title: Comparison of disc diffusion and agar dilution methods for antibiotic susceptibility testing of Campylobacter jejuni subsp. jejuni and Campylobacter coli.
abstract: The correlation between disc diffusion and agar dilution susceptibility testing of five antibiotics was studied against 145 Campylobacter strains: 99 Campylobacter jejuni subsp. jejuni and 46 Campylobacter coli. The percentages of true results and 95% CI for disc diffusion for resistant strains were 100% (93.2-100%) for tetracycline (53 strains tested), 100% (77.2-100%) for ciprofloxacin (13 strains tested), 86.7% (62.1-96.3%) for nalidixic acid (15 strains tested), 100% (56.6-100%) for erythromycin (five strains tested) and 68.8% (44.4-85.8%) for ampicillin (16 strains tested). The percentages of true results and 95% CI were 97.6-100% and 93.2-100% respectively for 89-140 susceptible strains to the five antibiotics tested. There was a 1.4% major error for nalidixic acid, 0.7% very major error for erythromycin, 5.5% and 1.4% minor and major errors respectively for ampicillin. There was complete agreement for ciprofloxacin and tetracycline. Results of ampicillin susceptibility are not expected to be useful in a clinical setting. The nalidixic acid disc is a marker of ciprofloxacin susceptibility as the nalidixic acid-susceptible strains were susceptible to ciprofloxacin while most of the resistant ones were resistant to ciprofloxacin. Overall, our results suggest that disc diffusion is a reliable, easy and inexpensive susceptibility testing method for C. jejuni and C. coli for erythromycin, ciprofloxacin and tetracycline. Until more erythromycin- and ciprofloxacin-resistant strains are tested to confirm the reliability of this test, the resistance to these drugs needs to be confirmed using the Etest or the agar dilution method.
authors.affiliation: Service de Microbiologie Médicale et Maladies Infectieuses, Hôpital Saint-Luc and Université de Montréal, Québec, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Gaudreau
authors.forename: H
authors.initials: H
authors.lastname: Gilbert
mesh_terms: D000667:Ampicillin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000890:Anti-Infective Agents / Q000494:pharmacology; D017000:Campylobacter coli / Q000187:drug effects* / Q000502:physiology; D016123:Campylobacter jejuni / Q000187:drug effects* / Q000502:physiology; D002939:Ciprofloxacin / Q000494:pharmacology; D015169:Colony Count, Microbial / Q000379:methods*; D004058:Diffusion; D004917:Erythromycin / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D013223:Statistics as Topic; D013752:Tetracycline / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D002939:Ciprofloxacin; D004917:Erythromycin; D000667:Ampicillin; D013752:Tetracycline