UTIs Flashcards
(28 cards)
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)
What MC+S findings on microscopy support UTI?
- > 10^4 colony forming units with urinary symptoms (>10^3 if E coli or S saprophyticus)
- White cell triage - no culture if <10^4 white cells
Sterile pyuria
Sterile pyuria = pus in urine but no organisms cultured
Consider non-culturable organisms e.g. TB, Chlamydia
Why is it important to inform the lab if a patient is immunocompromised or pregnant?
White cell triage:
- Pregnant - bacteriuria important regardless of WCC
- Immunocompromised - low WCC may prevent culture from being performed
Why is chromogenic agar used for culture in MC+S for UTI?
Urine is not sterile so non-causative organisms will also show up
Uses colour to indicate organisms present (e.g. E coli is pink)
What does lots of squamous epithelial cells on microscopy indicate?
Bad MSU - only urethra lined by squamous, rest is columnar
Uncomplicated lower UTI Tx
Cefalexin / trimethoprim / Nitrofurantoin
3 days if non-pregnant/breast-feeding female
7 days if male or pregnant/breast-feeding female
Gram negative rod-shaped anaerobe
E coli
Upper UTI Tx
IV co-amoxiclav + IV gentamicin for 1-2 days - oral switch in discussion with micro - treat for 14 days
If elderly, frail, risk of C difficile - IV gentamicin only (avoid co-amoxiclav)
What is the treatment for UTI if a catheter is present?
IV gentamicin prior to catheter removal - only follow with treatment if systemically unwell
