COMPARISON OF DISC DIFFUSION AND AGAR DILUTION METHODS FOR ANTIBIOTICSUSCEPTIBILITY TESTING OF CAMPYLOBACTER-JEJUNI SUBSP JEJUNI AND CAMPYLOBACTER-COLI

The correlation between disc diffusion and agar dilution susceptibilit y testing of five antibiotics was studied against 145 Campylobacter st rains: 99 Campylobacter jejuni subsp, jejuni and 46 Campylobacter coli . The percentages of true results and 95% CI for disc diffusion for re sistant strains were 100% (93.2-100%) for tetracycline (53 strains tes ted), 100% (77.2-100%) for ciprofloxacin (13 strains tested), 86.7% (6 2.1-96.3%) for nalidixic acid (15 strains tested), 100% (56.6-100%) fo r erythromycin (five strains tested) and 68.8% (44.4-85.8%) for ampici llin (16 strains tested). The percentages of true results and 95% CI w ere 97.6-100% and 93.2-100% respectively for 89-140 susceptible strain s to the five antibiotics tested. There was a 1.4% major error for nal idixic acid, 0.7% very major error for erythromycin, 5.5% and 1.4% min or and major errors respectively for ampicillin. There was complete ag reement for ciprofloxacin and tetracycline. Results of ampicillin susc eptibility are not expected to be useful in a clinical setting. The na lidixic acid disc is a marker of ciprofloxacin susceptibility as the n alidixic acid-susceptible strains were susceptible to ciprofloxacin wh ile most of the resistant ones were resistant to ciprofloxacin. Overal l, our results suggest that disc diffusion is a reliable, easy and ine xpensive susceptibility testing method for C. jejuni and C. coli for e rythromycin, ciprofloxacin and tetracycline. Until more erythromycin- and ciprofloxacin-resistant strains are tested to confirm the reliabil ity of this test, the resistance to these drugs needs to be confirmed using the Etest or the agar dilution method.