1. Lec. No. 11 Dr. Manahil Clostridium difficile C. difficile is a gram positive, spore forming, obligate anaerobe. Colonies of the organism are about 4mm in diameter on the selective medium cycloserine-sefoxitin fructose agar (CCFA). They are yellow and ground class-like and have filamentous edge. The odour associated with colonies is very distinctive and is typically like elephant or horse manure. C. difficile produces two toxins, an entero toxin (toxin A) and a cytotoxin (toxin B).

2. Pathogenicity C. difficile is part of the normal intestinal flora in a few number of healthy people and hospitalized patients. The disease develops in people taking antibiotics. The disease occurs if the organisms proliferate in the colon and produce their toxins. C. difficile cause the diseases antibiotic associated pseudomembranous colitis (APMC) and antibiotic associated diarrhoea (AAD). C. difficile is the most common cause of nosocomial diarrhoea.

3. Pathogenesis of C. difficile diarrhoea Antibiotic therapy Disruption of colonic microflora C.difficile exposure and colonization release of toxin A (enterotoxin) and toxin B (cytotoxin) mucosal injury and inflammation.

4. Antibiotic-related risk for C. difficile infection   High risk - Cephalosporins - Clindamycin.   Medium risk - Ampicillin / Amoxicillin - Tetracyclines - Marrolides - Co-trimoxazol   Low risk - Aminoglycosides - Rifampicin - Fluoroquinolones - Anti-pseudomonal penicillin ± -lactamse inhibitor.

5. Source of infection Patient – patient transmission of C. difficile strains. Faecal-oral route and hands of hospital personnel are important source for the infection. The microorganism can be cultured from swabs taken from different surfaces within the room in which the patient is reside. Hospitalized patients receiving internal tube feedings may be at increased risk for infection. Toilets, bedpans, hospital floors, scales, and furniture have all been identified as fomites for the spores of. C difficile.

6. Diarrheal disease I. Pseudomembranous colitis Diarrhoea starting within a few days of starting antibiotics, but antimicrobial therapy taken 1-2 months ago can still predispose to infection. Formation of microabscesses or pseudomembrane in patients who have such type of diarrhoea. The diarrhoea may be watery or bloody, and the patient has abdominal cramps, leukocytosis and fever.

7. II. Antiobiotic-associated diarrhoea The administration of antibiotics frequently leads to a mild- moderate form of diarrhoea termed antibiotic-associated diarrhoea. The disease less severe than pseudome-mbranous colitis. About 25% of cases of antibiotic associated diarrhoea due to C.difficile.

8. Immune response to C. difficile Only about half of the hospitalized patients develop diarrhoea following acquisition of C. difficile. Host immune response to C. difficile play a role in determining disease occurrance and recurrence. Antibodies against toxins A and B have been detected in the serum of about 70% of individuals. Patients who became asymptomatic carriers had significantly greater increases in serum immunoglobulin G (IgG) antitoxin.

9. Laboratory diagnosis 1. 1. The diagnosis of C. difficile infection is confirmed by demonstration of the enterotoxin or cytotoxin in a stool specimens. a- Cytotoxicity assay using tissue culture cells and specific neutralizing antibodies for the cytotoxin. b- Immunoassay for toxins in Stool by ELISA test which is more rapid. 2. 2. Isolation of the organism in anaerobic stool culture documents colonization but not disease. 3. 3. Endoscopy.

10. Epidemiology C. difficile is found as part of normal large bowel flora in about 2- 4% of normal young adults The rates of colonization in neonates (who have a less complex gut flora) may be very high (up to 70%). C. difficile isolated from animals as horses, cows, dogs and cats. Over 80% of C. difficile infection cases occur in hospitalized patients over 65 years old. In hospitals, the infected patients excretes more than 10 5 C. difficile per gram of stool. Environmental contamination with C. difficile have been demonstrated in 34-58% of sites in hospital wards. Other sources of C. difficile contamination include nurses blood pressure cuffs and thermometers.

11. Treatment Stop use of the implicated antibiotic mostly results in the resolution of the clinical symptoms. Oral vancomycin or metronidazole. Fluid replacement.