Microbiology Flashcards
What is a UTI?
prescence of micro-organisms in the urinary tract that are causing clinical infection
compare a lower and upper UTI?
lower: confined to bladder
upper: ureters +/- kidneys
what is a complicated UTI?
UTI with systemic sepsis, stones or urinary structural abnormality
what is bacteriuria?
presence of bacteria in the urine
what is cystitis?
inflammation of the bladder
compare the length of antibiotic courses in a complicated an uncomplicated UTI?
uncomplicated: short course
complicated: long course
why can pregnancy increase risk of UTI?
pressure on bladder can cause incomplete emptying
stasis of urine can lead to infection
what group of organisms are the most common causative organisms of UTI?
coliforms
which organisms is the most common cause of a UTI?
E. coli
which UTI causative organism is associated with formation of calculi?
proteus sp (a type of coliform)
why does proteus UTI cause calculi formation?
proteus produces urease which breaks down urea to ammonium
this increased urinary pH leads to salt precipitation
what type of patient does Staph saphrophycticus cause UTIs in?
women of child bearing age
pseudomonas UTI is associated with what risk factor?
catheters and urinary tract instrumentation
what is the only oral antibiotic which pseudomonas is sensitive to?
ciprofloxacin
why should ciprofloxacin be avoided unless necessary?
C. dif risk
what are the 3 main symptoms/signs of a lower UTI?
dysuria
frequency/nocturia
haematuria
what 3 main symptoms/signs of a UTI suggest upper urinary tract involvement?
fever
loin pain
rigors
what part of the stream do you want for a urine specimen?
mid-stream
what kind of patients are ‘clean catch’ urine specimens obtained in?
children
elderly
what kind of patients are bag urine specimens obtained in?
babies
what kind of patients are suprapubic aspiration urine specimens obtained in?
babies
compare red top and white top urine containers?
red top- boricon preservative container
white top- sterile universal container
compare the time period for specimen reaching the lab in red and white top urine containers?
red- 24 hours
white- 2 hours
what does boricon preservative do in a red top container?
prevents bacterial multiplication
what 4 things on urine dipstick may be present in infection?
leukocytes
nitries
protein
blood
compare coliforms and entercoccus sp on the presence of nitrites on urine dipstick?
coliforms: present
enterococcus: not present
(only gram negs convert)
what kind of bacterial are coliforms?
gram neg bacilli
why might urine microscopy be done for a suspected UTI?
urgent cases
what is Kass’s criteria for UTI?
more than 10^5 organisms/ml- probable UTI
10^4 organisms- repeat specimen
less than 10^3 organisms- not significant
what type of patients does the Kass criteria for UTI apply to?
women of child bearing age
what antibiotics are ESBL (extended spectrum beta-lactamase) organisms resistant to?
all cephalosporins
almost all penicillins
what imported food stuff do you see ESBL (extended spectrum beta-lactamase) organisms in?
imported chicken
what are carbapenamase-producing enterobacteriaceae? (CPE)
gram negative bacilli (coliforms) that are resistant to meropenem
(ie resistant to all current antibiotics)
what sub-continent are carbapenamase-producing enterobacteriaceae (CPE) associated with?
indian sub-continent
in women, how long are antibiotic courses for an uncomplicated lower UTI?
3 days
what are the 4 first line antibiotics for UTI?
amoxicillin (IV, PO)
trimethoprim (PO)
nitrofurantoin (PO)
gentamicin (IV)
why is amoxicillin not a goot choice for empirical treatment of a UTI?
50% of E.coli strains are resistant
what is the action of trimethoprim?
inhibits bacterial folic acid synthesis
what trimester must trimethoprim be avoided in and why?
first trimester, inhibits folic acid so can cause spina bifida
what combination is co-trimoxazole?
trimethoprim and sulphamethoxazole
what serious dermatological side effect can occur with co-trimoxazole?
Steven- Johnson’s syndrome
why can nitrofurantoin not be used in upper UTI?
because it only becomes activated in the urine
why must gentamicin only be prescribed for 3 days?
because of toxicity to CN VIII (deafness and balance problems) and kidneys
what is the empirical treatment for a female lower UTI?
trimethoprim or nitrofurantoin PO 3 days
what is the empirical treatment for a uncatheterised male UTI?
trimethoprim or nitrofurantoin PO 7 days
what is the empirical treatment of a complicated UTI or pyelonephritis within GP?
co-amoxiclav or co-trimoxazole PO 14 days
what is the empirical treatment of a complicated UTI or pyelonephritis within hospitial?
amoxicillin AND gentamicin IV 3 days
then step down dguided by antibiotic sensitivities
compare the treatment asymptomatic UTI (ie bacteraemia) in non-pregnancy and pregnant women?
non-pregnant: no treatment
pregnant: antibiotic treatment
what is the empirical treatment for UTI/bacteraemia for a pregnant woman?
1/2 trimester: nitrofurantoin (7 days)
3 trimester: trimethoprim (7 days)
all trimesters cefalexin (7 days)
why should pregnnat women with bacteriauria be treated with antibiotics even if asymptomatic?
may progress to pyelonephritis
may lead to intra-uterine growth retardation
may lead to premature labour
