Microbio - UTIs

Question 1

Define bacteriuria and cystitis

Answer 1

Bacteriuria = presence of bacteria in the urine

Cystitis = inflammation of the bladder, often caused by infection

Question 2

What is the relevance of asymptomatic bacteriuria

Answer 2

Asymptomatic bacteriuria is usually not relevant (due to colonisation)

It is relevant in PREGNANCY or CHILDREN

Question 3

What is the difference between uncomplicated and complicated cystitis

Answer 3

Uncomplicated: infection is a structurally and neurologically normal urinary tract

Complicated: infection with functional or structural abnormalities (including indwelling catheters and calculi)

Question 4

What is a sign that an MSU sample has not been taken properly

Answer 4

Squamous epithelial cells found in the urine (usually at the end of the urethra)

Question 5

What factors would be regarded as a complicated UTI

Answer 5

Men
Pregnant women
Children (not young girls) - concerns about renal scarring or structural abnormalities
Patients in a healthcare- or HC-associated settings

Question 6

What % of women will experience a symptomatic UTI at some point in life

Answer 6

40-50%

Question 7

What is the most common causative organism for cystitis and why

Answer 7

Escherichia coli (O1, O2, O4, O6, O7, O8, O75, O150, O18ab)
They have adherence factors that allow prevention of flushing out by urine
Virulence factor expression is greater among the above groups → allows for more severe infection

Question 8

What organisms can cause UTI

Answer 8

E. Coli
Staphylococcus saprophyticus (Virulence factors (P-fimbriae) that allow adherence to the epithelium)
Proteus mirabilis (kidney stones)
Klebsiella aerogenes (prosthetic materials e.g. stents, catheters)
Enterococcus faecalis
Staphylococcus epidermidis (prosthesis e.g. procedures or long-term indwelling catheter)

Question 9

What are the risks of recurrent UTI

Answer 9

Renal scarring
Non-E. Coli organism infection e.g. Proteus, Pseudomonas, Klebsiella and Enterobacter and enterococci and staphylococci

Question 10

What are the Antibacterial Host Defences in the Urinary Tract

Answer 10

Urine (osmolality, pH, organic acids)
Urine flow and micturition
Urinary tract mucosa (bactericidal activity, cytokines)

Question 11

Why are UTIs more common in women

Answer 11

Female urethra is short and in proximity to the vulvar and perianal areas, making contamination likely (more common in women)
Massage of the urethra and sexual intercourse can force bacterial into the female bladder

I.E. organisms that cause UTI in women colonise the vaginal introitus and the periurethral area prior to UTI

Question 12

Why can cystitis progress into pyelonephritis

Answer 12

Once in the bladder, bacteria multiply and pass up the ureters (especially in the presence of vesicoureteric reflux or prosthetic material) to the renal pelvis and parenchyma  pyelonephritis

Question 13

What are the causes of renal tract obstruction

Answer 13

• Mechanical
  
  • Extrarenal:
    ○ Valves, stenosis or bands
    ○ Calculi
    ○ BPH
  • Intrarenal
    ○ Nephrocalcinosis
    ○ Uric acid nephropathy
    ○ Analgesic nephropathy
    ○ PKD
    ○ Hypokalaemic nephropathy
    ○ Renal lesions of SCD
  • Neurogenic malfunction:
    ○ Poliomyelitis
    ○ Tabes dorsalis
    ○ Diabetic neuropathy
    ○ Spinal cord injuries

Question 14

Describe the haematogenous route of UTI

Answer 14

Kidney is a frequent site of abscesses in patients with S. aureus bacteraemia or endocarditis -> excretion of Staph aureus into the urine

S. aureus does NOT have appropriate virulence factors to cause ascending infection - I.E. if you see S. aureus in the urine, it is much more likely to have come from a bacteraemia

Question 15

What are the symptoms of UTI in children

Answer 15

<2: non-specific e.g. failure to thrive, vomiting, fever

> 2: frequency, dysuria, abdominal/flank pain

Question 16

What are the symptoms of a lower UTI

Answer 16

Bacteria → irritation of urethral & vesical mucosa → frequent/painful urination of small amounts of turbid urine

