Phenotypic and virulence traits of Escherichia coli and Salmonella strains isolated from vegetables and fruits from India.

AIMS: The present study was designed to assess the phenotypic traits and virulence determinants of vegetable-/fruit-origin Escherichia coli and Salmonella strains.

METHODS AND RESULTS: A total of 520 fresh vegetables/fruits samples were analysed for the presence of E. coli, including Shiga toxin-producing E. coli (STEC), and Salmonella. The vegetable-/fruit-origin E. coli and Salmonella strains were further assessed for antimicrobial resistance, biofilm formation, extracellular matrix production and in vitro invasion/intracellular survivability assays. A total of 73 E. coli, including four STEC, and 26 Salmonella strains were recovered from vegetables/fruits in the present study. Most of the E. coli and Salmonella isolates were able to form biofilm with higher production of cellulose/curli-fimbriae. Furthermore, more resistance was observed in E. coli isolates (61·6%) than in Salmonella isolates (38·5%) against tested antimicrobials. Additionally, invasion/intracellular survival results showed that majority of the E. coli and Salmonella isolates were able to efficiently invade/replicate intracellularly in the human epithelial cells.

CONCLUSIONS: Our results demonstrate that vegetable-/fruit-origin E. coli and Salmonella significantly exhibited distinct phenotypic/virulence traits which could be linked to their plant-associated lifestyle with food safety issues.

SIGNIFICANCE AND IMPACT OF THE STUDY: The present study provides valuable baseline information that E. coli and Salmonella may use plants as an alternative host with significant clinical importance.