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
Especially in elderly, and those with catheters
Why is UTI more common in women? List other risk factors for UTI
Short, wide urethra
Urethra near anus
Pregnancy
Catheterised patients
Abnormality of UT
Diabetes
Immunosuppressed patients e.g HIV/ AIDs
What is the most common route of infection in UTI? Name another route of infection
Ascending infection - bacteria from bowel/bladder rises upwards through ureters to the kidneys
Bloodstream (bacteraemia/ septicaemia)
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 (struvite triple phosphate stones)
Which enterococcus - faecalis or faecium - is quite resistant to antibiotics?
Enterococcus faecium
Which particular strain of Staphylococcus is associated with UTI? Who is it usually found in?
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 (lower) UTI
CYSTITIS
Dysuria
Frequency/nocturia
Haematuria
What clinical features suggest an upper UTI?
PYELONEPHRITIS Fever and chills Loin pain Rigors Nausea, vomiting
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? Which organism does not give a positive nitrite test on dipstick?
Bacteriuria
(bacteria reduce nitrate to nitrite)
Enterococcus spp.
What substances are looked for on urine dipstick?
Leukocytes (WBC)
Nitrites
Protein
Blood
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? Name an antibiotic that can be used to treat?
Cephalosporins
Penicillins
Meropenem
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
Only reaches effective concentration in bladder urine
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 for 14 days
State empirical antibiotic treatment for complicated UTI/pyelonephritis in hospital
Amoxicillin + gentamicin
co-trimoxazole if pen-allergic
What is the first line investigation when significant bacteriuria is suspected?
Urine culture
What are the causes of abacterial cystitis? How should it typically be managed?
Early UTI
Urethral trauma ‘honeymoon cystitis’
Urethritis (chlamydia, gonorrhoea)
Alkalise urine, empty bladder after sex, fluids
Abacterial cystitis should be managed with antibiotics in what group of patients? What are the consequences of not treating?
Pregnancy
Pyelonephritis, IUGR, premature labour
Which antibiotic is used to treat UTI in pregnancy? What is the main side effect to be aware of?
Cephalexin
C.diff infection
What is the indication for antibiotics in a catheterised patient with UTI? What is the consequence of unecessary antibiotics?
> 10^5 organisms/ ml only if supporting symptoms
Colonisation of catheter with resistant organisms
Risk of C.diff infection
