Clostridium difficile

Separating key facts from fiction

S P Borriello

16.5.08

1. Pathogenesis

- colonisation resistance

- virulence factors of C.difficile

2. Laboratory diagnosis

3. Treatment and Management

Why should we be interested?

1.It is the most common identifiable cause of nosocomial gut infection

2.It kills

3.It is preventable

PATHOGENESIS

A risk of infection with C. difficile follows antibiotic treatment and

exposure to C. difficile

This risk increases with age. The majority of cases are older

than 60 years.

Disease follows infection with toxigenic strains of C. difficile

and production of toxin in vivo.

Why is it that you need antibiotic treatment to make you susceptible to infection. It is due to the barrier

effect of the normal gut bacteria (colonisation resistance).

What antibiotics cause this disease?

All of them other than parenteral aminoglycosides.

Even chemotherapeutic agents eg 5-fluorouracil can have this effect.

Some antibiotics do seem to pre-dispose to infection more than others eg:

Clindamycin

Cephalosporins, especially 3rd generation

Antibiotic Weighted odds ratio

(95% CL)

Erythromycin 3.5 (2.1 – 5.8)

Clindamycin 7.8 (3.8 – 16.1)

Ceftazidine 28.8 (12.7 – 65.1)

Cefotaxime 36.2 (19 - 68.9)

C. Difficile is due to overgrowth of strains resistant

to the inciting antibiotic

NONO

In the animal model the biggest difference between antibiotics seems to be the length of time susceptibility

is induced.

Comparison of antibiotics in hamsters

Antibiotic Number of deaths on day

(3mg) 1 3 4

Ampicilllin 4/4 1/4 -

Cefuroxime 4/4 0/4 -

Flucloxacillin 6/6 7/8 2/8

C. difficile can cause a range of disease from mild diarrhoea

A number of factors could contribute to outcome of infection eg

Host factors

Degree of disruption of colonisation resistance

Virulence of the C. difficile strain

COMPARATIVE VIRULENCE OF C. DIFFICLE

No. of strains Source Virulence Serogroup Ribotype

5

1

1

3

PMC

AAD

Animal

Infant

High

Medium

Weak

Weak/none

A(x3) S3

I

C

G, ?(x2)

5

9

12

1, 20, 26

Virulence factors of C. difficile

1. Toxins

2. Adhesion

3. Fimbriae

4. Enzymes

5. Capsule

Both toxins A and B are the largest bacterial protein toxins known.

Toxin A 300 kDa

Toxin B 270 kDA

Effects of toxins A and B

A B

Cytotoxicity + +

Haemagglutination + -

Increase vascular permeability + +

Haemorrhage + +

Fluid accumulation + -

Virulence factors of C. difficile

1. Toxins

2. Adhesion

3. Fimbriae

4. Enzymes

5. Capsule

Virulence factors of C. difficile

1. Toxins

2. Adhesion

3. Fimbriae

4. Enzymes

5. Capsule

Virulence factors of C. difficile

1. Toxins

2. Adhesion

3. Fimbriae

4. Enzymes

5. Capsule

Virulence factors of C. difficile

1. Toxins

2. Adhesion

3. Fimbriae

4. Enzymes

5. Capsule

LABORATORY DIAGNOSIS

1. Do not investigate formed stools

2. Do not investigate infants under six months

Faecal cytotoxin is the gold standard.

Vero cells are the best choice cell line.

Kits are available for toxin A or toxin A and B.

Those that detect both are most sensitive.

There also exist toxin A-ve B+ve strains which cause diseases.

Toxin A kits miss these.

Culture is best achieved by growth on a selective medium incorporating cyloserine (250mg/l) and cefoxatin (8mg/l).

Colonies fluoresce under long wave UV light.

Alcohol (1 : 1 ratio) or heat (75˚c 20 mins) can be used to select for spores as an alternative isolation procedure.

CONTROL / PREVENTION

1. Limit antimicrobial use

2. Good infection control

- Hand washing

- Enteric precautions

- Clean environment

Decontamination must remove spores

Decontamination

Hospital Surfaces: Routine cleaning

Equipment: 2% alkaline buffered glutaraldehyde

TREATMENT OF CASES (Conventional)

Stop the precipitating antibiotics (15-25% success)

Vancomycin 125mg qds 7-10 days

OR

Metronidazole 400mg tds 7-10 days

TREATMENT OF CASES (Unconventional)

1. Faecal enemas / faecal flora cocktails

2. Probiotics

- lactobacilli- Saccharomyces boulardii

3. Non-toxigenic C. difficile