Abstract

Bacillus cereus is widely distributed in different food products and can cause a variety of symptoms associated with food poisoning. Since ready-to-eat (RTE) foods are not commonly sterilized by heat treatment before consumption, B. cereus contamination may cause severe food safety problems. In this study, we investigated the prevalence of B. cereus in RTE food samples from different regions of China and evaluated the levels of bacterial contamination, antibiotic resistance, virulence gene distribution, and genetic polymorphisms of these isolates. Of the tested retail RTE foods, 35% were positive for B. cereus, with 39 and 83% of the isolated strains harboring the enterotoxin-encoding hblACD and nheABC gene clusters, respectively. The entFM gene was detected in all B. cereus strains. The cytK gene was present in 68% of isolates, but only 7% harbored the emetic toxin-encoding gene cesB. Antimicrobial susceptibility testing revealed that the majority of the isolates were resistant not only to most β-lactam antibiotics, but also to rifamycin. Multilocus sequence typing (MLST) revealed that the 368 isolates belonged to 192 different sequence types (STs) including 93 new STs, the most prevalent of which was ST26. Collectively, our study indicates the prevalence, bacterial contamination levels, and biological characteristics of B. cereus isolated from RTE foods in China and demonstrates the potential hazards of B. cereus in RTE foods.

Highlights

  • Ready-to-eat (RTE) foods, such as cooked meats and poultry, cold vegetable dishes in sauce, cold noodles, and fried rice, are very popular as they are intended for direct consumption

  • This study investigated the potential pathogenicity, contamination levels, molecular characteristics, and antibiotic resistance profiles of B. cereus isolated from RTE foods in China, providing important information about the prevalence of B. cereus in RTE foods

  • Since B. cereus is widespread in nature, in soil, vegetables are contaminated by this bacterium; previously, we showed consumption of cold vegetable dishes in sauce made from that B. cereus was present in up to 50% of vegetables (Yu vegetables contaminated with B. cereus could increase the et al, 2019)

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Summary

Introduction

Ready-to-eat (RTE) foods, such as cooked meats and poultry, cold vegetable dishes in sauce, cold noodles, and fried rice, are very popular as they are intended for direct consumption. They are very convenient for consumers, RTE foods have been shown to be frequently contaminated with pathogenic bacteria such as Bacillus cereus, Listeria monocytogenes, and Staphylococcus aureus (Batchoun et al, 2011; Hwang and Park, 2015; Wu et al, 2016; Yang et al, 2016). Numerous food poisoning incidents caused by B. cereus have been reported recently in Spain (Doménech-Sánchez et al, 2011), Belgium (Delbrassinne et al, 2015), Argentina (Lopez et al, 2015), Australia (Sloan-Gardner et al, 2014), England (Nicholls et al, 2016), Austria (Schmid et al, 2016), and France (Glasset et al, 2016)

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