Microbiology Flashcards
What is a lower UTI?
infection confined to the bladder
What is an upper UTI?
infection involving the ureters and kidney - pylonephritis
Which parts of the urinary tract are normally sterile?
bladder, ureters and kidneys
Which parts of the urinary tract are not normally sterile?
urethra - colonised by coliforms and enterococci due to proximity to the large bowel
What is a complicated UTI?
UTI complicated by systemic symptoms or abnormal structure
What is bacteriuria?
bacteria is present in the urine but does not always indicate infection e.g. catheter or elderly patient
What are the risk factors for UTIs?
female>male due to shorter, wider urethra, close to anus
increased risk with sexual activity or pregnancy
catheterised patients
structural abnormalities
What are the two routes of infection for UTI?
Ascending
Bloodstream
Describe ascending UTIs?
most common
bladder -> ureter -> kidney
often E.coli as they have fimbrae that can climb up the ureters
bacteria from bowel
Describe bloodstream UTIs?
less common
often septicaemia or bacteriaemia
multiple small abcesses seeded into the kidneys
What are the investigations done for a UTI?
specimen to lab for:
dipstick - nitrites and leucocytes
culture
microscopy - not routine
What must the urine specimen be transferred in?
must be sent in either a boricon container - contains boric acid which stops the bacteria from multiplying for around 24hours
OR
in a sterile universal container - must reach the lab within 2 hours
What type of urine sample is needed?
mid stream sample - urine passed from the urethra will initially get contaminated with bacteria from the peritoneum or lower urethra
What is the presentation of a UTI (mainly lower)?
dysuria - pain passing urine
frequency of urination
change in nocturne
haematuria
What are the signs of an upper UTI?
loin pain
fevers
rigors
What are the main pathogens that cause UTIs?
E.coli Proteus Kleibsella Enterbacter Serratia Citrobacter Maganella Providericia
What is the gram stain and classification of pathogens that cause UTIs?
gram negative coliforms
What is the one organism that is not a coliform that can cause a UTI?
psuedomonas - it is a gram negative bacillus
How does a UTI caused by proteus present?
STAG HORN CALCULI
produces urase which breaks down urea to form ammonia which increases urinary pH and precipitation of salts
foul smelling, burnt chocolate
What is the only oral antibiotic that treats pseudomonas?
ciprofloxacin
What gram positive organisms can cause UTIs?
enterococcus faecalis and fasecium - most commonly aquired in hospital not in normal healthy people
staph saphrophyticus - coagulase negative staph, usually affects women of child bearing age
stay aureus - in bacteraemia
What is the diagnostic criteria for UTIs?
Kass Criteria
>10^5 organisms/ml = significant/probable UTI
10^4 organisms/ml = repeat - may be contaminated may be infection
<10^3 organisms/ml = not significant
What is a genuine UTI normally due to?
just one organism - if more than 2 its probably not significant
What is the action of ciprofloxacin?
inhibits bacterial DNA gyrase - not used in pregnant women or young children
What is antibacterial cystitis/urethral syndrome?
patient has symptoms of UTI, there are pus cells present in the urine but no bacterial growth on culture
may be due to urethral trauma, urethritis caused by STI, or just early phase of UTI
What is honeymoon cystitis?
urethral trauma due to sexual activity - presents with same symptoms as a UTI
What can help honeymoon and antibacterial cystitis and urethral syndrome?
alkalising the urine
What is asymptomatic bacteriuria?
bacteriuria >10^5 but the patient is asymptomatic so is detected incidentally - no treatment is needed
When is treatment needed for asymptomatic bacteriuria?
in prengancy
When are pregnant women screened for aysymptomatic bacteriuria?
1st antenatal unit appointment
What are the risks of not treating asymptomatic bacteriuria in pregnant women?
can progress to pylonephritis
and cause intra uterine growth retardation or premature labour
When shoud catheratised patients be given antibiotics for bacteriuria?
IF THEY HAVE SYMPTOMS
What is the treatment of a complicated UTI/pylonephritis/urosepsis in hospital?
amoxicillin and gentamicin IV - 3 days
step down: co trimoxazole PO
cotrimoxazole if pen allergic
What is the treatment of a complicated UTI/pylonephritis/urosepsis in primary care?
coamoxiclav PO - 14 days
cotrimoxazole if pen allergic
What is the treatment of a female lower UTI?
Nitrofuratoin or Trimethoprim PO - 3 days
What is the treatment of a male lower UTI?
Nitrofuratoin or Trimethoprim PO - 7 days
What are the characteristics of gentamicin?
IV only avoid in pregnancy narrow therapeutic index gram -ve cover only to be given for 3 days
What are the characteristics of Trimethoprim?
NOT FOR 1ST TRIMESTER
inhibits folic acid synthesis
(part of cotrimoxazole)
oral
What are the characteristics of Nitrofurantoin?
NOT FOR 2ND OR 3RD TRIMESTER - can cause neonatal haemolysis AVOID IN BREAST FEEDING AND CHILDREN < 3 oral only used in lower, uncomplicated UTIs doesnt treat proteus or pseudomonas
What are the characteristics of co-amoxiclav?
combo of amoxicillin and clauvulanic acid (beta lactamase inhibitor)
What are the characteristics of Pivmecillinam?
oral
treats lower, uncomplicated UTIs
has activtiy against ESBLs
NOT FOR PREGNANCY
What are the characteristics of Temocillin?
IV
has activity against ESBLs
useful for complicated UTIs/urosepsis - patients whose renal function is too poor for gentamicin
What are the characteristics of Cefalexin?
oral
only used when amoxicillin and trimethoprim are resistnat
1st generation cephalosporin
Name some antibiotics that might treat ESBLs?
nitrofurantoin pivmecillinam fosfomycin temocillin meropenem entrapenem
What are carbapenem producing enterobactams?
gram -ve coliform/bacilli that are resistant to meropenem - resistance is plasma mediated
How is ESBLs resistnace carried?
on a plasmid
