Clostridium difficile Separating key facts from fiction S P Borriello

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 3 rd generation

Antibiotic Weighted odds ratio (95% CL) Erythromycin3.5 (2.1 – 5.8) Clindamycin7.8 (3.8 – 16.1) Ceftazidine28.8 (12.7 – 65.1) Cefotaxime36.2 ( )

C. Difficile is due to overgrowth of strains resistant to the inciting antibiotic NO

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)134 Ampicilllin4/41/4- Cefuroxime4/40/4- Flucloxacillin6/67/82/8

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 strainsSourceVirulenceSerogroupRibotype PMC AAD Animal Infant High Medium Weak Weak/none A(x3) S3 I C G, ?(x2) , 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 B270 kDA

Effects of toxins A and B AB 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