Microbiology 6: Urinary Tract Infections

Question 1

What is the most common causative organism for UTI’s ?

Answer 1

E.coli

Question 2

Name a virulence factor of some E.Coli serotypes that make them well adapted to cause UTIs ?

Answer 2

P-fimbriae

These allow the bacteria to adhere to the epithelium

Question 3

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 ?

Answer 3

Staphylococcus epidermidis

Question 4

Which 4 organisms are more common causes of UTIs in people with structural abnormalities ?

Answer 4

Proteus mirabilis
Pseudomonas
Klebsiella aerogenes
Enterococcus faecalis

Question 5

List 4 neurological causes of obstruction in the urinary tract ?

Answer 5

Poliomyelitis
Tabes dorsalis
Diabetic neuropathy
Spinal cord injury

Question 6

Which organisms can cause a UTI which is negative for nitrites but positive for leucocytes on urine dipstick ?

Answer 6

(Non coliform bacteria)
Staphylococcus saphrophyticus
Enterococcus faecalis

Could also be urethral syndrome

Question 7

List 3 ways you could collect a urine sample ?

Answer 7

Mid stream urine (MSU)
Catheterisation
Supra Pubic aspiration

Question 8

What is the most common causes of Sterile pyuria? (raised WCC but no growth on culture)

Answer 8

Prior treatment with antibiotics

Question 9

What colour is E.coli on chromogenic agar ?

Answer 9

Pink

Question 10

What is thew most common treatment for an uncomplicated UTI ?

Answer 10

Empirical treatment - Nitrofurantoin/Trimethoprim (3 days)

Although the resistance of E.coli is rapidly increasing so check with local governance.

Question 11

Which infections occur in patients that have indwelling catheters ?

Answer 11

Candida

Question 12

What is the most common treatment for Pyelonephritis ?

Answer 12

Co-amoxiclav +- gentamicin

Question 13

Which organism that is not E.Coli tends to cause UTIs particularly in young women?

Answer 13

Staphylococcus Saphrophyticus

Question 14

Name a congenital abnormality that causes oligohydramnios and can cause Potter’s syndrome in male neonates?

Answer 14

Posterior urethral valve (PUV)

Question 15

Give an example of a paediatric cause of Kidney scarring ?

Answer 15

Vesicoureteric reflux (VUR)

Question 16

define uncomplicated UTI

Answer 16

infection is in a structurally and neuroogically normal urinary tract

Question 17

define complicated UTI

Answer 17

infection in a urinary tract with functional or structural abnormalities (including indwelling catheters and calculi

men, pregnant, children,

Question 18

what is staphylococcus saorophyticus

Answer 18

coagulase negative
associated with infections in young women
P fimbrae allows adherence to the epithelium

Question 19

what infections are common in the presence of structural abnormalities (UTIs)

Answer 19

proteus
pseudomonas 
klebsiella 
enterobacter
enterococci 
staphlococci

Question 20

how can reflux cause UTIs

Answer 20

vesicoureteric reflux
residual pool of urine in the bladder after urination
can cause kidney scarring

Question 21

symptoms of UTI in nonates and children <2 yrs

Answer 21

non specific
failure to thrive
vomiting
fever

Question 22

symptoms of UTI in children >2

Answer 22

frequency
dysuria
abdominal or flank pain

Question 23

what do the following of urine culture suggest:

• white cells pyuria
• squamous epithelial cells

Answer 23

white cells pyuria - infection

squamous epithelilal cells - contaminations

Question 24

how many single organisms must be cultures to diagnose UTI

Answer 24

> 10^5 CFU/mL with urinary symptoms

Question 25

different colours on chromogenic agar

Answer 25

pink = E.Coli
blue = other coliforms
light blue = gram positives

Question 26

which antibiotics are used to treat UTI

Answer 26

nitrofurantoin - EGFR must be >45ml/min
trimethoprim - if low risk of resistance
pregnant/ breastfeeding = cefalexin, co-amoxiclav (2nd line)
male = cefalexin, ciprofloxacin
pyelonephritis = co-amoxiclav +- gentamicin