Antianaerobe activity of ceftobiprole, a new broad-spectrum cephalosporin

Agar dilution testing of 463 anaerobes showed most Gram-positive β-lactamase–negative strains (other than some Clostridium difficile and Peptostreptococcus anaerobius), as well as both β-lactamase–positive and β-lactamase–negative strains of Fusobacterium nucleatum, to have ceftobiprole MIC values of ≤0.016 to 4 μg/mL. Ceftobiprole was less active against β-lactamase–positive Gram-negative bacilli, especially the members of the Bacteroides fragilis group. Like ceftobiprole, piperacillin was active mainly against β-lactamase–negative strains, though MIC values for piperacillin were often 1 to 2 dilutions higher than for ceftobiprole. Carbapenems had MIC values ≤4 μg/L against all except some C. difficile and 2 strains of B. fragilis. All strains were susceptible to metronidazole, and all bacteria, except C. difficile and a single Bacteroides distasonis strain, were susceptible to chloramphenicol. Clindamycin resistance was seen in most anaerobe groups, whereas high moxifloxacin MICs were found mainly among the B. fragilis and Prevotella groups, and a few C. difficile and F. nucleatum strains.