摘要：
Bacillus cereus is a pathogen related with diarrhoeal or emetic food poisoning cases, of which the latter caused by the cereulide-producing isolates are more severe with several reported lethal cases. It is therefore necessary to develop an effective strategy to prevent the propagation of B. cereus in the food supply. In this study, three autolysins from the cereulide-producing B. cereus group isolates, LysIS075, LysF8819.1 and Ly5CER057, were identified and characterized. The results showed that the three autolysins were highly lytic and bactericidal to the tested cereulide-producing B. cereus group strains and cross-lytic against other tested B. cereus group strains, and they could inhibit the spore germination and propagation of their tested derived emetic strains. Physical and chemical characterization showed that all the three autolysins were alkalophilic with the optimal activity at pH 9.0 or 9.5 with one exception of LysF8819.1 also having significant lytic activity at pH 5.0, and they all had relative strong lyric activity at 37-50 degrees C during the 30 minute assay. However, LysCER057 showed relative susceptibility to thermo-condition. Remarkably, the separate or cock-tail addition of the three autolysins in food matrices (milk and rice porridge) showed effective bactericidal activity within the tested 2 h. All the results revealed that the three autolysins might be potential candidates to control emetic B. cereus strains in different applications. (C) 2016 Published by Elsevier B.V.
作者机构：
[周帼萍; 高雯] School of Biology and Pharmaceutical Engineering, Wuhan Polytechnic University, Wuhan, 430023, China;[胡晓敏] Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, China
摘要：
Bacillus cereus strains containing voitoxin cereulide are pathogenic bacteria. The cereulide is produced by B. cereus strains containing plasmid pCER270. To establish a specific loop-mediated isothermal amplification (LAMP) method detecting pathogenic B. cereus, LAMP primer sets were designed based on 16SrDNA and pCER270 plasmid cesA sequence. The LAMP reaction was carried out under optimal conditions with 2 mM of Mg2+ at 65C for 1 h. Specificity of LAMP primers were validated by assaying 19 B. cereus strains with and without pCER270 plasmid and 42 non-B. cereus species. Detection limits of the LAMP assay were 1 cfu/mL of B. cereus without pCER270 plasmid and 11 cfu/mL of pathogenic B. cereus with pCER270 plasmid. Furthermore, liquid milk samples were detected by the LAMP method. The results showed that LAMP method is a reliable method used for rapid detection of B. cereus and its pathogenic strains of milk and other food stuff.
Loop-mediated isothermal amplification (LAMP) is a novel nucleic acid amplification method. In this study LAMP method was specific and sensitive for detection of B. cereus which grown in liquid medium or on solid medium, or from liquid milk samples as well. In addition, the pathogenic strains expressed voitoxin cereulide could be readily identified after amplification using specific LAMP primer sets. The whole procedure is simple and rapid, the reaction carried out in tens of minutes at a constant temperature. LAMP could be routinely used for B. cereus especially pathogenic strains in food.
摘要：
The occurrences of Bacillus cereus group strains in 40 ice cream samples were investigated. Among 109 isolated B. cereus group strains confirmed by 16S rDNA sequence analysis only 50 were identified as B. cereus and one as B. thuringiensis by using FDA (U.S. Food and Drug Administration) standard, indicating the two identification standards were highly inconsistent. Furthermore, the psychrotolerant growth properties and the occurrence of specific psychrotolerant genes of the isolates were also studied. Both psychrotolerant 16S rDNA fragments and enterotoxic genes could be detected among mesophilic and psychrotolerant strains. No relationship among psychrotolerance, presence of psychrotolerant 16S rDNA fragments and enterotoxic genes were found and the specific cspA fragment was only detected in a small fraction (9.5%) of the psychrotolerant isolates. One psychrotolerant isolate Bw2-1 was identified as B. weihenstephanensis, but no clear distinguishing characteristics between B. weihenstephanensis and psychrotolerant B. cereus were found. These results might be of importance for gaining further understanding of the growth properties of B. weihenstephanensis and psychrotolerant B. cereus as well as their contribution to food poisoning.
期刊：
International Journal of Food Microbiology,2008年121(2):195-200 ISSN：0168-1605
通讯作者：
Yuan, Zhiming
作者机构：
[Liu, Haizhou; Yuan, Zhiming; Zhou, Guoping; Yuan, Yongming] Chinese Acad Sci, State Key Lab Virol, Wuhan Inst Virol, Wuhan 430071, Peoples R China.;[Zhou, Guoping; He, Jing] Wuhan Polytech Univ, Dept Bioengn & Pharmaceut Engn, Wuhan 430023, Peoples R China.;[Liu, Haizhou; Zhou, Guoping; Yuan, Yongming] Chinese Acad Sci, Grad Sch, Beijing 100039, Peoples R China.
通讯机构：
[Yuan, Zhiming] C;Chinese Acad Sci, State Key Lab Virol, Wuhan Inst Virol, Wuhan 430071, Peoples R China.
关键词：
B. mycoides;B. thuringiensis;Bacillus cereus;Occurrence;Pasteurized full fat milk
摘要：
In 2006, a total of 54 samples of pasteurized full fat milk packaged in cartons were collected in spring and in autumn from chain supermarkets in Wuhan, China. The samples were examined and enumerated by MPN methods strictly according to guidelines laid out in US FDA/CFSAN BAM Chapter 14. Among 102 isolated B. cereus-like bacteria, 92 isolates were identified to be B. cereus, 9 B. thuringiensis and 1 B. mycoides. It was found that the occurrences of B. cereus were 71.4% and 33.3% in spring and in autumn samples respectively and the average count among the positive samples was 11.7 MPN/ml. The PCR detection results revealed that the enterotoxin genes hblA, hblC, hblD, nheA, nheB and nheC occurred in B. cereus isolates with frequencies of 37.0%, 66.3%, 71.7%, 71.7%, 62.0% and 71.7% respectively. Nine B. thuringiensis isolates were also identified from six pasteurized milk samples, and most of them harbored six enterotoxic genes and the insecticidal toxin cry1A gene. The single B. mycoides isolate harbored nheA and nheC genes. The data provides information for further evaluating the effect of B. cereus-like bacteria on food safety of Chinese milk products.
摘要：
In 2006, 54 pasteurized full fat milk samples, 40 ice-cream samples, and two green-tea beverage samples were analyzed and a total of 19 Bacillus thuringiensis-like strains were isolated, nine from seven pasteurized milks, one from an ice-cream with peach pulp and juice, and nine from two green-tea beverages. These strains were classified as B. thuringiensis, contained the cry1A gene and produced crystal inclusions during sporulation. All strains were characterized by a serotyping test, SDS-PAGE, random amplified polymorphic DNA, and enterotoxic gene PCR analysis. Most isolates produced bipyramidal crystals and belonged to serotypes H-3a3b, H-5a5b, or H-7. Furthermore. two strains from pasteurized full fat milks and three strains from green-tea beverages were indistinguishable from the B. thuringiensis subsp. kurstaki strains isolated from commercial biopesticides (Kaiyan (R), Qiangdi (R), Lvpuan (R) and Sutai (R)), suggesting the residual occurrences of B. thuringiensis from biopesticides in food and beverages. (C) 2008 Elsevier B.V. All rights reserved.
