蜡样芽胞杆菌在不同标本中的毒力基因分布特征

Distribution of virulence genes of Bacillus cereus in several specimens

目的 研究蜡样芽胞杆菌毒力基因在不同标本中的分布特征。方法 分离自环境监测标本(米粉、奶粉、土壤)和疾病相关标本(米饭、凉皮、眼内炎和肿瘤患者)的蜡样杆菌333株,PCR扩增蜡样杆菌11个毒力基因,包括溶血性BL基因(hblC、hblD、hblA、hblB)、非溶血性基因(nheA、nheB、nheC)、肠毒素FM基因和T基因(entFM、bceT)、细胞毒素K基因(cytK)和呕吐毒素相关基因(ces),统计不同标本菌株中毒力基因的携带数目和各毒力基因的携带率,方差分析和卡方检验比较毒力基因在不同标本中,尤其是在疾病相关标本与环境监测标本中的携带差异。结果 研究菌株携带毒力基因平均数目为5.97个,88.29%的菌株携带至少3个毒力基因,12.31%的菌株携带除ces外的所有基因。标本携带毒力基因数目从高到低依次为患者(8.75)、凉皮(8.20)、米饭(7.13)、土壤(6.22)、米粉(5.78)和奶粉(5.71)。患者、凉皮分别与奶粉的基因数目两两比较有统计学差异显著性。菌株各毒力基因的携带率从高到低依次为非溶血性基因(89.19%)、entFM基因(79.88%)、bceT基因(49.85%)、溶血性BL基因(48.35%)、ctyK基因(47.75%)和ces基因(1.50%)。溶血性基因在疾病相关标本中的携带率比环境监测标本高(χ2=8.230,P<0.01),其余基因携带率则在两类标本中无统计学差异。环境监测标本中,土壤的溶血性基因携带率高于米粉和奶粉(χ2=15.071,P<0.01),非溶血性基因和entFM基因的携带率则低于后两者,检验值分别为(χ2=9.603,P<0.05)和(χ2=21.634,P<0.01)。结论 蜡样杆菌毒力基因在不同标本中的分布,尤其是毒力基因数目和溶血性基因在疾病相关标本中较高的携带特点,为研究蜡样杆菌的致病性提供了一定的参考依据,具有一定的临床意义。

In order to investigate the distribution of virulence genes of Bacillus cereus in different types of specimens and evaluate the potential risk, we detected 11 virulence genes including genes encoding enterotoxin( hblC, hblD, hblA, hblB, nheA, nheB, nheC, entFM, bceT and cytK ) and voitoxin(gene ces ) with PCR method in 333 Bacillus cereus strains collected from food(packaged rice flour and dried milk), soil and clinical specimens(rice and cold noodles associated with food poisoning and patients). Analysis of variance and Chi square test were performed. Results showed that the average gene numbers of tested strains were 5.97, there were 8.75 genes from patients, 8.20 from cold noodles, 7.13 from rice, 6.22 from soil, 5.78 from packaged rice flour and 5.71 from dried milk, respectively. Both the numbers of virulence gene from patients and cold noodles were higher than that from dried milk and the differences were significant. The total carrying rates of genes for nhe, entFM, bceT, hbl, cytK and ces were 89.19%, 79.88%, 49.85%, 48.35%, 47.75% and 1.50%, respectively, in the 333 studied strains. The carrying rates of gene hbl from clinical specimens was higher than that from other specimens(χ 2=8.230, P <0.01). However, the differences for other genes were not significant between the two kinds of specimens. Comparison of intra-group differences showed that the rate for gene hbl from soil was higher than that from dried milk and rice flour. The rates for genes nhe and entFM from soil were lower than the latter. This study showed us the distribution of virulence genes of Bacillus cereus in several kinds of specimens. The higher virulence gene numbers and carrying rates of the gene hbl in clinical specimens suggested that the haemolytic enterotoxin might play a role in disease progression.