Clostridium difficile

A patient on the intensive care unit develops offensive diarrhoea following treatment for ventilator-associated pneumonia. Clostridium difficile toxin has been detected in the stool. Which one of the following statements regarding C. difficile infection is TRUE?

a) Following initial treatment of C. difficile colitis recurrence is uncommon

b) Over 50% of adults carry C. difficile asymptomatically

c) The pathogenesis of C. difficile is secondary to the production of two types of

exotoxin

d) Treatment with broad spectrum cephalosporins carries the highest risk of developing C. difficile colitis compared with treatment with other antibiotic types or groups

e) Non-toxin producing strains of C. difficile may cause pseudomembranous colitis

Answer: c

Explanation

C. difficile is a Gram-positive anaerobic bacillus, so named because originally it was a ‘difficult’ organism to isolate and culture. It is a normal commensal in up to 5% of the adult population and upto 50% of infants. In the latter, resistance to C. difficile colitis is thought to be secondary to the immaturity of an infant’s enterocyte membrane toxin receptors. Hospitalised patients are at highest risk of C. difficile colitis because they often receive broad spectrum antibiotics in an environment where contamination with C. difficile spores is commonplace. These spores may survive for years in the environment. Broad spectrum cephalosporins and penicillins are the most commonly implicated antibiotics due to the number of prescriptions, but clindamycin is the most likely to cause C. difficile colitis. The pathogenic C. difficile organisms are those that produce toxins of which there are two: toxin A and toxin B. Outbreaks of C. difficile 027 are of particular concern because this particular strain produces much more of the toxins than most other types because a mutation has

knocked out the gene that normally restricts toxin production. The colitis caused by the toxins may occur with or without pseudomembrane formation. Treatment is supportive along with discontinuation of any implicated antibiotics and commencement of metronidazole or vancomycin. Colonic resection is sometimes indicated in the most severe cases.

Reference

Kelly CP, LaMont JT. Clostridium difficile – more difficult than ever. New Engl J Med

2008; 359(18):1932–40.