[Bacterial combination effect between carumonam and eight other antibiotics]

In vitro interactions between carumonam (CRMN) and 8 other antibiotics were studied using the agar dilution checkerboard technique against 88 clinical isolates of Escherichia coli, Proteus vulgaris, Serratia marcescens and Pseudomonas aeruginosa. Combinations of CRMN with 8 other antibiotics were generally additive or indifferent. Synergism was found against S. marcescens or P. aeruginosa with CRMN plus fosfomycin, gentamicin (GM) or dibekacin. Antagonism was not observed with CRMN plus any of the 8 other antibiotics tested. In a phase-contrast microscopic study, the synergism of CRMN in combination with GM were confirmed against P. aeruginosa 15846. CRMN in combination with GM demonstrated a in vivo synergy against experimental urinary tract infection caused by P. aeruginosa 15846 in mice. We think that combinations of several antibiotics with CRMN should be appropriate for initial therapy of infections because no antagonism appeared to occur with other antibiotic agents.