urinary tract infections Flashcards
how common are UTIs
2nd only to resp infections
50% women, many recurrent. 3X more common in infant boys than girls and rare in men until old age (prostate enlargement)
20% elderly have asymptomatic bacteria.
Develop from catheters.
consequences of UTIs
societal and individual cost - healthcare, time misused freq recurrences uncontrolled infection/sepsis real damage in young children preterm birth antimicrobial resistance and CDI risk
how are UTIS classified
uncomplicated- no anatomical or neurological abnormalities of UT
Uncomplicated lower- cystitis, urethritis, prostates, epididmyo-orchitis
uncomplicated upper - acute pyelonephritis
risk factors for UTIs
female, old and young catheters immunosuppression UT abnormalities AB exposure
what is pathogenesis
balance between host defences and organism virulence
host factors for Lower UTI
obstruction-prostatic hypertrophy, urethral valves/stricture
poor bladder emptying - MS. SCI, bladder diverticula, pelvic floor disorders
catheterisation
sex
vesicle-enteric fistula
diabetes
genetics - non secreters of ABH blood antigen esp premenopausal, variable expression CXCR1 receptor ifor neutrophil activation
host facts for upper UTI
may follow from lower UTI
vesicle-ureteric reflex
obstruction (eg calculus, stricture)
pathogenesis of UTIs
contamination of the periurethral area with uropathogen from gut
colonisation of urethra, migration and invasion of bladder
mediated by pili and adhesins
neutrophil infilt
bacterial multiply, immune system subversion
biofilm forms
epithelial damage by bad toxins and proteases
colonise kidney
host tissue damage by bacteria toxins
bacteremia
what does bacterial virulence depend on
adherence
invasion
evasion
how is adherence involved in UTIs
in bladder uropathogenic E.coli (UPEC) express type 1 pili essential for colonisation, invasion and persistence
p-pili confer tropism to kidney
highly adhesive so proficient in retrograde urethral ascent
How invasion involved in UTIs
pilus bind to host cell
actin rearrange in host cell to take up bacteria
protected from antibiotics and host defences
how is evasion linked to UTIs
escape eviction by going to cytoplasm and multiplying
filamentous morphology so harder to kill
excrete things to aid nutrient acquisition
how is a UTI diagnosed
Clinical symptoms
Urine dipstick testing
Urine culture
clinical symptoms of cystitis
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.
clinical 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
when is a dipstick used
main use if symptoms vague eg not diagnostic
not useful if >65y or catheter
look for nitrites, leucocytes, RBCs
how is a UTI diagnosed in a female <65
dysuria, new nocturia, cloudy urine
if only 1 symptom dipstick
if none look for other symptoms and dipstick
when should a UTI be diagnosed by sending to a lab for a culture
pregnant, children, men, elderly, pyelonephritis, recurrence, failed treatment, abnormal urinary tract, renal impairment
principles of a urine culture
urine sterile if no UTI
contaminated by bacteria in distal urethra or hands/genitals
mid stream urine avoids this (no initial or end micturition)
rapid transport, boric acid preservative/fridge to avoid growth of contaminants
urine specimens
MSU Suprapubic aspirate Catheter urine acute intermittent self catheterisation indwelling
what does boric acid do in MSU
boric acidhelps to maintain the microbiological quality of thespecimen
prevents cell degradation and overgrowth of organisms that can occur if thesampleis not analysed within 4 hours ofcollection.
can cause false
negative culture if urine not filled to correct mark on specimen bottle and can affect urine dipstick tests
microscopy of UTIs
WCs -inflammation in UT
Automated urine analysers in lab scan for RCs, WCs and organisms
Discard without culturing if scan negative (unless immunosuppressed or neonate)
culture and AB sensitivity of UTIs
quantitative
>10^5 organisms per ml is “significant bacteriuria” (in MSU only)
ie, probably not contaminants (90% specific)
Mixed growth may represent contamination»_space; true mixed infection
what should be considered in treating a UTI
Empiric treatment need to consider: target organisms route of administration target site side effects resistance (known or likely)
how can a UTI be 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
what is a catheter associated UTI
Bacteria colonise catheter and bladder, 3-5% people/day
Removal of catheter will clear bacteria in most cases
Usually asymptomatic
some develop UTI, and bacteremia, sepsis and death
21% of patients with an E coli bloodstream infection had UC inserted/ removed/ manipulated in prior 7days
prevention of catheter associated UTIs
Use for good reason eg Mx of urine output in acutely unwell Mx of acute retention/obstruction Selected surgical procedures Aseptic insertion Closed drainage system Daily review of removal needs Consider alternatives
signs of a CAUTI
Fever rigors new onset confusion lethargy back pain pelvic pain acute haematuria
how is a CAUTI diagnosed
urine dipstick not used - contamination, non visible haematuria, normal findings when usually would = UTI
urine sample pre ABs, post diagnosis as will help guide treatment but won’t diagnose
how is asymptomatic bacteriuria treated
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 a UTI relapse
the same uropathogen causes UTI symptoms within 2 weeks of completing appropriate AB treatment
what s a UTI 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
