Empyema due to Bacteroides gracilis: case report and in vitro susceptibilities to eight antimicrobial agents

We describe a patient with empyema due to Bacteroides gracilis and a viridans streptococcus. Therapy with both cefoxitin and imipenem failed, and the patient remained symptomatic even after thoracotomy was performed. Clinical response occurred after initiation of clindamycin therapy. The susceptibilities of the patient's isolate, other clinical strains, and the reference strain were determined by an agar dilution method. The isolates were generally susceptible to all the agents tested; however, some strains were resistant to clindamycin (MIC, 8 micrograms/mL), penicillin G (MIC90, 16 micrograms/mL), and metronidazole (MIC90, 64 micrograms/mL). The B. gracilis isolate from our patient was susceptible to all agents tested, including cefoxitin and imipenem.