if S aureus in urine
Note: Bad MSU can be false positive
What factors can make ascending UTI more likely?
Anything interfering with 3 Us - commonly obstruction stopping urine flow
- Renal obstruction
- Neurogenic malfunction
- Vesicoureteral reflux (residual pool of urine in bladder after voiding can reflux up ureters)
- Females - bacteria colonising warm, moist vulval area and short urinary tract
How does UTI present in different age groups?
Neonates, children <2: Non-specific (failure to thrive, vomiting, fever)
Children >2: More localised (frequency, accidents, dysuria)
Adult: Localised, dependent on upper or lower UTI
- Lower: LUTS (FUD)
- Upper: LUTS (FUD) + fever, flank pain
Old-age: Asymptomatic, confusion, ?non-specific
> 3 typical symptoms of UTI - Ix and Rx?
- Check for vaginal discharge to rule out STI
2. No urine dipstick needed - give empirical Abx treatment
<2 typical symptoms of UTI - Ix and Rx?
- Check for vaginal discharge to rule out STI
- Obtain urine sample and check if cloudy - if not cloudy unlikely UTI - DON’T TREAT
- Urine dipstick - check nitrites + leucocytes (+ protein)
- a) Positive nitrites (+/- protein, leucocytes) = Probable UTI - TREAT
b) Negative nitrite, protein and leucocyte - Unlikely UTI - DO NOT TREAT
c) Negative nitrite, positive leucocyte - Treat if severe symptoms, send for MC+S
d) Negative nitrite and leucocyte, positive protein - DO NOT TREAT
On urine dipstick, which parameter has the best positive predictive value?
Nitrites
MC+S is not routine - when should it be used?
- Urine dipstick negative for nitrites but positive leucocytes
- Pregnancy
- Suspected pyelonephritis
- Complications (men, catheter, structural abnormalities)
- Abx resistance (if UTI not responding)
How is MC+S conducted?
M (microscopy - WCC triage)
C (culture to determine organism - chromogenic agar = pink E coli - takes 24h)
S (sensitivity - zones of inhibition analysed - further 24h)
