Table_3_A Study on Prevalence and Characterization of Bacillus cereus in Ready-to-Eat Foods in China.DOCX

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.

蜡样芽孢杆菌（Bacillus cereus）广泛分布于各类食品中，可引发多种与食物中毒相关的病症。由于即食食品（RTE）在食用前通常无需经过热处理灭菌，蜡样芽孢杆菌污染可能引发严重的食品安全问题。本研究针对中国不同地区采集的即食食品样本中的蜡样芽孢杆菌流行情况展开调查，并对分离株的细菌污染水平、抗生素耐药性、毒力基因分布及遗传多态性进行了评估。本次检测的零售即食食品中，35%的样本呈蜡样芽孢杆菌阳性；分离得到的菌株中，分别有39%和83%携带编码肠毒素的hblACD与nheABC基因簇。所有蜡样芽孢杆菌菌株均检出entFM基因；68%的分离株携带cytK基因，但仅7%的菌株携带编码呕吐毒素的cesB基因。药敏试验结果显示，多数分离株不仅对大多数β-内酰胺类抗生素耐药，同时对利福霉素类亦存在耐药性。多位点序列分型（MLST）结果表明，368株分离株隶属于192种不同的序列型（STs），其中包含93种新的序列型，最常见的序列型为ST26。综上，本研究明确了中国即食食品中分离的蜡样芽孢杆菌的流行情况、污染水平及生物学特性，证实了即食食品中蜡样芽孢杆菌的潜在危害。