Laboratório de Fisiologia Bacteriana, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, FIOCRUZ, RJ, Brazil.
Int J Food Microbiol. 2011 May 14;147(1):12-6. doi: 10.1016/j.ijfoodmicro.2011.02.029. Epub 2011 Mar 1.
Bacillus cereus is an ever-present problem. It is widely distributed in several environments such as soil and plants and is commonly isolated from food and additives. In this study we analyzed 97 foodborne B. cereus sensu stricto strains isolated in Brazil in the 1980's, 1990's and 2000's in order to investigate the genetic diversity (assessed by Rep-PCR), antimicrobial resistance and toxigenic profiles (presence of hblA, hblC and hblD; nheA, nheB and nheC as well as cytK, ces and entFM genes) of such strains. The majority of the strains (79, 81.4%) were β-hemolytic. The NHE complex was found in 82 strains (84.5%) and HBL complex was found in 61 (62.9%) strains. All strains were negative to ces. The cytK-2 gene was found in 44 (45.4%) strains. The predominant toxigenic pattern was type I (32, 33%) which included strains positive for all toxin genes but ces. Computer assisted cluster analysis of Rep-PCR profiles showed a high genetic diversity. Seven major clusters comprising two or more strains were found and cluster 1 was predominant (ten strains, nine of them showing 100% similarity). This cluster included strains isolated in the 1980's and the 1990's. Cluster analysis of Rep-PCR profiles based on decade of isolation, source, hemolytic pattern, toxigenic and antibiotic resistance patterns revealed a similar clustering pattern as found in the analysis including all strains. The inability to observe a predominant band pattern when Rep-PCR cluster analysis was based on decade of isolation suggests that this diversity has been maintained over time. All strains were susceptible to gentamicin. We detected resistance to tetracycline (11 strains showing intermediate resistance and nine completely resistant strains), clindamycin (ten intermediate strains) and vancomycin (one strain). Clindamycin resistance showed statistical association with strains isolated in 2000's. The predominant resistance pattern was type A (72, 72.2%) which included strains susceptible to all drugs tested. Our results suggest that the majority of the strains present in several types of food in Brazil pose a potential risk to cause food poisoning due to the high prevalence of toxin genes found in these strains. However, additional studies involving cytotoxicity tests and affiliation of these strains to phylogenetic groups based on molecular data would be useful to better evaluate this potential and could provide a more accurate indication of the risk.
蜡样芽胞杆菌是一个普遍存在的问题。它广泛分布于土壤和植物等多种环境中，通常从食品和添加剂中分离出来。在这项研究中，我们分析了 1980 年代、1990 年代和 2000 年代在巴西分离的 97 株食源性蜡样芽胞杆菌，以研究其遗传多样性（通过 Rep-PCR 评估）、抗药性和产毒谱（hblA、hblC 和 hblD；nheA、nheB 和 nheC 以及 cytK、ces 和 entFM 基因的存在）。大多数菌株（79，81.4%）为β-溶血。82 株菌中发现了 NHE 复合物（84.5%），61 株菌中发现了 HBL 复合物（62.9%）。所有菌株均为 ces 阴性。44 株菌（45.4%）中发现 cytK-2 基因。主要产毒模式为 I 型（32，33%），包括所有毒素基因均阳性但 ces 阴性的菌株。Rep-PCR 图谱的计算机辅助聚类分析显示出很高的遗传多样性。发现了七个主要的包含两个或更多菌株的聚类，其中聚类 1 占主导地位（10 株，其中 9 株具有 100%的相似性）。该聚类包括 1980 年代和 1990 年代分离的菌株。基于分离年代、来源、溶血模式、产毒和抗生素耐药模式的 Rep-PCR 图谱聚类分析显示出与包括所有菌株的分析中相似的聚类模式。基于分离年代的 Rep-PCR 聚类分析未能观察到主要带型模式表明，这种多样性随着时间的推移得以维持。所有菌株均对庆大霉素敏感。我们检测到对四环素（11 株表现为中介耐药，9 株完全耐药）、克林霉素（10 株中介耐药）和万古霉素（1 株）的耐药性。克林霉素耐药与 2000 年代分离的菌株呈统计学关联。主要耐药模式为 A 型（72，72.2%），包括对所有测试药物敏感的菌株。我们的结果表明，巴西多种类型食品中存在的大多数菌株由于这些菌株中发现的毒素基因高流行率，可能构成食物中毒的潜在风险。然而，涉及细胞毒性试验和基于分子数据将这些菌株与系统发育群相关联的额外研究将有助于更好地评估这种潜在风险，并提供更准确的风险指示。
