Abstract
Bacillus cereus is a food-borne opportunistic pathogen that can induce diarrheal and emetic symptoms. It is widely distributed in different environments and can be found in various foods, including fresh vegetables. As their popularity grows worldwide, the risk of bacterial contamination in fresh vegetables should be fully evaluated, particularly in vegetables that are consumed raw or processed minimally, which are not commonly sterilized by enough heat treatment. Thereby, it is necessary to perform potential risk evaluation of B. cereus in vegetables. In this study, 294 B. cereus strains were isolated from vegetables in different cities in China to analyze incidence, genetic polymorphism, presence of virulence genes, and antimicrobial resistance. B. cereus was detected in 50% of all the samples, and 21/211 (9.95%) of all the samples had contamination levels of more than 1,100 MPN/g. Virulence gene detection revealed that 95 and 82% of the isolates harbored nheABC and hblACD gene clusters, respectively. Additionally, 87% of the isolates harbored cytK gene, and 3% of the isolates possessed cesB. Most strains were resistant to rifampicin and β-lactam antimicrobials but were sensitive to imipenem, gentamicin, ciprofloxacin, kanamycin, telithromycin, ciprofloxacin, and chloramphenicol. In addition, more than 95.6% of the isolates displayed resistance to three kinds of antibiotics. Based on multilocus sequence typing, all strains were classified into 210 different sequence types (STs), of which 145 isolates were assigned to 137 new STs. The most prevalent ST was ST770, but it included only eight isolates. Taken together, our research provides the first reference for the incidence and characteristics of B. cereus in vegetables collected throughout China, indicating a potential hazard of B. cereus when consuming vegetables without proper handling.
Highlights
Bacillus cereus is a Gram-positive, spore-forming opportunistic pathogen that is widespread in different environments and known to cause foodborne outbreaks in humans (Bottone, 2010; Osimani et al, 2018)
QW, JW, and YD complemented the writing. Vegetables such as L. esculentum Mill., C. sativus L., var. ramosa Hort., and so on are usually consumed directly or with minimal processing, so potential hazards associated with B. cereuscontaminated vegetables should not be ignored
The results in this study revealed a high incidence of B. cereus in vegetable samples collected from across China, for the first time as we know
Summary
Bacillus cereus is a Gram-positive, spore-forming opportunistic pathogen that is widespread in different environments and known to cause foodborne outbreaks in humans (Bottone, 2010; Osimani et al, 2018). B. cereus in food products at concentrations exceeding 104 spores or vegetative cells per gram can cause food poisoning (Ehling-Schulz et al, 2006; Fricker et al, 2007; Meldrum et al, 2009). Prevalence of potential emetic and diarrheal B. cereus in different foods has been reported in Finland (Shaheen et al, 2010), Belgium (Rajkovic et al, 2006), Thailand (Chitov et al, 2008), the United Kingdom (Altayar and Sutherland, 2006; Meldrum et al, 2009), the United States (Ankolekar et al, 2009), South Korea (Park et al, 2009), and Africa (Ouoba et al, 2008). From 1994 to 2005, 1,082 food poisoning cases caused by foodborne pathogens had been reported in China. B. cereus caused 145 (13.4%) of these cases, leading to six deaths (Wang et al, 2007)
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