UTIs Flashcards
What are the most common organisms implicated in UTIs?
Gram-ve rods e.g. coliforms (E.coli - ~75% of UTIs)
Other enterobacteria e.g. Enterococcus faecalis, Proteus spp., Klebsiella
Hospital: Pseudomonas aeruginosa (catheterisation: Staph. epidermidis, Enterococcus faecalis)
(Staph. saprophyticus, S. aureus)
At what ages are UTIs most common?
Infancy
Pre-school (hygiene)
“Honeymoon cystitis”
Pyelitis of pregnancy
Prostatism
What are some host factors implicated in UTIs?
Shorter urethra in females
Obstruction (prevents clearance of microbes via outflow of urine) e.g. prostatic hypertrophy, calculi, tumours, pregnancy (pressure on bladder/uterine prolapse)
Neurological problems e.g. preventing complete emptying -> residual urine stagnates and microbes multiply
Ureteric reflux occurs in children (valves preventing backflow of urine are absent/dysfunctional) which causes ascending bladder infections
What are some bacterial factors implicated in UTIs?
Fimbriae attach to host epithelium
K antigen permits production of polysaccharide capsule
Urease breaks down urea, creating a favourable environment for bacterial growth (metabolism + ammonia cloud)
Haemolysis breaks down host membranes and causes renal damage
What are some symptoms/clinical syndromes associated with UTIs?
- asymptomatic (can progress to symptomatic e.g. in pregnancy can lead to premature, low birth weight babies)
- frequency of urination +/-dysuria (burning/stinging pain on passing urine) -> lower UTI (cystitis)
- urgency
- fever
- loin pain (referred as one-sided back/groin)
- supra-pubic pain
- acute pyelonephritis (pus in kidneys) -> upper UTI
- chronic nephritis
- septicaemia +/- shock
note: children: non-specific symptoms e.g. drawing legs up (abdominal pain), elderly: confused
Contrast uncomplicated and complicated UTIs.
UNCOMPLICATED:
Healthy women of child-bearing age w. no associated disease
Infection indicated by urine dipstick (no culture required)
3 day course of trimethoprim/nitrofurantoin
COMPLICATED:
Pregnancy/male/paediatric/sickle-cell anaemia/diabetes/suspected pyelonephritis/catheterisation/surgery/other complications inc. calculi, obstruction, polycystic kidneys, reflux of urine
Infection indicated by urine dipstick + urine culture
5-7 day course of trimethoprim/nitrofurantoin/cephalexin (50% of isolates resistant to amoxicillin)
Follow-up culture in pregnancy & paediatrics
How can urine samples be collected? What measures are taken to obtain an accurate result?
Midstream collection (urine sampled is from bladder and not contaminated by genital bacteria)
Collection bag attached to young children who cannot urinate on command (!risk of contamination by skin flora)
Catheter sample
Supra-pubic aspiration (only is impossible to obtain sample otherwise)
note: no antiseptic needed (may give false+ve); transported at 4 degrees celsius + boric acid (prevents contamination & multiplication to obtain an accurate picture of type & no. of bacteria)
How can urine be screened by near patient testing?
TURBIDITY = colour & clarity of urine (can be used to exclude UTIs)
DIPSTICK =
- leukocyte esterase: indicates inflammation (low specificity)
- nitrite: bacteria can metabolise nitrates to nitrites (very reactive - high risk of false+ve result)
- haematuria
- proteinuria
note: N+/L- or N-/L+ does not indicate UTI alone (send for culture) BUT presence of turbidity or N+/L+ indicates a UTI
In what situations is urine screening helpful and unhelpful?
Helpful (to exclude UTI):
- children > 3yrs
- men with mild/non-specific symptoms
- elderly/institutionalised women
Unhelpful:
- acute uncomplicated UTI in women
- men with typical/severe symptoms
- catheterised patients (only if systemically unwell, even with +ve dipstick)
- older patients without features of infection (due to reduced immune function; not associated with increased morbidity and mortality, therefore not routinely dipsticked)
BECAUSE treatment is not required (prevents antibiotic resistance increasing) OR because the treatment plan will not change because of screening result
When is urine microscopy indicated?
Kidney disease (loin pain, nephritis, hypertension, toxaema, renal colic, haematuria, renal TB, RBC casts)
Suspected endocarditis
Children < 6yrs
Schistosomiasis
Suprapubic aspirates
Pregnancy/urological surgery (with asymptomatic bacteruria)
What information does urine culture provide?
No. of colony forming units (>10^5 cfu/ml indicates bacteriuria/contamination - not well studied in cystitis, men, and children)
Differentiates lactose-fermenting bacteria from non-lactose-fermenting bacteria (reduced pH causes colour change)
What are some important differentials for UTI in symptomatic adult women?
Urethral syndrome (low microbe count/fastidious bacteria)
Vaginal infection/inflammation
Urethritis (STI)
Mechanical/physical/chemical cause
When is imaging indicated in UTI?
All children - to check for valve defects
Males: posterior urethral valves
Females: vesico-ureteric reflux
Septic patients (determine renal involvement)
What is sterile pyuria, and what can cause it?
Sterile pyuria = WBCs in urine without infection
- antibiotics
- urethritis
- vaginal infection/inflammation
- chemical inflammation
- TB
- appendicitis
- ?fastidious organisms
What is the general treatment for UTIs?
Increased fluid intake (flushing may help clear bacteria)
Address underlying disorders
3day/7day course of antibiotics (uncomplicated v.s. complicated)
- trimethoprim/nitrofurantoin/cephalexin
