Microbiology Flashcards
Urine in the kidneys, ureters and bladder is normally sterile. True/False?
True
Which organisms usually colonise the lower end of the urethra?
Coliforms
Enterococci
(from large bowel)
Define “UTI”
Presence of microorganisms in the urinary tract that are causing clinical infection
Lower UTI denotes infection confined to where?
Bladder (cystitis)
Upper UTI denotes infection spreading to where?
Ureters +/- kidneys (pyelonephritis)
Bacteriuria (presence of bacteria in urine) always indicates a UTI. True/False?
False
Why is UTI more common in women?
Short, wide urethra
Urethra near anus
Pregnancy
What is the most common route of infection in UTI?
Ascending infection - bacteria from bowel/bladder rises upwards through ureters
List the main causal organisms of UTI
E. coli
Klebsiella
Enterococci
Proteus
Which bacteria is associated with the formation of calculi?
Proteus sp.
Produces urease which breaks down urea to form ammonia (increases pH), precipitating salt formation
Which enterococcus - faecalis or faecium - is quite resistant to antibiotics?
Enterococcus faecium
Which particular strain of Staphylococcus is associated with UTI?
Staph. saphrophyticus (coag. -ve)
Particularly in women of child-bearing age
Which organism is associated with causing UTI in catheterised patients?
Pseudomonas
Which antibiotic is Pseudomonas not resistant to?
Ciprofloxacin
List the main symptoms and signs of UTI
Dysuria
Frequency/nocturia
Haematuria
What clinical features suggest an upper UTI?
Fever
Loin pain
Rigors
When taking a urine sample to check for UTI, the first urine passed is assessed. True/False?
False
First urine is likely to be contaminated; collect mid-stream sample
List different ways of collecting urine specimens
Midstream bowl by patient Clean catch by nurse Bag urine (babies) Catheter specimen Suprapubic aspiration
Which container contains preservative that can prevent bacteria multiplying in a urine sample?
Boricon (red top) container
Works for 24hrs
If a urine sample is collected in a standard universal (white top) container, how quickly must it reach the lab?
Within 2 hours of collection
The presence of nitrites on dipstick suggests what?
Bacteriuria
bacteria reduce nitrate to nitrite
Which organism does not give a positive nitrite test on dipstick?
Enterococcus spp.
What is looked for on urine microscopy?
Pus cells +/- red cells
Define Kass’s criteria for diagnosing UTI in women of child-bearing age
Less than 10^4 organisms/ml - unlikely UTI
10^4 organisms/ml - possible (repeat)
More than 10^5 organisms/ml - probable UTI
ESBL-producing bacteria are resistant to which antibiotics?
Cephalosporins
Penicillins
Which antibiotics may be useful for ESBL-producing bacteria?
Nitrofurantoin Pivmecillinam Fosfomycin Temocillin Meropenem Ertapenem
Carbapenemase-producing enterobacteriaceae (CPE) are resistant to which antibiotics?
All current antibiotics!
Some antibiotics are metabolised and excreted by the liver. What is the significance of this?
Not useful for treating UTI
How is uncomplicated lower UTI in women treated usually?
3 day course of empirical antibiotic
List 1st line antibiotics for UTI
Amoxicillin
Trimethoprim
Nitrofurantoin
Gentamicin
List 2nd line antibiotics for resistant UTI
Pivmecillinam Temocillin Cefalexxin Co-amoxiclav Ciprofloxacin
Enterococcus faecalis is sensitive to amoxicillin. True/False?
True
Amoxicillin is good for empirical UTI treatment. True/False?
False
Resistant rate too high - only used if know organism is sensitive
Which antibiotic is usually used for empirical UTI treatment?
Trimethoprim
How does trimethoprim work? What is the significance of this?
Inhibits folic acid synthesis - thus not recommended in early pregnancy
Trimethoprim can be given as co-trimoxazole. What is a risk of this drug?
Causes Stevens-Johnson syndrome
Nitrofurantoin is only useful in uncomplicated lower UTI. True/False?
True
Should nitrofurantoin be avoided in pregnancy?
Yes
Can cause neonatal haemolysis
By definition, hospitalised UTI is usually treated by gentamicin. True/False?
True
Except in pregnancy; can cause ototoxicity
What is the maximum duration of prescription of gentamicin?
3 days
Which antibiotics have some activity against ESBL-strains?
Pivmecillinam
Temocillin
State empirical antibiotic treatment for female lower UTI
Trimethoprim/nitrofurantoin
State empirical antibiotic treatment for uncatheterised male UTI
Trimethoprim/nitrofurantoin
State empirical antibiotic treatment for complicated UTI/pyelonephritis in GP
Co-amoxiclav/co-trimoxazole
State empirical antibiotic treatment for complicated UTI/pyelonephritis in hospital
Amoxicillin + gentamicin
co-trimoxazole if pen-allergic
