Microbiology Flashcards
Define a UTI
The presence of micro-organisms in the urinary tract that are causing clinical infection
Differentiate between an Upper and Lower UTI
Lower UTI = infection confined to bladder (cystitis)
Upper UTI = infection involving ureters +/- kidneys (pyelonephritis)
The lower end of the urethra is usually colonised by what bugs and why?
bacteria (coliforms and enterococci from the large bowel - due to proximity of anus to urerthra)
What is meant by a complicated UTI?
Pt has:
systemic symptoms
OR urinary structural abnormality /stones
Bacteruria does NOT always mean infection. TRUE/FALSE?
TRUE - Bacteriuria just means bacteria present in urine
does not always mean infection,
esp. in elderly patients or patients with catheters
Cystitis is caused by an infection. TRUE/FALSE?
FALSE
Cystitis is inflammation of the bladder
(not always due to infection)
Why are women at more risk of a UTI than men?
- short wide urethra
- proximity of urethra to anus
- increased risk with sexual activity, pregnancy
What are the two main routes of infection with a UTI?
- Ascending infection
- bloodstream
What bacteria is usually responsible for UTIs?
E-coli
What types of bacteria can be responsible for UTIs?
Lactose fermenting Coliforms (ecoli, Kelbsiella, enterobacter etc.)
Lactose non-fermenting coliforms (proteus, providencia)
Pseudomonas (Gm -ve bacilli but NOT a coliform)
What features of E-coli contribute to its virulence?
Endotoxin = released in sepsis Fimbriae = allow to adhere to the wall of urethra and climb upwards
Describe when proteus would normally be found?
in Struvite Kidney stones
Describe the presentation of proteus in the lab
Foul smelling (burnt chocolate) Swarming cultures
What does proteus produce and what does this cause?
Produces urease
=> breaks down urea to form ammonia (NH4+)
=> increases urinary pH - precipitation of salts
When would you suspect a pseudomonas UTI?
Associated with catheters and instrumentation
What antibiotic is the only oral option for a pseudomonas infection?
resistant to most oral antibiotics
except ciprofloxacin
How does ciprofloxacin work?
Inhibits bacterial DNA gyrase
=> prevents “supercoiling” of bacterial DNA
In what patients should ciprofloxacin be avoided?
young children
pregnant women
What bugs does ciprofloxacin NOT cover?
Staph aureus or MRSA
Where is an infection such as Enterococcus faecalis
most likely acquired?
In hospital
Who is usually affected by Staphylococcus saphrophyticus UTIs?
women of child bearing age
What symptoms indicate a lower urinary tract infection?
dysuria (pain passing urine)
frequency of urination
nocturia
haematuria
What symptoms may indicate an upper urinary tract infection?
Fever
Rigors
Loin pain
When do you want to take a specimen to check for evidence of UTIs?
- Midstream specimen (as first pass of urine will be contaminated)
- Suprapubic aspiration
- Straight (in/out) catheter
What container can be used for a urine specimen where it will take longer than 2 hrs to reach the labs?
Boricon container
contains boric acid to stop bacterial multiplying
works for ~24 hrs
What patients should NOT undergo dipstick urine testing?
DO NOT DIPSTICK URINE OF THE ELDERLY
DO NOT DIPSTICK CATHETER SPECIMENS
When is microscopy of urine used?
If cultures have been identified but the lab wishes to be more specific with the diagnosis
Over what number of bacteria in a urine specimen would indicate an infection?
> 10^5
What is an abacterial cystitis?
Patient has symptoms of UTI
Pus cells present in urine, but no significant growth on culture
What can cause an abacterial cystitis?
early phase of UTI
urethral trauma - “honeymoon cystitis”
urethritis caused by chlamydia, gonorrhoea
If antibiotics cannot be given, what treatment can provide symptomatic relief in abacterial cystitis?
Alkalinising agents
When is asymptomatic bacteruria treated?
Treated with antibiotics in pregnancy.
If left untreated:
- may progress to pyelonephritis
=> lead to intra-uterine growth retardation (IUGR) or premature labour
When should catheterised patients be given antibiotics?
When there is evidence of symptoms of infection
How is a female Lower UTI treated?
Trimethoprim or nitrofurantoin orally (3 days)
How is an uncatheterised male UTI treated?
Trimethoprim or nitrofurantoin orally (7 days due to prostatism risk)
How is a complicated UTI/ pyelonehritis treated in the community?
Co-amoxiclav or co-trimoxazole (14 days)
How is a complicated UTI/ pyelonehritis treated in hospital?
Amoxicillin and gentamicin IV for 3 days
Why is gentamicin only used in hospital settings?
Can only be given IV
Narrow therapeutic index before toxicity
What antibiotic should be given if a patient has an ESBL infecting organism?
Pivmecillinam (oral) and Temocillin (IV)
When should trimethoprim be avoided?
1st trimester (3 months) of pregnancy
Why is amoxicillin not used first line to treat UTIs?
> 50% of coliforms including Ecoli are now resistant
When would cefelexin potentially be used to treat a UTI?
If organism is amoxicillin and trimethoprim resistant
What patient group is Temocillin useful for?
Useful in patients whose renal function is too poor for gentamicin
NOT as effective as gentamicin clinically
