Genetic analysis of Campylobacter jejuni isolates from diarrheal patients in South Korea (Jan. 2012-Feb. 2017)

Jung Su-Mi, Hong Sahyun, Kang Byung Hak, Kim Jae Ok
Division of Bacterial Diseases, Center for Laboratory Control of Infectious Diseases, KCDC

Background: Campylobacter jejuni is a major bacterial cause of human gastroenteritis worldwide, being associated with the ingestion of contaminated chicken. The aim of this study is to determine the molecular epidemiology of C. jejuni strains collected from diarrheal patients between January 2012 and February 2017.
Methodology: To identify the genetic variations in C. jejuni, multilocus sequence typing (MLST) was performed on 194 C. jejuni strains isolated from the cases of sporadic acute gastroenteritis (n = 150), food-poisoned diarrhea outbreak (n=26) and overseas travel-associated diarrhea (n = 18) in South Korea. The phylogenetic tree was constructed using the neighbor-joining algorithm with the software MEGA 6.
Results: MLST analyses of the 194 clinical isolates generated 58 different sequence types (STs) and 19 clonal complexes (CCs). MLST gene fragments varied in length from 402 to 507 bps, with average p distances of 0.008 (uncA gene fragment) to 0.025 (pgm gene fragment). Clonal complex 21 (45.9%) including ST-19, ST-21, ST-50, ST-760, ST-1811 and ST-4253 was dominant in this study. In CC 21, ST-21 was the most prevalent ST of C. jejuni in South Korea. A neighbor-joining tree was classified into three clusters, wherein 63.4% of the isolates was found in cluster 3.
Conclusions: In this study, domestic isolates and overseas travel-associated isolates can be distinguished by MLST analysis. Our results provide information on MLST type distribution and genetic relatedness of C. jejuni strains in South Korea.

Keywords: Gastroenteritis, Campylobacter jejuni, Genotic variation, Multilocus sequence typing, Phylogeny