Urinary tract infections Flashcards
Consequences
Societal and individual costs- health care costs, 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 CDI
Classification
Uncomplicated ‘upper’ UTI
- acute pyelonephritis
Uncomplicated ‘lower’ UTI
- cystitis
- urethritis, prostatitis, epididymo-orchitis
Uncomplication
- no anatomical or neurological abnormalities of the urinary tract
Aetiology
Uropathogenic escherichia coli
Host factors: lower UTI
Catherisation/ instrumentation
Diabetes
Obstruction (prostatic hypertrophy, urethral valves or stricture)
Poor bladder emptying (neuropathic, bladder diverticula)
Sexual intercourse (female: vaginal or anal; male- insertive anal)
Vesico- enteric fistula
Host factors: upper UTI
May follow on from lower UTI
Vesico- ureteric reflux
Obstruction (e.g. calculus, stricture)
Pathogenesis
- Contamination of the periurethral area with a uropathogen from the gut
- Colonisation of the urethra and migration to the bladder
- Clonisation and invasion of the bladder, mediated by pili and adhesins
- Neutrophil infiltration
- Bacterial multiplication and immune system subversion
- Biofiilm formation
- Epithelial damage by bacterial toxins and proteases
- Ascension to the kidneys
- Colonisation of the kidneys
- Host tissue damage by bacterial toxins
- Bacteremia
Adherence
In the bladder UPEC expression of type 1 pili is essential for colonisation, invasion and persistence
P-pilli confer tropism to the kidney
UPEC are highly adhesive so are proficient in retrograde ureteral ascent
Invasion
Type 1 pilus binds to host cell
Induces actin rearrangement within the host cell and causes uptake of the bacteria
Inside the cell, the bacteria us protected from many antibiotics and host defences
Evasion
UPEC escapes into the cytoplasm where it multiplies up into intracellular bacterial communities
Hemolysin A forms pores in the host cell which promotes host cell lysis, releasing iron and other nutrients
Diagnosis
Can be clinical diagnosis
Dipstick test at point of care
Main use is to determine treatment if symptoms vague
Look for nitrites +/- leukocytes
- if negative, excludes UTI
- if positive with symptoms suggestive of cystitis, treat
Don’t need to send for culture in simple cystitis in non-pregnant adult female
Who gets a MSU
Pregnant
Children and men
Pyelonephritis
Recurrence
Failed treatment
Abnormal urinary tract
Renal impairment
Microscopy
Automated urine analysers in lab
Scan for red cells, white cells and organisms
Discard without culturing if scan negative
Culture and antibiotic sensitivity
Quantitative
> 10^5 organisms per ml is ‘significant bacteriuria’ (in MSU only)
UTI can be <10^5
Prevention of UTI
Correct any underlying host causes
Antibiotic prophylaxis (temporary between 6m adn 2y)
Behavioral changes e.g. high fluid intake (cranberry juice not recommended any more), void after sex, double void
Catheter associated UTI
Bacteria colonise the catheter and bladder at a rate of 3-5% people/ catheter day
Removal of catheter will clear bacteria in more cases
Usually asymptomatic, ut some will develop UTI, and bacteremia, sepsis and death may result
21% patients with an E.coli blood stream infected had UC inserted/ removed/ manipulated in prior 7 days
