Antibiotic susceptibilities of human isolates of Pasteurella multocida.

Seventeen human strains of Pasteurella multocida, biochemically similar to, if not identical with, isolates of animal origins, were tested for susceptibility to 16 antimicrobial agents utilizing a microtiter broth dilution technique. Ten of these isolates were also tested against 11 antibiotics by disk diffusion. The most active drugs with respect to the median minimal inhibitory concentration (micrograms per milliliter) were tetracycline (0.09), penicillin G (0.78), ampicillin (0.78), carbenicillin (1.56), cephalothin (1.56), and chloramphenicol (1.56). With the exception of tetracycline, the median minimal inhibitory concentration and minimal bactericidal concentration values were equal or differed by no more than a factor of two. The semisynthetic penicillins clindamycin, erythromycin, and aminoglycosides had relatively low activities, suggesting that these agents would be poor choices for the treatment of P. multocida infections.