本文从一份糙米样品中分离纯化出5株细菌，分别命名为BR1、BR2、BR3、BR4和BR5，对其进行形态学观察、生理生化鉴定、16S rRNA及gyrB基因测序鉴定，并对其毒力基因及药物敏感性等生物学特征进行研究。结果表明，5株分离菌株生化特性符合蜡样芽孢杆菌（Bacillus cereus）的特性，结合16S rRNA及gyrB基因测序结果，菌株BR1和BR4鉴定为蜡样芽孢杆菌。毒力基因的PCR检测结果表明，菌株BR1和BR4携带肠毒素基因（hbl、nhe、entFM和bceT）和细胞毒素K基因（cytK），未检测到呕吐型毒力基因（cer和ces）。菌株BR1和BR4对青霉素、氨苄西林和头孢噻肟等药物耐药，对阿莫西林中度敏感，对诺氟沙星、环丙沙星和庆大霉素等药物敏感。本研究通过分离鉴定糙米源蜡样芽孢杆菌，发现分离菌株携带多种毒力基因，并且对青霉素类、头孢菌素类及磺胺类等药物耐药，表明糙米中的蜡样芽孢杆菌有引起食源性疾病的风险。

In this study, five strains of bacteria were isolated and purified from one sample of brown rice, which were named BR1, BR2, BR3, BR4 and BR5, respectively. Morphology, biochemical tests, and 16S rRNA combined with gyrB gene sequencing were performed to identify the bacteria. Virulence genes detection and drug sensitivity testing were also performed on the bacteria. The results showed that the biochemical characteristics of the five isolates were consistent with Bacillus cereus, and the strains BR1 and BR4 were identified as B. cereus by sequence analysis of 16S rRNA gene and gyrB gene. The detection results of virulence gene PCR showed that the strains BR1 and BR4 harbor virulence-coding genes hbl, nhe, entFM, bceT and cytK. Drug sensitivity testing showed that the strains BR1 and BR4 were resistant to multiple drugs such as penicillin, ampicillin, cefotaxime, etc., moderately sensitive to amoxicillin, sensitive to multiple drugs such as norfloxacin, ciprofloxacin, gentamicin, etc. This study indicated that a variety of virulence genes in B. cereus brown rice isolates were detected, and the strains were resistant to penicillins, cephalosporins and sulfonamides, which had a potential threat to food safety.

国家自然科学基金项目（31801658）；陕西省重点研发计划项目（2018YBXM-SF-17-8）；陕西省自然科学基础研究计划项目（2020JQ-269）