In-hospital anaerobic susceptibility testing: an aid to formulary decision making

In this study, the susceptibility of 116 recent anaerobic isolates, including the Bacteroides fragilis group (n = 22), Bacteroides spp (n = 65), gram-positive cocci (n = 13), Clostridium spp (n = 10), and Fusobacterium spp (n = 6) were tested by agar dilution against a variety of agents suggested for prophylaxis or therapy. These agents included ampicillin sodium and sulbactam sodium, cefotaxime, cefoxitin, ceftizoxime, clindamycin, imipenem-cilastatin, metronidazole, and ticarcillin and clavulanate potassium. All anaerobes demonstrated 100% susceptibility to imipenem-cilastatin, metronidazole, ampicillin sodium and sulbactam sodium, and ticarcillin and clavulate potassium. Varying degrees of susceptibility (ranging from 60% to 100%) of Bacteroides spp to the selected panel of antibiotics were seen. Fusobacterium spp and the gram-positive cocci were inhibited by all agents tested. Clostridium spp was 90% susceptible to cefoxitin, 80% susceptible to clindamycin, and 100% susceptible to the other six agents. Due to the varying activity of these agents, local susceptibility patterns, antimicrobic spectrum, and cost effectiveness must be considered in the choice of agents used for empiric therapy.