Susceptibility of related vibrios and Vibrio fetus to twelve antibiotics.

One hundred fourteen strains of related vibrio and seven strains of Vibrio fetus, all isolated from humans, were tested for susceptibility in vitro to 12 antibiotics. Mueller-Hinton agar containing 14 dilutions of the antibiotics was inoculated with undiluted overnight cultures. Gentamicin and erythromycin were the most active drugs against related vibrios and Vibrio fetus; lower activity was noted with chloramphenicol, streptomycin, and tetracycline; neomycin and kanamycin were even less active. The susceptibility to ampicillin was variable. More than 90% of the strains were resistant to cephalothin.