Metronidazole and vancomycin are equally effective in the treatment of Clostridium difficile infection, according to data presented at the 51st Interscience Conference on Antimicrobial Agents and Chemotherapy in Chicago. Metronidazole and vancomycin were equivalent in the treatment of C. difficile infection irrespective of the severity of illness (P=0.14) according to the results of a study presented by Qamar Saleheen, MD, of the Hines VA Hospital in Hines, Illinois, and colleagues. The study demonstrated no difference in mortality between patients treated with either of these antibiotics. There was also no difference in either the rate of recurrence between metronidazole and vancomycin groups (P=0.41) or the rate of complications between the two groups (P=0.77). In this retrospective study, Dr. Saleheen and colleagues reviewed the records of 152 inpatients and outpatients with C. difficile infections. Of these patients, 147 (145 male, 2 female) were included in the study: 25 initially received oral vancomycin and 122 initially received metronidazole. Of the 122 patients who initially received metronidazole, 28 received cross over treatment with oral vancomycin. C. difficile is a cause of antibiotic associated diarrhea and is common in hospitalized and nursing home patients as well as patients over the age of 65. The Society for Healthcare Epidemiology of America (SHEA) published treatment guidelines in May 2010 recommending the use of metronidazole for the treatment of mild to moderate illness and the use of vancomycin for the treatment of severe illness. Dr. Salaheen noted that vancomycin is much more expensive than metronidazole and, according to the results of his study, the use of the more expensive antibiotic may not be justified. The authors did note, however, that the study was limited by its small population size.