L4 - UTIs

Question 1

Are UTIs normally ascending or descending infections?

Answer 1

Ascending

Question 2

Are defences of UTIs almost entirely a consequence of INNATE or ADAPTIVE immunity?

Answer 2

Innate

Question 3

What 3 things defend against UTIs?

Answer 3

Urine
Urine flow - sheer force
Urinary tract mucosa

Question 4

How can urine defend against UTIs?

Answer 4

osmolarity - organism explode/shrivel

pH
organic acids
prostatic secretions (men)

Question 5

How can urinary tract mucosa defend against UTIs?

Answer 5

defensins (damage cell membrane)

antimicrobial peptides

glycosaminoglycan - restricts adherence

Tamm-Horsfall protein (inhibits fimbriae action)

IgA

Lactoferrin (iron sequestration)

Question 6

What are the 4 risk factors for UTIs?

Answer 6

Sex
Age
Structural abnormalities (retention)
Diabetes

Question 7

How is sex a risk factor for UTIs?

Answer 7

Women 50%, men 0.5%

pregnancy

anatomy of skin surrounding penis

location of urethra in men compared to woman where it is closer to anus

Question 8

How is age a risk factor for UTIs?

Answer 8

reduced expression of Tamm-Horsfall protein

prostatic hypertrophy - increasing retention

microbial changes in women - pH

Question 9

How are structural abnormalities a risk factor in UTIs?

Answer 9

urethral valves stopping expulsion of urine

vesicourtetal reflux

calculi (struvite stones)

Question 10

How is diabetes a risk factor?

Answer 10

glucose is source for bacteria

Question 11

What is the most common bacteria to cause UTIs?

Answer 11

E.coli - UPEC

Question 12

What agents cause COMMUNITY-ACQUIRED UTIs?

Answer 12

E.coli - 80%

proteus mirabilis - 6%

Question 13

What agents cause HOSPITAL PATIENT UTIs?

Answer 13

E.coli - 40%

(Klebsiella spp., Enterobacter, Serratia spp., P. aeruginosa) - 25%

Question 14

How can UTIs be caused in hospital patients?

Answer 14

Catheter introduces microorganisms

mechanical breaking of defence

purple bag syndrome

Question 15

What are the 3 different pathotypes

Answer 15

EHEC - enterohaemorrhagic
EPEC - Enteropathogenic
UPEC - Uropathogenic

Question 16

Pathogenesis of UPEC in the BLADDER

Answer 16

Adhesion - Type 1 pili
uroplakins, interns
IBCs
QIR

Question 17

Pathogenesis of UPEC in the KIDNEY?

Answer 17

Adhesion
Suppression of IgA secretion
P pili bind to TLR4 and prevent PIGR expression - stop import of immunoglobulin

Question 18

Pathogenesis of Proteus in the BLADDER?

Answer 18

introduced by catheterisation

urea turns to alkaline pH = crystals

struvite stones - crystalline biofilm
difficult to eradicate

Question 19

What are the 4 ways to collect urine for laboratory diagnosis?

Answer 19

Midstream urine

Catheter urine

Bag urine (bad method)

Supra-pubic aspirate

Question 20

What are the ways of diagnosing UTIs in the laboratory?

Answer 20

Dipstick
Microscopy
Flow cytometry
Laminar flow imaging

Question 21

How is culture good for laboratory diagnosis?

Answer 21

allows organism identification by:

• selective media
• Gram stain
• MALDI-TOF

Question 22

How can UTIs be treated?

Answer 22

Nitrofurantoin (B)

Trimethoprim-sulfamethoxazole (B)(K)

Fosfomycin (B)(K)

Fluoroquinolones (B)(K)

B-lactam antibiotics (B)(K)

aminoglycosides (K)

carbapenems (K)

Question 23

Prevention of UTIs?

Answer 23

Methenamine - formaldehyde in acidic urine

Restriction of spermicides in contraception

Topical oestrogen’s - revert to pre-menopausal microbiota

developing vaccines/anti-virulence agents