Long-term observation of antimicrobial susceptibility and molecular characterization of Campylobacter jejuni isolated in a Japanese general hospital in Tokyo from 2000 to 2017.

OBJECTIVES: Campylobacter jejuni is one of the most common pathogens causing gastroenteritis. Because there is currently insufficient epidemiological information on the antimicrobial susceptibility and molecular characterization of clinical isolates of C. jejuni in Japan, we carried out antimicrobial susceptibility testing, and MLST of clinical C. jejuni isolates in Tokyo between 2000 and 2017.

METHODS: Antimicrobial susceptibility to erythromycin and ciprofloxacin was tested in 430 clinical isolates of C. jejuni collected over 18 years in a Tokyo general hospital between 2000 and 2017 using the broth microdilution method. To observe the sequence type (ST) evolution, 82 isolates were chosen from three nonconsecutive years (16 isolates from 2000, 25 isolates from 2008, and 41 isolates from 2017) and analyzed by MLST as a molecular characterization test. The mutations in the quinolone resistance-determining region of the gyrA and gyrB genes were identified.

RESULTS: The rate of resistance to erythromycin was low, but that of ciprofloxacin resistance was 34.9% in 2000-2008 and 41.9% in 2009-2017. The most common clonal complex (CC) identified during the entire period was CC21. ST4526 with ciprofloxacin resistance was highly prevalent in 2017 (6/11; 54.5%).

CONCLUSION: Our results indicated that the rate of resistance to quinolone has gradually increased. Since ST4526 was not isolated in 2000 and 2008, it is likely that ST4526 has rapidly expanded recently in Japan.