Antimicrobial susceptibility of Campylobacter fetus subsp. fetus isolated from blood and synovial fluid

Campylobacter fetus subsp. fetus is a rare human pathogen, but can cause serious extraintestinal infections. Effective antimicrobial agent is required for the therapy, but we have very limited knowledge on the susceptibility of the organism. In this study, the susceptibility of 25 isolates of the organism to 14 antimicrobial agents was tested by an agar dilution method. Antimicrobial agents with low MIC ranges, in μg/ml, were meropenem ≤ 0.25, dirithromycin ≤ 0.5, gentamicin ≤ 1, amikacin, ofloxacin, tetracycline and erythromycin ≤ 2. The MIC range of cefepime was 0.5-8 μg/ml, but those of other β-lactams were relatively high. All of the isolates were interpreted to be susceptible to cefepime, meropenem, amikacin, gentamicin, ofloxacin, tetracycline and dirithromycin. A significant proportion, of the isolates were either intermediate or resistant to ampicillin, cephalothin, cefotaxime, aztreonam, loracarbef and erythromycin. In conclusion, the organism remains susceptible to aminoglycosides and tetracycline. Greater in vitro activity of meropenem, ofloxacin and dirithromycin require clinical evaluation.