Urinary Tract Infections Flashcards
What is acute cystitis?
infection of the bladder
What is pyelonephritis?
infection of the kidney and renal pelvis
What is sterile pyruria?
puss in urine without bacterial growth
At what point does the urinary tract become sterile?
the bladder sphincter
What is the most common aetiological agent of UTIs?
E. coli
What is the most common gram positive cause of UTIs?
staph saprophyticus
What bacteria in the same family as E. coli is a cause of UTIs?
proteus species
What other bacteria cause UTIs (usually in hospitals)?
klebsiella, enterobacter, serratia, pseudomonas, enterococcus, staphylococcus
Do viral pathogens cause classical UTIs?
no
Which viruses shed asymptomatically in the urine?
CMV, rubella, polyomavirus (in immunocompromised patients)
Which virus causes haemorrhagic cystitis?
adenovirus
Which virus causes renal disease?
hantavirus
How do bacteria usually access the urinary tract?
ascending from the urethra via contamination from the anus
Which bacteria can infect the urinary tract from the blood?
staph aureus, salmonella typhi, TB
What are the features that give the urinary tract innate immunity?
epithelium is resistant, some bacteria dont like growing in urine, constant flushing effect or regular bladder emptying
Why do women get more UTIs than men?
because the urethra is shorter and straighter and closer to the anus
What will increase the risk of UTIs in infant males?
no circumcision
What else will increase the risk of UTIs?
heavily colonised distal urethra
What abnormalities will cause an increase risk of UTIs?
structural abnormalities and functional abnormalities which prevent bladder emptying e.g. horse shoe kidney, tumour, stones, enlarged prostate, neurological, vesico-ureteric reflux
What common foreign body will cause an increased risk of UTIs?
catheter
What feature do most E. coli have that helps them adhere and cause UTIs?
type 1 fimbria
What feature do some E. coli have that is specific for UTIs?
pylonephritis associated pili (PAP pili)
Is there one specific virulence factor that all uropathogenic E. coli share?
no
What enzyme does proteus have?
urease - to get energy from urea - ammonia as an end product
What features helps E. coli swim up ureters?
flagella
What are the symptoms of a UTI?
increase frequency of micturition with burning, possible fever, possible tenderness over bladder or kidneys
If you found the pathogen of a UTI in the blood what would it indicate?
pylonephritis
Why do you need to take a midstream urine sample?
the first part of the urine may have normal microbiota and the last part may have prostatic secretions
What is the significance of a pathogen in a bag sample of urine?
no significance- may be from the urine or may be from the skin or the gut - only significant if it is sterile
What is the significance of a pathogen in a supra pubic aspirate?
definitely the cause of the UTI
Why dont you collect from the bag of the catheter?
because the bacteria will have replicated
What number of white blood cells in the urine indicates infection?
> 10^5
Does a raised white cell count always mean infection?
no - could mean stones or tumours or other things - sterile pyuria
What does the presence of squamous epithelial cells indicate?
a poorly collected sample
What number of bacteria in a midstream sample indicates infection?
> 10^5 CFU
What does nitrites in the urine indicate?
there are bacteria - but not all bacteria will produced nitrites so if negative it is not definitive
Why should you check the pH of urine before giving treatment to alkalinise urine?
because if the urine is alkaline there are ammonia forming bacteria (proteus) and there is a risk of forming struvite stones
What antibiotic treatment is given for UTIs?
cephalexin or co-amoxyclav or trimethoprim
What antibiotic treatment is given for sepsis caused by pyelonephritis?
amoxycillin and gentamicin
When is asymptomatic bacteriuria significant?
in pregnancy - can be associated with premature
What defines recurrent UTIs?
more than 2 in 6 months
