UPDATE ON CLOSTRIDIUM DIFFICILE-INDUCED COLITIS .2.

Clostridium difficile is a nosocomial pathogen able to survive unfavorable environments by sporulation; when conditions advantageous for rapid growth appear, the vegetative form is regenerated. Lack of conscientious hand washing and failure of health care providers to use disposable gloves facilitate transmission within institutions. Exposure to certain antimicrobials expedites C. difficile overgrowth within the colon by altering the composition of the normal gut microflora. Antineoplastic agents may also precipitate CDIC. The characteristics of the colonizing strain, the properties of the inciting drug, and individual host factors collectively seem to govern the expression of the disorder. Clinical presentations range from self-limiting diarrhea to severe diarrhea accompanied by abdominal pain, fever, and leukocytosis to potentially life-threatening PMC. A preponderance of data supports the interpretation that oral metronidazole and oral vancomycin are therapeutically equivalent for the treatment of all but the most severe cases of CDIC. Whether the two drugs are equivalent in severe CDIC is controversial and will probably remain so in the absence of a well- designed trial to expand on the findings of the study by Teasley et al. Because of the cost difference and therapeutic equivalence, oral metronidazole should be the preferred routine treatment for CDIC; oral vancomycin should be reserved for severe cases and cases that fail to respond to at least six days of oral metronidazole therapy. Another important argument, albeit a hypothetical one, for limiting institutional use of oral vancomycin is to minimize selective environmental pressure for the emergence and dissemination of vancomycin-resistant enterococci. An epidemic outbreak of CDIC caused by clindamycin-resistant C. difficile in an institution where clindamycin use was extremely high illustrates the possible consequences of such selective pressure. Oral metronidazole 250 mg four times daily will usually provide a satisfactory response, but clinicians may wish to consider increasing the total daily dose for some patients who have symptoms like fever and leukocytosis. For oral vancomycin, 125 mg four times daily is sufficient in virtually all circumstances. Ten days of therapy is usually adequate for either drug. CDIC in a patient unable to take medications orally presents a bit of a therapeutic dilemma. Two approaches that appear effective are rectal administration of vancomycin and intravenous administration of metronidazole, although intravenous metronidazole can fail to work, possibly because the colonic concentrations achieved are inadequate. Clinicians may wish to consider a total daily dose of intravenous metronidazole that is at the upper end of the adult dosage range, if this is feasible. Many approaches to treating recurrent CDIC have been described, but none has been proved superior. If antimicrobial retreatment is chosen, there is no evidence to suggest that switching from metronidazole to vancomycin will improve the outcome. Current understanding of the pathophysiology of CDIC mandates that any approach selected should limit antimicrobial exposure to the greatest extent possible in order to allow the normal colonic microflora to become reestablished. Asymptomatic carriers of C. difficile should not be treated with antimicrobials. Watchful waiting accompanied by supportive care has been underemphasized as a response to mild CDIC, both initially and for a first relapse. Resisting the temptation to treat every symptomatic patient with antimicrobials may well reduce the number of patients with recurrent CDIC, particularly those who suffer multiple relapses. A study directly addressing this issue would be helpful. Of the investigational treatments for CDIC, the tiacumicin macrolides and the yeast Saccharomyces boulardii appear most promising. Application of the polymerase chain reaction to the diagnosis of CDIC may ultimately allow more specifically targeted and more timely therapeutic intervention. Avoidance of unnecessary cases of CDIC will almost certainly help lower health care expenses. According to Pear et al., a single episode of CDIC can add $2000-$5000 to the cost of a hospital stay.