Urinary Tract Infections Flashcards
Consequences of UTIs
Societal and individual costs – health care costs (GP, ED and hospital), time missed from work
Frequent recurrences
Uncontrolled infection / sepsis
Renal damage in young children
Preterm birth
Recurrent courses of AB contribute to antimicrobial resistance and risk of C difficile
Classification
Uncomplicated ‘lower’ UTI - cystisis, urethritis, prostatitis, epididymis-orchitis
Uncomplicated upper UTI - acute pyelonephritis - uncomplicated = no anatomical or neurological abnormalities
Risk factors
uncomplicated: female, older/younger
complicated: indwelling catheters, immunosuppression, urinary tract abnormalities, antibiotic exposure
Pathogenesis - host factors
Lower UTI: Obstruction (prostatic hypertrophy, urethral valves or stricture),
Poor bladder emptying (neuropathic (MS, spinal cord injury), bladder diverticula, pelvic floor disorders), Catheterisation/instrumentation,
Vesico-enteric fistula,
Sex (female – vaginal or anal; male – insertive anal),
Diabetes,
Genetics: non-secretors of ABH blood group antigens, esp in premenopausal women; and variable expression of the CXCR1 receptor, involved in neutrophil activation
Upper UTI: Vesico-ureteric reflux
Obstruction (calculus, stricture)
Adherence
In the bladder, uropathogenic Escherichia coli (UPEC) expression of type 1 pili is essential for colonization, invasion and persistence.
P-pili confer tropism to the kidney
UPEC are highly adhesive so are proficient in retrograde ureteral ascent
Invasion
Bind to host cell, and induces active rearrangement within host cell, and causes uptake of bacteria into host cell.
Once inside, bacteria is protected from antibiotics and host defences
Toll like receptor recognition – activates pathways to push bacteria out (exocytosis)
Evasion
UPEC evades this by escaping into cytoplasm, where it multiplies up into intracellular bacteria communities which invade more host cells, or invade transitional cells below, establishing a quiescent intracellular reservoir, and can survive there for months
UPEC survives within the bladder by secreting a number of factors to enable nutrient acquisition – haemolysin A
Clinical Diagnosis
Symptoms, urine dipstick testing, urine culture
Cystisis: bladder and urethral symptoms, overlap with urethritis, dysuria, frequency, urgency, suprapubic pain, nocturia, cloudy urine/visible blood
Pyelonephritis: fever, rigors, loin pain, renal angle tenderness, often lower UTI symptoms in addition, if pain radiation to groin - stone?, risk of bacteraemia
Diagnosis: look for nitrites, leucocytes and rbcs on dipstick
Lab Diagnosis
Pregnant, children, men, elderly, pyelonephritis, recurrence, failed treatment, abnormal urinary tract, renal impairment
A mid-stream urine (MSU) reduces the effects of urethral contamination by avoiding the initial and end stages of micturition. The initial urine flow washes away urethral colonisers
Minimise growth of contaminants by: rapid transport to lab (<4h), and/or boric acid preservative and/or refrigerate
Make urine specimens suprapubic aspirate
Culture and antibiotic sensitivity
quantitative
>105 organisms per ml is “significant bacteriuria” (in MSU only)
ie, probably not contaminants (90% specific)
UTI can be < 105 cfu/mL
Mixed growth may represent contamination
How do we know about antimicrobial resistance rates
labs report routine antimicrobial susceptibility testing (AST) results, with patient demographic information, to the PHE national laboratory surveillance system.
This is then used to inform antibiotic prescribing guidance
However this may be biased in that it is only based on isolates sent for diagnostic testing – ie not all UTIs
A key recommendation of the English Surveillance Programme for Antimicrobial Utilisation and Resistance (ESPAUR) is sentinel surveillance (information from a wider range of patients)
Prevention of UTI
Correct any underlying host causes (uncontrolled DM) Antibiotic prophylaxis (temporary, between 6m and 2y; not evidence based) Behavioural changes eg high fluid intake (cranberry juice not recommended any more), void after sex, double void.
Prevention of catheter-associated UTIs
Use only for a good reason: How to diagnose a CAUTI
- Measurement of urine output in acutely unwell
- Mx of acute retention or obstruction
- Selected surgical procedures
Aseptic insertion
Closed drainage system
Daily review of need: remove promptly when no longer indicated
Relapse vs Recurrence
Relapse = the same uropathogen causes UTI symptoms within 2 weeks of completing appropriate AB treatment
Recurrence = at least 2 culture-proven episodes in 6 months, or at least 3 in 1 year
- beyond the initial 2 weeks
- or a different uropathogen
