Microbiology 6: Urinary Tract Infections Flashcards
What is the most common causative organism for UTI’s ?
E.coli
Name a virulence factor of some E.Coli serotypes that make them well adapted to cause UTIs ?
P-fimbriae
These allow the bacteria to adhere to the epithelium and therefore ascend
Which commensal skin bacteria is a rare cause of UTI but is more common in patients with Prosthesis e.g they have a long term in dwelling catheter ?
Staphylococcus epidermidis
Which 4 organisms are more common causes of UTIs in people with structural abnormalities ?
- Proteus mirabilis (kidney stones)
- Pseudomonas
- Klebsiella aerogenes (occur in abnormal urinary tracts - stones, neuro + anatomical abnormalities)
- Enterococcus faecalis
List 4 neurological causes of obstruction in the urinary tract ?
Poliomyelitis
Tabes dorsalis
Diabetic neuropathy
Spinal cord injury
Which organisms can cause a UTI which is negative for nitrites but positive for leucocytes on urine dipstick ?
- (Non coliform bacteria)
- Staphylococcus saphrophyticus
- Enterococcus faecalis
- Could also be urethral syndrome
List 3 ways you could collect a urine sample ?
Mid stream urine (MSU) - PREFERRED
Catheterisation
Supra Pubic aspiration
NB do the last 2 in certain situations to try and get a clean sample e.g. in young children
What is the most common causes of Sterile pyuria? (raised WCC but no growth on culture)
Other causes (5)
Prior treatment with antibiotics
Others:
- calculi: inflammation but not infection
- catheterisation
- bladder neoplasm
- TB - rare
- STD (chlamydia)
What colour is E.coli on chromogenic agar ?
Pink
What is the most common treatment for an uncomplicated UTI ?
Empirical treatment - Nitrofurantoin/Trimethoprim (3 days)
Although the resistance of E.coli is rapidly increasing so check with local governance.
Which infections occur in patients that have indwelling catheters ?
Candida
What is the most common treatment for Pyelonephritis ?
Co-amoxiclav +- gentamicin
Which organism that is not E.Coli tends to cause UTIs particularly in young women (2nd most common cause of UTI)?
Staphylococcus Saphrophyticus
Name a congenital abnormality that causes oligohydramnios and can cause Potter’s syndrome in male neonates?
Posterior urethral valve (PUV)
Give an example of a paediatric cause of Kidney scarring ?
Vesicoureteric reflux (VUR)
define uncomplicated UTI
infection is in a structurally and neurologically normal urinary tract - usually refers to lower UTI in women
define complicated UTI
infection in a urinary tract with functional or structural abnormalities (including indwelling catheters and calculi)
- men: greater urethral length so considered complicated (basically harder for them to get infected, so if they are, then more likely complicated reason)
- pregnant
- children: valves
what is staphylococcus saprophyticus
- coagulase negative
- 2nd commonest cause of UTI in young women (after Escherichia coli)
- P fimbrae allows adherence to the epithelium
how can reflux cause UTIs
- vesicoureteric reflux
- residual pool of urine in the bladder after urination that can go back up to kidneys rather than leaving the body
- can cause kidney scarring
symptoms of UTI in nonates and children <2 yrs
- non specific
- failure to thrive
- vomiting
- fever
symptoms of UTI in children >2
- frequency
- dysuria
- abdominal or flank pain
what do the following of urine culture suggest:
- white cells pyuria
- squamous epithelial cells
- white cells pyuria - infection
- squamous epithelilal cells - contaminations
Mx of fungal urinary tract infection
Why is it difficult to treat?
- PO Fluconazole is the treatment of choice BUT there is increased resistance
- If fluconazole is NOT effective, use non-liposomal amphotericin B
Difficult to treat since Lots of antifungals used do not get excreted in the urine
how many single organisms must be cultures to diagnose UTI
>10^5 CFU/mL with urinary symptoms
