UTI Flashcards
define cystitis
inflammation of the bladder, often caused by infection. – lower UTI
define bacturia
the presence of bacteria in the urine.
Not necessarily abnormal – common in older pts – want to flush out the commensals – so need MSU
when do you treat asx UTI
in pregnant women esp for E coli – associated adverse outcomes.
in children – may be indication that they have an abnormal urinary tract
definition of uncomplicated UTI
infection in a structurally and neurologically normal urinary tract.
women
definition of complicated UTI
infection in urinary tract with functional or structural abnormalities (including indwelling catheters and calculi)
Structural abnormality, urethral valve in children.
- In pregnancy
- men - longer urethra so harder for bacteria to ascend
- children
- hospitalised/health care - esp if catheter
prevalence of UTI
1-3% prevalence in young, nonpregnant women
common
main organisms responsible for UTI
mostly caused by single bacterial species.
E coli is most frequent in acute infection
only a few serogroups of E. coli, O1, O2, O4, O6, O7, O8, O75, O150, and O18ab, cause a high proportion of infections
if other organisms - suggests structural problem/commensal
depends on the virulence factors of bacteria whether they can ascend to bladder, and further to cause pyelonephritis - more virulence factors, more severe infection - some factors favour cystitis, some pyelonephritis and some asx bacteriuria
other organisms that cause UTI and what they are associated with
Proteus mirabilis – associated with stones (renal/ureteric calculi)
Klebsiella aerogenes – resisntant gram –ve, in hospitalisted, catheter, stent, post-op, Abx. don’t have same virulence factor as E coli to go up epi – so adhere to catheter and are pushed up. Think is there something wrong with the response
pseudomonas - prosthetic material
Enterococcus faecalis
Staphylococcus saprophyticus – does have virulence factor – common cause of UTI in young women
Staphylococcus epidermis
enterobacter
enterococci
staphylococci
Staph are colonisers – don’t usually cause problems
antibacterial host defences in the urinary tract
- urine - osmolality, pH, organic acids
- urine flow and micturition
- urinary tract mucosa (bactericidal activity, cytokines)
Flow will be disrupted with catheter – flow wont push bacteria away from the epithelium
summarise ascending UTI
urethra colonised with bacteria
in women - urethra is short and close to warm, moist vulva and perineam areas - making contamination likely
organisms colonise the vaginal introitus and periurethral area before urinary infection results - if correct virulence factor -> infection
most common - E coli and staph
bacteria multiply in bladder -> ureters esp if vesicoureteral reflux present -> renal pelvis and parenchyma
if catheter, preg, stent, stone – pass up ureter – pyelonephritis
If static urine – eg BPH – great resevior for bacteria to be – increase risk
why do abnormalities in renal tract -> infection
obstruction inhibits flow -> stasis
causes of obstruction
Mechanical
Extrarenal:
* valves, stenosis, or bands
* calculi
* extrinsic ureteral compression from a variety of causes; and benign prostatic hypertrophy
Intrarenal:
* nephrocalcinosis,
* uric acid nephropathy,
* analgesic nephropathy,
* polycystic kidney disease,
* hypokalemic nephropathy
* renal lesions of sickle cell trait or disease
Neurogenic malfunction
- poliomyelitis,
- tabes dorsalis,
- diabetic neuropathy,
- spinal cord injuries
how does vesicoureteral reflux -> infection
by maintaining a residual pool of infected urine in the bladder after voiding
summarise the haematogenous route of infection for UTI
kidney site of abscesses if have staph aureus bacteremia or endocarditis, or both
staph aureus seed into kidney -> abscess -> excreted in urine - treat as systemic infection: IV flucloxacillin
if ascending -> pyelonephritis -> bacteraemia
if haematogenous spread: bacteraemia -> staph aureus in urine
sx of UTI in children <2yrs
non-specific
failure to thrive
vomiting
fever
evidence of systemic infection
diagnostic considerations for UTI in men
Uncomplicated UTI uncommon in men
Need to look for other causes – STI
Worry about upper UTI
Prostitis
Need to send MSU – more likely more unusual organisms
Dipsticks poor at ruling out infection
diagnostic considerations for UTI in men
Uncomplicated UTI uncommon in men
Need to look for other causes – STI
Worry about upper UTI
Prostitis
Need to send MSU – more likely more unusual organisms
Dipsticks poor at ruling out infection
ix for UTI > 65yrs
Dipstick not common because asx bacteria is common
Mainly looking at sx, and whether catheterised
when to send urine for culture
how do you interpret a urine culture result if suspect UTI
interpret in parallel with clinical picture
Presence of a bacteria does not mean that it is causing a problem
so less than 10(4) is not significant >10(5) is significant. But even significant growth doesn’t = problem
Don’t report mixed growth – means that it is a poorly taken sample or colonisation
If V high numbers of 1 predominant organism – then they will report that organism
Wont be reported as no growth – it would be mixed growth/no sig growth
Report on epithelial cells – (squamous – line the lower 1/3 of urine) – so if you see them it suggests not MSU and therefore it is a poorly taken sample and organisms may reflect a colonisation
Red cells – if persistent red cells – refer to urology
WCC – infection of urinary tract- could still not be causing a problem. Consider STI/unusual organisms eg TB – urine cultures don’t pick up TB
lab testing for UTI
MC&S
Chromogenic agar – different organisms go different colour
Get a loop of urine – spread across agar – count the colonies – multiplication factor
interpretation of microscopy for UTI
Can get WC for other things like STI
Sq epi cells – urine from lower urethra
Rx of UTI
empirical therapy
community lower UTI
local guidance
3 days of therapy with standard doses for treatment of uncomplicated lower tract infection in women
7 days in men or women with history of previous urinary infection caused by antibiotic-resistant organisms or more than 7 days of symptoms - more likely upper UTI
Rx of catheter associated UTI
Gentamycin
Take nitro after voided so it sits in the bladder and has the best effect – if have a catheter bladder is constantly draining so nitro wont be the best choice
Bacteria can sit on the catheter so nothing will help the patient
