Prevalence and molecular characterization of Escherichia coli isolates during radish sprout production in the Republic of Korea

This study was conducted to investigate the prevalence of coliforms and Escherichia coli across radish sprout production facilities in the Republic of Korea and to characterize isolated E. coli. A total of 324 samples were collected from three different radish sprout production units in spring and summer. Overall, the levels of coliforms were significantly higher (> 3.75 log CFU/g) in radish sprouts during summer season than in spring. E. coli was detected in the pre-harvest (50%) and post-harvest (39%) sprouts and water samples (33%) from farms B and C. Of the 48 E. coli isolates, five E. coli isolates were positive for the eaeA gene, indicative of EPEC O110, two isolates were eaeA-positive (EPEC ONT) and one isolate was ipaH-positive (ETEC O71). These three E. coli strains were identified as novel sequence types by the multilocus sequence-typing assay based on the combination of allelic profiles. In addition, the EPEC O110 isolates obtained from the stream water stored in container of farm C were toxic to Caenorhabditis elegans. It is necessary to implement safety measures during the production of radish sprouts to prevent E. coli outbreaks.