Urinary tract infections Flashcards
How common are UTIs?
2nd only to resp infections; 1-3% of all GP consultations.
Which groups are at risk of morbidity?
Significant cause of morbidity in females of all ages, infant boys and older men.
Who is most likely to get a UTI?
Up to 50% of women in lifetime, many recurrent (20% within 6 months), most not severe
1 to 2% of infants (boys < 3 months old 3x> girls)
Men rare until old age (prostatic enlargement)
____% elderly have asymptomatic bacteriuria
_____% of all nosocomial infections in men and women are UTIs; _______% of these develop secondary to indwelling catheters.
20% elderly have asymptomatic bacteriuria.
Forty percent of all nosocomial infections in men and women are UTIs; 80% of these develop secondary to indwelling catheters.
What are the consequences of UTI?
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 CDI (C. difficile infection)
What are the types of uncomplicated UTIs?
Uncomplicated “Lower” UTI
- Cystitis
- Urethritis, prostatitis, epididymo-orchitis
Uncomplicated “Upper” UTI
•Acute pyelonephritis
Uncomplicated = no anatomical or neurological abnormalities of the urinary tract
What are the risk factors for an uncomplicated UTI compared to a complicated UTI?
What is pathogenesis?
Balance between host defences and organism virulence
What are the host factors for a 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
What are the host factors for an upper UTI?
May follow on from lower UTI
Vesico-ureteric reflux
Obstruction (eg calculus, stricture)
What is the pathogenesis of a UTI?
- 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 and proteases
- Colonisation of the kidneys
- Host tissue damage by bacterial toxins
- Bacteremia
What 3 factors does bacterial virulence depend on?
- Adherence
- Invasion
- Evasion
How does UPEC acheive 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
How is a diagnosis of a UTI made?
Clinical symptoms
Urine dipstick testing
Urine culture
What are the symptoms of cystitis?
bladder 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 so consider the diagnosis among other causes.
What are the symptoms of pyelonephritis?
fever, rigors, loin pain
renal angle tenderness
often lower UTI symptoms in addition
if pain radiation to groin - stone?
risk of bacteraemia
How is a clinical diagnosis of a UTI made?
Dipstick test at point of care. Main use to determine treatment if symptoms vague:
- Not diagnostic on their own
- Not useful if >65y or if catheterised
- Look for nitrites, leucocytes and red blood cells (RBC)
Don’t need to send urine for culture in simple 1st episode cystitis in a non-pregnant adult female
What are the NICE guidelines on diagnosing UTIs in females under 65?
How is a laboratory diagnosis of a UTI made?
Send to lab for culture
- pregnant, children, men, elderly, pyelonephritis, recurrence, failed treatment, abnormal urinary tract, renal impairment
Principles of a urine culture:
Urine in the bladder should be sterile in the absence of a UTI
However, it can be contaminated by bacteria colonising the distal urethra, or 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.
Also minimise the growth of any contaminants by rapid transport to lab (<4h), and/or boric acid preservative and/or refrigerate
What types of urine specimens are there?
Midstream urine
Suprapubic aspirate
Catheter urine
acute
intermittent self catheterisation
indwelling
Not recommended: clean catch urine; bag urine; pad urine.
How does a patient collect a mid stream urine sample?
What is the use of boric acid in midstream urine samples?
The presence of boric acid helps to maintain the microbiological quality of the specimen, it prevents cell degradation and overgrowth of organisms that can occur if the sample is not analysed within 4 hours of collection.
However, boric acid can cause false
negative culture if urine not filled to correct mark on specimen bottle and can affect urine dipstick tests
How is a laboratory diagnosis made using microscopy?
White cells represent inflammation in the urinary tract
Automated urine analysers in lab scan for red cells, white cells and organisms
Discard without culturing if scan negative (unless immunosuppressed or neonate)
How is a laboratory diagnosis made using 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 >> true mixed infection
How is antibiotic treatment used for UTI?
Empiric treatment so need to consider:
- target organisms
- route of administration
- target site
- side effects
- resistance (known or likely)
What does this show?
Antibiotic sensitivity testing
The main risk factor for resistant E coli in the community is what?
The main risk factor for resistant E coli in the community is previous antibiotic treatment
How does antibiotic resistance vary?
Changes over time
Varies geographically
How do we know about antimicrobial resistance (AMR) rates?
Approximately 98% of hospital microbiology laboratories in England voluntarily 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
So a key recommendation of the English Surveillance Programme for Antimicrobial Utilisation and Resistance (ESPAUR) is sentinel surveillance, which base resistance estimates on AST data from specimens collected from a wider range of patients.
How are UTIs prevented?
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.
How do catheter associated UTIs develop?
Bacteria colonise the catheter and bladder at a rate of 3-5% people / catheter day
Removal of catheter will clear bacteria in most cases
Usually asymptomatic, but some will develop UTI, and bacteremia, sepsis and death may result.
21% of patients with an E coli bloodstream infection had UC inserted/ removed/ manipulated in prior 7days
It is estimated that _____% of CAUTI events are avoidable
It is estimated that 69% of CAUTI events are avoidable
How are CAUTIs prevented?
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 is a CAUTI diagnosed?
What is asymptomatic bacteriuria?
Best left untreated unless pregnant
Extremely common in elderly patients; organisms often lack virulence factors
Treatment is not benign – adverse effects, financial cost, development of resistant strains and risk of C. difficile infection
What is the difference between a relapse and 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 uropathogn
