Assessment and molecular characterization of Bacillus cereus isolated from edible fungi in China
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RESEARCH ARTICLE
Open Access
Assessment and molecular characterization of Bacillus cereus isolated from edible fungi in China Chengcheng Liu1,2†, Pengfei Yu1,2†, Shubo Yu1, Juan Wang3, Hui Guo1,2, Ying Zhang1,2, Junhui Zhang1,2, Xiyu Liao1,2, Chun Li2, Shi Wu1, Qihui Gu1, Haiyan Zeng1, Youxiong Zhang1, Xianhu Wei1, Jumei Zhang1, Qingping Wu1* and Yu Ding1,2*
Abstract Background: Bacillus cereus is a foodborne pathogen commonly found in nature and food and can cause food spoilage and health issues. Although the prevalence of B. cereus in foods has been reported worldwide, the extent of contamination in edible fungi, which has become increasingly popular as traditional or functional food, is largely unknown. Here we investigated the prevalence, toxin genes’ distribution, antibiotic resistance, and genetic diversity of B. cereus isolated from edible fungi in China. Results: Six hundred and ninety-nine edible fungi samples were collected across China, with 198 (28.3%) samples found to be contaminated by B. cereus, with an average contamination level of 55.4 most probable number (MPN)/g. Two hundred and forty-seven B. cereus strains were isolated from the contaminated samples. Seven enterotoxin genes and one cereulide synthetase gene were detected. The detection frequencies of all enterotoxin genes were ≥ 80%, whereas the positive rate of the cesB gene in B. cereus was 3%. Most isolates were resistant to penicillins, β-lactam/β-lactamase inhibitor combinations, cephems, and ansamycins, but were susceptible to penems, aminoglycosides, macrolides, ketolide, glycopeptides, quinolones, phenylpropanol, tetracyclines, lincosamides, streptogramins, and nitrofurans. Meanwhile, 99.6% of all isolates displayed multiple antimicrobial resistance to three or more classes of antimicrobials. Using genetic diversity analysis, all isolates were defined in 171 sequence types (STs), of which 83 isolates were assigned to 78 new STs. Conclusions: This study provides large-scale insight into the prevalence and potential risk of B. cereus in edible fungi in China. Approximately one-third of the samples were contaminated with B. cereus, and almost all isolates showed multiple antimicrobial resistance. Detection frequencies of all seven enterotoxin genes were equal to or more than 80%. These new findings may indicate a need for proper pre-/post-processing of edible fungi to eliminate B. cereus, thereby preventing the potential risk to public health. Keywords: Bacillus cereus, Edible fungi, Prevalence, Antibiotic resistance, Genetic diversity
* Correspondence: [email protected]; [email protected] † Chengcheng Liu and Pengfei Yu contributed equally to this work. 1 Guangdong Institute of Microbiology, Guangdong Academy of Science, State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbial Safety and Health, Guangdong Open Laboratory of Applied Microbiology, Xianlie Zhong Road 100#, 58th Building, Guangzhou 510070, China Full list of author information is available at the end of the article © The
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