August 15, 2012

Patient with suspected Pseudomembranous colitis

A patient suffering from suspected Pseudomembranous colitis is treated with metronidazole. The role of metronidazole in eradicating the causative organism is to:

a) cleave bacterial DNA
b) dissolve the pseudomembranes
c) disrupt bacterial mitochondrial function
d) compete with broad spectrum antibiotics
e) this statement is false, metronidazole is contraindicated in suspected Pseudomembranous colitis

The correct answer is A

Pseudomembranous colitis or antibiotic-induced colitis is acute diarrheal disease caused by Clostridium difficle. It is associated with the use of broad spectrum antibiotics especially ampicillin, lincomycin, clindamycin, cephalosporins etc.

The broad spectrum antibiotics cause the destruction of the normal bacterial flora in the gut which results in the overgrowth of Clostridium difficle which is resistant to most of these antibiotics. Clostridium difficle is an anaerobic bacteria. Due to its anaerobic character it is resistant to all the usual antibiotics.

The drug of choice is Metronidazole which is the most effective antibiotic for all anaerobic infections. Reduced metronidazole, which is cytotoxic but short-lived, interacts with DNA to cause a loss of helical structure, strand breakage, and resultant inhibition of nucleic acid synthesis and cell death in the anaerobic bacteria.

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