2. Urinary tract infections

Question 1

Identify which pathogens commonly cause UTIs

Answer 1

*E.coli (gram neg)
*Proteus mirabilis (gram neg)
*S. saprophyticus (gram pos)
C. staphylococci
Schistosoma haematobium
T. vaginalis
Candida albicans

Question 2

Outline the signs and symptoms of UTIs:
Lower?
Infection of pelvis and kidney (acute pyelonephritis)?

Answer 2

Signs and symptoms:
• Lower UTIs:
– Frequency of micturition
– Urgency to urinate
– Dysuria
– Suprapubic pain & tenderness – Haematuria
– Smelly / cloudy urine
• Infection of pelvis and kidney (acute pyelonephritis): – Loin pain & tenderness
– High fever
– Systemic upset

Question 3

Aetiology of UTIs

Answer 3

• More common in women than men
• In men primarily >50 years of age
• Occurs in normal urinary tract
• Incidence 50,000 per million persons per year

Question 4

Which virulence factors are expressed by uropathogenic E.coli (UPEC)?

Answer 4

1. Fimbriae (For adhesion, Type 1 and Type P)
2. K antigen
   - Polysaccharide
   - Forms a micro-capsule
   - Confers resistance to phagocytosis
3. Haemolysin
   - Cytolytic exo-protein
   - Damages tissues membranes in vivo
   - Causes kidney damage

Question 5

What is the bacterial response to adhesion?

Answer 5

Iron acquisition machinery activated via siderophores
Stimulates growth and reproduction
Once a monolayer has formed a biofilm may develop
Bacteria with type 1 fimbriae may become internalised in phagocytes and epithelial cells.

Question 6

Features of proteus mirabilis as a causative agent of UTIs?

Answer 6

• Gram negative
• Facultative anaerobe
• Bacillus
• Peritrichous flagellae
• Produces urease
• Swarming ability

Question 7

Features of Staphylococcus saprophyticus as a causative agent for UTIs?

Answer 7

• Gram positive
• Coagulase negative
• Normal microbiota of female perineum & vagina
• Sexual activity increases risk of UTI
• Commonly causes community acquired UTIs
• Symptomatic cystitis

Question 8

Features of Candida albicans as a causative agent for UTIs?

Answer 8

• Diploid fungus (yeast)
• Commensal
• Candidiasis (thrush)
• Important opportunistic pathogen in immunocompromised individuals
• Often associated with antibiotic use

Question 9

Features of Trichomonas vaginalis as a causative agent for UTIs?

Answer 9

• Protozoan: Most common protozoal cause of UTIs
• Pear-shaped flagellate
• T. vaginalis is pathogenic
• Other species are commensal
• Prefers pH ~6.0
• Trichomoniasis
• Less common in males

Question 10

Features of Schistosoma haematobium as a causative agent for UTIs?

Answer 10

• Trematode worm
• Schistosomiasis (bilharzia)
• Found in contaminated water
• Gains access to host through skin
• Matures in liver
• Eggs travel to and penetrate bladder
• Treatment with praziquantal

Question 11

What are the 3 different types of urine specimens for lab analysis?

Answer 11

1. MSU (Mid-stream Specimen of Urine)
   - Significant bacteriuria
   - >10^5 per ml
2. CSU (Catheter Specimen of Urine)
   - Significant bacteriuria
   - Loer number of micro-organisms than MSU
3. Suprapubic aspiration of bladder urine
   - For schistosome haematobium and other rare occasions

Specimens used to perform urine dipstick test. (Nitrites present = infection)

Question 12

Urinary tract host defences?

Answer 12

• Urine - osmolality, pH
• Sloughing of epithelial cells
• Urine flow and micturition
• Mucosal inhibitors of bacterial adherence
• Complement activation
• Inflammatory response
• Immune responses
• Commensals

Question 13

What chemical is found in cranberry juice that helps to prevent E.coli adherence that leads to UTIs?

Answer 13

Proanthrocyanidins

Question 14

Oral Antibiotics for UTIs?

Answer 14

• Co-trimoxazole (good blind treatment)
• Nitrofurantoin
• Nalidixic acid
• Co-amoxiclav
• Trimethoprim
• Ciprofloxacin