Suprapubic heaviness or pain
Gross haematuria
Fever absent (in infections confined to lower UT)

Question 17

What are the symptoms of upper UTI

Answer 17

Lower UT symptoms / LUTS [frequency, urgency, nocturia, dysuria] / FUND HIPS
* May precede UUTS by 1-2 days
* Symptoms may vary greatly
Fever (sometimes with rigors)
Flank pain

Question 18

What are the symptoms of UTI in elderly patients

Answer 18

Vast majority will be ASYMPTOMATIC
Symptoms of upper urinary tract infections are often atypical (e.g. abdominal pain, confusion)
Diagnosis difficult as non-infected older patients often experience frequency, dysuria, hesitancy & incontinence

Question 19

What investigations should be done for suspected UTI

Answer 19

Urine dipstick: Nitrites (Produced by gram -ve) and Leukocyte esterase (inflammation)

MSU for urine MC&S BEFORE antibiotics administration (bottle for this contains boric acid, red top) - not useful in adults >65

Bloods – FBC, U&E, CRP

Complicated → renal USS< IV urography

Question 20

What does the presence of +++ Nitrites in the urine suggest

Answer 20

E. Coli infection

Question 21

What does nitrite -ve, LE +ve dipstick suggest

Answer 21

Non-coliform bacteria i.e. NOT E. coli

Question 22

When should MC&S of urine be done

Answer 22

Pregnancy (because asymptomatic bacteriuria is an issue)
Suspected UTI in children
Suspected UTI in men
Suspected pyelonephritis
Catheterised patients
Failed antibiotic treatment (resistance)
Abnormalities of the genitourinary tract
Renal impairment
>65yo if symptomatic

Question 23

What results from culture will diagnose UTI

Answer 23

Culture of single organisms >10^5 CFUs/mL + urinary symptoms
Culture of E. coli or S. saprophyticus organisms >10^3 CFUs/mL + urinary symptoms

Question 24

What does mixed growth from culture suggest

Answer 24

Contamination

Question 25

What should be considered in sterile pyuria (raised WCC, no growth)

Answer 25

Prior treatment with antibiotics (MOST COMMON)
Calculi
Catheterisation
Bladder neoplasm
TB
STI (Chlamydia trachomatis)

Question 26

What do the colours pink, blue and light blue suggest on culture for UTI

Answer 26

Pink: E. coli
Blue: other coliforms
Light blue: gram +ve

Question 27

What are the methods for urine sampling

Answer 27

Urine in the bladder is normally sterile. Because the urethra and periurethral areas are very difficult to sterilise, even the most carefully collected specimens (including those obtained by catheterisation) are frequently contaminated.
* MSU (best method)
* Catheterisation (may introduce organisms)
* Suprapubic aspiration (sometimes used in very young children)

Question 28

What is the management of UTIs

Answer 28

1. Send MSU before Abx
2. Start empirical therapy - usually trimethoprim, nitrofurantoin, cephalexin

3 days of therapy with standard doses for treatment of uncomplicated lower urinary tract infection in women

Question 29

When is short course therapy for UTI not indicated and how long should therapy be for them

Answer 29

History of previous urinary tract infection caused by antibiotic-resistant organisms
>7 days of symptoms
Men

7 days of treatment

Question 30

What is a risk factor for canididal UTI and how is it managed

Answer 30

Indwelling catheter

1. Remove catheter
2. No treatment (unless renal transplant or waiting for surgery)

Question 31

What is the difference in vulnerability to infection of different parts of the kidney

Answer 31

Few organisms are needed to infect the renal medulla
Many organisms are needed to infect the cortex

Question 32

What is the management for pyelonephritis

Answer 32

Prior to culture results → amoxicillin (or ciprofloxacin)
Culture results → co-amoxiclav ± gentamicin (broad spectrums)

Question 33

What are the complications of pyelonephritis

Answer 33

Perinephric abscess
Chronic pyelonephritis  scarring, chronic renal impairment (mainly seen in children, treated more aggressively)
Septic shock
Acute papillary necrosis