Microbiology of the Urinary Tract

Question 2

What are the main routes of UTI acquisition?

Answer 2

Ascending (from urethra to bladder/kidney) and haematogenous (from blood to kidney).

Question 3

What are the main sites of UTI?

Answer 3

Urethra (urethritis), bladder (cystitis), kidney (pyelonephritis).

Question 4

What’s the difference between community-acquired and nosocomial UTI?

Answer 4

Community-acquired occurs outside healthcare settings; nosocomial occurs during hospitalisation, often catheter-related.

Question 5

How common are UTIs in women?

Answer 5

5% of women present to GPs annually; up to 50% experience one in their lifetime.

Question 6

What is the most common cause of UTI?

Answer 6

Uropathogenic E. coli (UPEC), a normal flora of the large bowel.

Question 7

Name other infectious causes of UTI besides E. coli.

Answer 7

Adenoviruses, BK/JC viruses (post-transplant), Mycobacterium tuberculosis, Schistosoma haematobium.

Question 8

Name 4 host defences against UTI.

Answer 8

• Urine flow/micturition
• Urine chemistry (pH, osmolality)
• Secreted factors: sIgA, lactoferrin
• Mucosal defences: mucopolysaccharides, low receptor density

Question 9

What are Type 1 fimbriae?

Answer 9

E. coli structures that bind to mannose residues, associated with cystitis (lower UTI).

Question 10

What are Type P fimbriae and K antigens?

Answer 10

Type P fimbriae bind to kidney cells; K antigen inhibits phagocytosis—both linked to pyelonephritis.

Question 11

What are risks of UTI during pregnancy?

Answer 11

Low birth weight, premature delivery, perinatal morbidity, pyelonephritis (30% of untreated cases).

Question 12

Symptoms of cystitis in pregnancy?

Answer 12

Frequency, urgency, dysuria, suprapubic discomfort, mild/no fever.

Question 13

Symptoms of pyelonephritis?

Answer 13

Cystitis symptoms + loin pain, fever, rigors, renal angle tenderness.

Question 14

What does urinalysis detect in UTI?

Answer 14

Protein, blood, leukocyte esterase, nitrites.

Question 15

What can cause false negatives in urinalysis?

Answer 15

Antibiotics, low bacteria count, high glucose, non-nitrate-reducing bacteria.

Question 16

What suggests contamination in urine microscopy?

Answer 16

Presence of epithelial cells.

Question 17

What is the most common nosocomial infection?

Answer 17

Catheter-associated UTI.

Question 18

How do catheters increase UTI risk?

Answer 18

Bypass defences, act as foreign bodies, allow biofilm formation.

Question 19

Catheter-associated UTI: What works to prevent it?

Answer 19

Aseptic insertion, limiting duration, closed drainage, silver-bonded catheters.

Question 20

What does NOT help prevent catheter-associated UTI?

Answer 20

Soap at meatus, bladder irrigation with antiseptics.

Question 21

What is urethral syndrome?

Answer 21

UTI symptoms with negative cultures, often due to fastidious organisms or non-infectious causes.

Question 22

First-line management of uncomplicated lower UTI?

Answer 22

Hydration; may resolve spontaneously. If antibiotics needed: short 3-day course.

Question 23

Why use short antibiotic courses for UTI?

Answer 23

Reduce resistance, fewer side effects, as effective as longer courses.

Question 24

When is antimicrobial prophylaxis considered in women?

Answer 24

If >3 UTIs annually.

Question 25

When should a urine sample be sent in children?

Answer 25

If fever >38°C for >24 hours.

Question 26

What are UTI risk factors in children?

Answer 26

Poor flow, recurrent fever, renal abnormalities, VUR, constipation, poor growth, high BP, etc.

Question 27

How is UTI diagnosed in children <3 months?

Answer 27

Less reliance on dipsticks; follow NICE CG160 guidance.

Question 28

Antibiotics for lower tract UTI in children?

Answer 28

Amoxicillin, trimethoprim, cephalexin.

Question 29

Antibiotics for upper tract UTI (mild)?

Answer 29

Co-amoxiclav.

Question 30

Antibiotics for upper tract UTI (severe)?

Answer 30

Cefotaxime or gentamicin.

Question 31

Why is E. coli the most common cause of UTI?

Answer 31

It's part of normal bowel flora and has specific virulence factors that promote UTI.

Question 32

When should catheter-associated bacteriuria be treated?

Answer 32

Only if symptomatic.

Question 33

What does a high number of white cells in urine microscopy suggest?

Answer 33

Infection (presence of pyuria).

Question 34

What does a high number of epithelial cells in urine suggest?

Answer 34

Contamination of the urine sample.

Question 35

What are causes of red blood cells in urine?

Answer 35

Menstruation, infection, stones, tumours.

Question 36

Why does nitrite have low sensitivity in urinalysis?

Answer 36

Not all bacteria reduce nitrate to nitrite; low bacterial count may also cause false negatives.

Question 37

What does leukocyte esterase detect?

Answer 37

Presence of neutrophils (indirect evidence of infection).

Question 38

How fast does bacteriuria develop in catheterised patients?

Answer 38

Increases by 5–10% for each day the catheter remains in place.

Question 39

Should asymptomatic catheter-associated bacteriuria be treated?

Answer 39

No, only if patient is symptomatic.

Question 40

What is a key method to reduce CAUTI?

Answer 40

Avoid unnecessary catheterisation and remove promptly.

Question 41

What percentage of women with cystitis symptoms have negative cultures?

Answer 41

Up to 50%.

Question 42

What are possible causes of urethral syndrome?

Answer 42

- Low bacterial count - Fastidious organisms (e.g., Ureaplasma) - Non-infective inflammation - STIs like Chlamydia trachomatis

Question 43

What is considered recurrent UTI?

Answer 43

≥3 episodes per year.

Question 44

Management strategies for recurrent UTI?

Answer 44

- Antimicrobial prophylaxis - Self-start antibiotics - Voiding post-intercourse - Vaginal HRT in postmenopausal women

Question 45

Role of cranberry in UTI prevention?

Answer 45

Limited evidence; Cochrane review (2008) showed weak benefit only in young women.

Question 46

What diagnostic method is recommended for children <3 months with fever?

Answer 46

Urine sample + treat as per NICE CG160 guidelines.

Question 47

Why is imaging important in children with UTI?

Answer 47

To detect underlying renal tract abnormalities (e.g., VUR, obstruction).

Question 48

Name 5 risk factors for UTI in children.

Answer 48

- Recurrent fever - Poor urine flow - Constipation - Family history of renal disease - History of UTI (others: VUR, spinal lesions, poor growth, high BP)

Question 49

Why are antibiotics with high urinary concentration preferred?

Answer 49

They ensure effective eradication of urinary pathogens.

Question 50

What makes uropathogenic E. coli (UPEC) unique?

Answer 50

- Type 1 fimbriae: bind to mannose (cystitis) - P fimbriae: bind to kidney cells (pyelonephritis) - K antigen: inhibits phagocytosis

Question 51

Classic triad of cystitis symptoms?

Answer 51

Frequency, urgency, dysuria.

Question 52

Key symptoms of pyelonephritis?

Answer 52

Fever, loin pain, rigors, possible nausea/vomiting.

Question 53

When is fever absent in UTI?

Answer 53

Often in lower UTI/cystitis.

Question 54

How often do healthy women urinate per day on average?

Answer 54

3.4 times/day.