Purpose: The objective of this study was to determine serotypes, antimicrobial resistance, and genetic correlation for E. coli isolated from raw kimchi ingredients and fermented kimchi.
Methods: One hundred raw kimchi ingredients [nappa cabbage (n=30), white radish (n=30), leek (n=20), and ginger (n=20)] and kimchi samples [nappa cabbage kimchi (n=20) and diced white radish kimchi (n=20)] were analyzed. Coliform and E. coli cell counts were enumerated on 3M™ Petrifilm™ at 37°C for 24 h. Typical E. coli colonies on the Petrifilm were identified by 16S rRNA analysis and multiplex PCR method. The identified E. coli was serotyped by immune assay. The antimicrobial susceptibilities of E. coli isolates were determined by a disc diffusion assay. To determine genetic correlation among the isolates, pulsed-field gel electrophoresis (PFGE) analysis were performed.
Results: Escherichia coli were isolated from nappa cabbage (1 of 30; 3.3%), nappa cabbage kimchi (3 of 20; 15%) and diced white radish kimchi (3 of 20; 15%). All isolates were then determined as E. coli by 16S rRNA analysis. The pathotypes were enterohemorrhagic E. coli (stx 2 positive) for E. coli from nappa cabbage and enteropathogenic E. coli (eaeA positive and bfpA positive or negative) for E. coli from all kimchi samples. Serotypes for the E. coli isolates were O6 for nappa cabbage and O20 for one colony from diced white radish kimchi. Isolated E. coli showed various antimicrobial susceptibility, and PFGE result showed close genetic correlation among the isolates.
Significance: This result suggests that characteristics of E. coli isolated from raw kimchi ingredients and fermented kimchi could be useful in understanding the cause of foodborne illness by kimchi consumption.