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 5fluorouracil can have this effect. Some antibiotics do seem to pre-dispose to infection more than others eg: Clindamycin Cephalosporins, especially 3rd generation Antibiotic Erythromycin Clindamycin Ceftazidine Cefotaxime Weighted odds ratio (95% CL) 3.5 (2.1 – 5.8) 7.8 (3.8 – 16.1) 28.8 (12.7 – 65.1) 36.2 (19 - 68.9) 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 (3mg) Ampicilllin Cefuroxime Flucloxacillin Number of deaths on day 1 3 4 4/4 4/4 6/6 1/4 0/4 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 PMC High A(x3) S3 5 1 AAD Medium I 9 1 Animal Weak C 12 3 Infant Weak/none G, ?(x2) 1, 20, 26 Virulence factors of C. difficile 1. 2. 3. 4. 5. Toxins Adhesion Fimbriae Enzymes 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 Cytotoxicity Haemagglutination Increase vascular permeability Haemorrhage Fluid accumulation A + + + + + B + + + - Virulence factors of C. difficile 1. 2. 3. 4. 5. Toxins Adhesion Fimbriae Enzymes Capsule Virulence factors of C. difficile 1. 2. 3. 4. 5. Toxins Adhesion Fimbriae Enzymes Capsule Virulence factors of C. difficile 1. 2. 3. 4. 5. Toxins Adhesion Fimbriae Enzymes Capsule Virulence factors of C. difficile 1. 2. 3. 4. 5. Toxins Adhesion Fimbriae Enzymes 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