urinary tract infections Flashcards
describe the epidemiology of a UTI? 2
- 1-3% of all GP consultations
- Significant cause of morbidity in females of all ages, infant boys and older men
what are the consequences of a UTI? 6
- Societal and individual costs- health care costs, time missed from work
- Frequent recurrences
- Uncontrolled infection- sepsis
- Renal damage in young children
- Preterm birth
- Recurrent causes of AB contribute to antimicrobial resistance and risk of C. difficile infection
describe the classifications of UTI? 5
- Uncomplicated lower UTI:
- Cystitis
- Urethritis, prostatitis, epididymo-orchitis
- .
- Uncomplicated upper UTI:
- Acute pyelonephritis
what is an uncomplicated UTI?
there is no anatomical or neurological abnormalities of the urinary tract
what is UPEC?
uropathogenic Escherichia coli
describe the host factors of a lower UTI? 7
- Obstruction (prostatic hypertrophy, urethral valves or stricture)
- Poor bladder emptying (neuropathic (MS, spinal cord injury), bladder diverticula, pelvic floor disorders)
- Catheterisation/ instrumentation
- Vasico-enteric fistula
- Sex (vaginal or anal)
- Diabetes
- Genetics= non secretors of ABH blood group antigens, especially in premenopausal women, and variable expression of the CXCR1 receptor, involved in neutrophil action
describe the host factors of an upper UTI? 3
- Same as lower
- Vesico- ureteric reflux
- Obstruction (calculus, stricture)
describe the pathogenesis of a UTI? 10
- Contamination of the periurethral area with a uropathogen from the gut
- Colonisation of the urethra and migration to the bladder
- Colonisation and invasion of the bladder, mediated by pili and adhesins
- Neutrophil infiltration
- Bacterial multiplication and immune system subversion
- Biofilm formation
- Epithelial damage by bacterial toxins
- Colonisation of the kidneys
- Host tissue damage by bacterial toxins
- Bacteraemia
what does bacterial virulence depend on? 3
- Adherence
- Invasion
- Evasion
describe adherence in a UTI? 3
- In the bladder, uropathogenic Escherichia coli (UPEC) expression of type 1 pili is essential for the colonisation, invasion and persistence
- P-pili confer tropism to the kidney
- UPEC are highly adhesive so are proficient in retrograde ureteral ascent
describe the clinical diagnosis of a UTI? 4
- Clinical symptoms
- Urine dipstick testing at point of care- main use to determine treatment if symptoms are vague- not diagnostic on their own, not useful if >65 of catheterised
- Urine culture- don’t need to do this in simple 1st episode cystitis in a non-pregnant adult female
- Look for nitrates, leucocytes and RBC
what is cystitis? 5
ladder and urethral symptoms
- Overlap with urethritis
- Dysuria, frequency, urgency, suprapubic pain, nocturia
- Cloudy urine, visible blood
- Children, elderly and catheterised can be non-specific, such as delirium, lethargy
what is pyelonephritis? 5
- Fever, rigors, loin pain
- Renal angle tenderness
- Often lower UTI symptoms in addition
- If pain radiation to the groin- stone?
- Risk of bacteraemia
describe the laboratory diagnosis of a UTI? 5
- Send to lab for culture if- pregnant, children, men, elderly, recurrence, failed treatment, renal impairment
- Principles of a urine culture- urine in the bladder should be sterile in the absence of a UTI
- It can be contaminated by bacteria colonising the distal urethra of hands/genital contamination
- 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 the growth of any contaminants by rapid transport to the land (>4h) and/or boric acid preservative and/or refrigerate
describe urine specimens? 3
- Midstream urine
- Suprapubic aspirate
- Catheter urine (acute, intermittent self-catheterisation, indwelling)
what helps to maintain the microbiological quality of the urine? 3
- Boric acid
- Prevents cell degradation and overgrowth of organisms that can occur if the sample is not analysed within 4 hours of collection
- Can cause a false negative culture if urine is not filled to the mark on the specimen bottle and can affect urine dipstick tests.
describe the microscopy of the UTI? 3
- White cells represent inflammation in the urinary tract
- Automated urine analysers in the lab scan for red cells, white cells and organisms
- Discard without culturing if the scan is negative. (Unless immunosuppressed or neonate)
describe a culture and antibiotic sensitivity in a UTI?
- Quantitative
- > 10^5 per ml is significant bacteriuria- probably not contaminants
- Mixed growth may show contamination over true mixed infection
describe what you should consider for the antibiotic treatment of a UTI? 5
- Target organisms
- Route of administration
- Target site
- Side effects
- Resistance
how do we know about antimicrobial resistance rates? 3
% of hospital microbiology labs in England report routine antimicrobial susceptibility testing results with patient demographic information to the PHE national laboratory surveillance system
- This helps inform antibiotic prescribing guidance
- This is biased as it is only based on isolates sent for diagnostic testing
how can we prevent a UTI? 3
- Correct any underlying host causes (uncontrolled DM)
- Antibiotic prophylaxis (temporary, between 6m and 2y)
- Behavioural changes, high fluid intake, void after sex, double void
describe catheter associated UTI? 4
- Bacteria colonise in the catheter and bladder
- Removal of catheter will clear bacteria in most cases
- Usually asymptomatic, but some will develop TUI, bacteraemia, sepsis and die
- 69% of events are avoidable
how do we prevent catheter associated UTIs? 8
- Use only for a good reason:
- 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
- Consider alternatives
how do we diagnose catheter associated UTI? 3
- Do not use dipstick testing
- Take a catheter sample of urine when diagnosis has been made to guide antimicrobial treatment
- Must involve assessing for clinical signs and symptoms compatible with a CAUTI
what is asymptomatic bacteriuria? 3
- Best left untreated unless pregnant
- Extremely uncommon in elderly patients as organisms often lack virulence factors
- Treatment is not benign- adverse effects, financial cost, development of resistant strains
what is relapse in a UTI?
the same uropathogen causes UTI symptoms within 2 weeks of completing appropriate AB treatment
what is recurrence in a UTI?
at least 2 culture-proven episodes in 6 months, or at least 3 in 1 year (different uropathogen or after 2 weeks)
