Detection of Escherichia coli O157:H7 and Salmonella enterica serotype Typhimurium based on cell elongation induced by beta-lactam antibiotics.

ABSTRACT

Pathogenic bacteria such as Shiga toxigenic Escherichia coli and Salmonella can cause severe food-borne diseases. Rapid and sensitive detection of these foodborne pathogens is essential to ensure food safety. In this study, a novel method based on cell elongation induced by beta-lactam antibiotics for direct microscopic counting of Gram-negative bacteria was established. Combined with the sample preparation steps of membrane filtration and magnetic separation, the detection of E. coli O157H7 and Salmonella enterica serotype Typhimurium was achieved by direct optical microscopic counting of the number of elongated bacteria. The limit of detection of E. coli O157H7 and S. typhimurium could reach 20 CFU mL-1. The recovery tests for E. coli O157H7 and S. typhimurium in water and milk samples showed acceptable recovery values between 93.6% and 106.2%. This method is sensitive, cost effective, and rapid (<2 h) and shows great potential for the detection of Gram-negative pathogens in various environmental and food samples.