Antimicrobial Resistance Patterns and Corresponding Multilocus Sequence Types of the Campylobacter jejuni Isolates from Human Diarrheal Samples

A total of 121 Campylobacter isolates from 4,788 humans with gastroenteritis were identified and characterized by biochemical detection methods, polymerase chain reaction, and multilocus sequence typing (MLST). These samples were obtained during a 3-year period, from January 2007 to December 2009, using the National Notifiable Diseases Surveillance System at the Research Institute of Public Health and Environment in Seoul Metropolitan, Korea. Antimicrobial susceptibilities of the bacterium were also determined with the agar dilution method. All 121 isolates were identified as Campylobacter jejuni, with all (100%) of them having two virulence genes (ceuE and cadF) and a toxin gene (cdtB). Twenty-three different sequence types (STs), including 9 new STs, were determined by MLST. The most prevalent ST and clonal complex (CC) observed in this study were ST-45 (28.9%) and ST-45 CC (53.7%), respectively. Percentages of antimicrobial-resistant isolates were 1.9% for ampicillin, 0.8% for chloramphenicol, 24% for ciprofloxacin, 46.3% for enrofloxacin, 0.8% for erythromycin, 6.6% for gentamicin, and 46.3% for tetracycline. This study demonstrated that the majority of the Campylobacter isolates obtained from human samples in Korea were C. jejuni with ST-45 CC, which has been detected mainly in broilers worldwide, and all strains with new STs were uniformly resistant to enrofloxacin and tetracycline. This study indicates that broilers may be a breeding ground for bacteria as well as an important potential source of human campylobacteriosis.