Antimicrobial resistance, molecular, and phenotypic diversity of Escherichia coli isolates from fresh vegetable products in Korea

Escherichia coli is generally considered as an indicator of antimicrobial resistance due to its genetic flexibility and adaptability. In the present study, antimicrobial resistance patterns, biofilm formation ability, and genotypes were assessed in E. coli isolates from fresh vegetable products in Korea. Among 120 isolates, 22 isolates (18.3 %) were resistant to one or more antimicrobials and 11 isolates were concurrently multidrug resistant against up to six antimicrobial agents. The highest resistance rate was detected on ampicillin (14.2 %), followed by piperacillin (11.7 %) and cefalotin (10.0 %). Rep-Polymerase chain reaction (PCR) revealed that five out of the 26 isolates were assigned to one cluster with a similarity >95 %, and strains carrying the same antimicrobial resistance profile had discrete rep-PCR patterns. A biofilm formation assay demonstrated that significantly larger amounts of biofilm were formed by an isolate, which showed no antimicrobial resistance. However, 60 % of the five intermediated biofilm-forming E. coli exhibited multidrug resistance against three or four antimicrobial agents. These results suggest that fresh vegetable products contaminated with E. coli are sources of antimicrobial resistance and other diverse virulence determinants. Therefore, the information provided in this study can be useful for improving food safety and public health.