Susceptibility of Campylobacter fetus to twenty-two antimicrobial agents.

In vitro susceptibility of 11 recent clinical isolates of Campylobacter fetus to 22 antimicrobial agents was determined by an agar dilution technique. Unlike most obligate anaerobic gram-negative bacilli, C. fetus isolates tested were relatively resistant to penicillin and cephalosporins, but exquisitely susceptible to tetracyclines and aminoglycosides. All strains were also inhibited at concentrations achievable in serum by clindamycin, chloramphenicol, metronidazole, carbenicillin, ticarcillin, and with rare exceptions, ampicillin. They were variably susceptible to lincomycin and erythromycin and highly resistant to vancomycin.