In-vitro evaluation of carumonam (Ro 17-2301)

The in-vitro antibacterial activity of carumonam (Ro 17-2301) was assessed and compared with those of aztreonam and other beta-lactam antibiotics. Carumonam was highly active against the Enterobacteriaceae and Pseudomonas strains resistant to ampicillin (MIC greater than or equal to 256 mg/l) and carbenicillin (MIC greater than or equal to 64 mg/l), respectively. The MICs of carumonam for 90% of the strains ranged between 0.25 mg/l for Klebsiella spp. to 32 mg/l for Pseudomonas spp. The antibacterial activity was minimally altered by changes of medium or inoculum size. Carumonam was resistant to hydrolysis by the plasmid-mediated and chromosomal beta-lactamases tested. Also in the microbiological assay no inactivation was observed. Carumonam was an effective inhibitor of the SHV enzyme and the chromosomal beta-lactamases tested. Against the other plasmid-mediated enzymes carumonam was not an effective inhibitor.