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
