Antibiotic resistance in Campylobacter jejuni isolated from humans in the Hunter Region, New South Wales.

Campylobacter is a common cause of bacterial gastroenteritis in Australia. Antibiotic resistance among Campylobacter is an emerging problem in Europe and the United States of America. Monitoring may detect emerging resistance. Since there is no epidemiologically validated subtyping system for Campylobacter, antimicrobial resistance patterns may prove useful as an epidemiological marker. Campylobacter isolates from residents of the Hunter region were differentiated by PCR into two categories: C. jejuni and non-C. jejuni. Minimal inhibitory concentrations (MIC) were determined for 10 antibiotics using the National Committee for Clinical Laboratory Standards (NCCLS) agar dilution methodology. Risk factor information including travel history were obtained as part of a case-control study by conducting telephone interviews with infected individuals. Sixty-four per cent, 3.4 per cent, 3.4 per cent and 11.2 per cent of C. jejuni isolates were resistant to ampicillin (at MIC > 8 mg/L), erythromycin (> 8 mg/L), nalidixic acid (> 32 mg/L) and tetracycline (> 8 mg/L), respectively. A diverse pattern of antibiotic resistance ('resistotypes') was detected with some change occurring over time. Several possible clusters of Campylobacter infections were identified based on resistotype. Of seven infections acquired during overseas travel, 57 per cent (4/7) were resistant to more than one antibiotic class compared to 10 per cent (14/144) of locally-acquired isolates (p=0.004, Fisher exact). The potential usefulness of resistotyping as an epidemiological marker is worthy of further exploration.