Microbiology Flashcards
bacteria in the normal urinary tract
Urine in the kidneys, ureters and bladder is normally STERILE
The lower end of the urethra is colonised by bacteria (coliforms and enterococci from the large bowel)
Important to differentiate between pathogen vs colonizer
Implication of colonization differ by host
important to get good samples
complicated UTI?
systemic symptoms or urinary structural abnormaility/stones
bacteriuria
is bacteria present in urine
does not always mean infection esp/ in elderly patients or patients with catheters
important to determine if patient symptom
dipstick testing with those with catheter and elderly people is ineffective
cystitis
inflammation of the bladder (not always due to infection)
Host factors in UTI
organism:
type of organism
presence of virulence factors
expression of virulence factors
host:
genetic background
behavioral factors
underlying disease
risk for UTIs?
women»_space; me
short wide urethra
proximity of urethra to anus
increased risk with sexual activity, pregnancy
catheterized patients
abnormalities of the urinary tract
routes of infection (ascending infection)
common bacteria from bowel perineal skin lower end urethra bladder -> ureters -> kidneys
routes of infection bloodstream
uncommon bacteraemia seeded into kidneys multiple small abscesses bacteria in urine
commensals vs pathogens?
patient specific timing/transit/storage specimen type dipstick vs culture culture media microscopy interpretation of sample - according to whether It is relevant to the presentation of the patient
coliforms
gram negative bacilli - the biggest cause
E. coli
(lactose fermenters) aerobic
other lactose fermenters
e.coli klebsiella spp enterobacter spp serrate spp citrobacter spp.
pseudomonas a coliform?
not a coliform but does cause UTIs
what allows E.coli infection?
endotoxin
fimbriae - allows for attachment to host
Proteus sp
particularly implicated in big stones struvite stones (triple phosphate stones) (staghorn calculi)
what does proteus sp smell like?
foul smelling, burnt chocolate
swarming cultures
produces urease which breaks down ammonia which increases urinary pH - precipitation of salts
