Hwang Ji-Yeon, Park Jong-Hyun
Department of Food Science and Biotechnology, Gachon University, Sungnam 461-701, Republic of Korea.
Department of Food Science and Biotechnology, Gachon University, Sungnam 461-701, Republic of Korea.
J Dairy Sci. 2015 Mar;98(3):1652-60. doi: 10.3168/jds.2014-9042. Epub 2015 Jan 15.
Bacillus cereus is a ubiquitous environmental microbe implicated as a main cause of food poisoning with various symptoms, depending on the strain type and the isolation source. In this study, the potential virulence factors and biochemical properties of B. cereus isolated from infant formulas and ready-to-eat (RTE) foods were analyzed and compared. A total of 347 B. cereus strains were isolated and identified from 687 infant food formulas and RTE food samples. All the isolates had one or more enterotoxin genes, and one-half of the strains had all 3 enterotoxin genes (hbl, nhe, and cytK) that are involved in food poisoning in humans. Here, all the 3 genes were detected in 50% of the B. cereus isolates from RTE foods and only 14% of the isolates were identified from infant formulas. The latter harbored low cytK and bceT, and very low hbl genes. Most B. cereus isolates possessed the hemolysis gene, but not the ces gene. The infant formula isolates showed stronger hemolysis activity than the other isolates. In addition, 26% of the total isolates showed low lecithinase activities and 10% showed high lecithinase activities. A greater number of isolates from the infant formula showed high lecithinase activity than those from the RTE foods. Approximately 83% of the isolates were positive and 17% were negative for starch hydrolysis. Over 90% of the RTE food isolates and only 35% of the infant formula isolates were positive for starch hydrolysis. However, all the strains possessed nhe, but their harboring patterns of hbl and cytK were significantly different. Most starch-hydrolyzing strains possessed hbl, but only 23% nonstarch-hydrolyzing isolates possessed this gene. Moreover, very low nonstarch hydrolyzing strains harbored cytK. Most nonstarch-hydrolyzing isolates showed high lecithinase and strong hemolysis activities, and very low hbl and cytK harboring. In summary, most infant formula isolates showed stronger hemolysis and higher lecithinase activities with lower frequency of harboring hbl and cytK and lower starch hydrolysis compared with RTE food isolates.
蜡样芽孢杆菌是一种普遍存在的环境微生物，是食物中毒的主要原因之一，其症状因菌株类型和分离来源而异。在本研究中，对从婴儿配方奶粉和即食（RTE）食品中分离出的蜡样芽孢杆菌的潜在毒力因子和生化特性进行了分析和比较。从687份婴儿食品配方奶粉和RTE食品样本中总共分离并鉴定出347株蜡样芽孢杆菌菌株。所有分离株都有一个或多个肠毒素基因，其中一半的菌株拥有与人类食物中毒相关的全部3种肠毒素基因（hbl、nhe和cytK）。在此，50%的RTE食品蜡样芽孢杆菌分离株中检测到了所有3种基因，而婴儿配方奶粉中仅14%的分离株检测到这些基因。后者的cytK和bceT基因含量较低，hbl基因含量极低。大多数蜡样芽孢杆菌分离株拥有溶血基因，但不拥有ces基因。婴儿配方奶粉分离株的溶血活性比其他分离株更强。此外，26%的分离株卵磷脂酶活性较低，10%的分离株卵磷脂酶活性较高。婴儿配方奶粉中显示出高卵磷脂酶活性的分离株数量比RTE食品中的更多。约83%的分离株淀粉水解呈阳性，17%呈阴性。超过90%的RTE食品分离株淀粉水解呈阳性，而婴儿配方奶粉分离株中只有35%呈阳性。然而，所有菌株都拥有nhe，但它们的hbl和cytK携带模式存在显著差异。大多数淀粉水解菌株拥有hbl，但只有23%的非淀粉水解分离株拥有该基因。此外，非淀粉水解菌株中cytK的携带率极低。大多数非淀粉水解分离株显示出高卵磷脂酶和强溶血活性，hbl和cytK携带率极低。总之，与RTE食品分离株相比，大多数婴儿配方奶粉分离株显示出更强的溶血和更高的卵磷脂酶活性，hbl和cytK携带频率更低，淀粉水解率更低。
