3株被膜态产志贺毒素大肠杆菌产志贺毒素能力的分析

Analysis of Shiga toxin-producing ability of 3 biofilm strains of Shiga Toxin-producing Escherichia coli

摘要:

为了解食源性产志贺毒素大肠杆菌(Shiga toxin-producing Escherichia coli, STEC)的菌株特征及潜在致病性,分析其在被膜状态下产志贺毒素能力的变化情况。采用传统PCR技术扩增stx基因亚型,菌株1携带stx1c+stx2d亚型,菌株2携带stx1+stx2f亚型,菌株3携带stx2e亚型。多位点序列分型(MLST)结果显示3株菌株亲缘关系较远,具有遗传多样性。分别利用结晶紫染色试验和Vero细胞毒性试验探究菌株在4、10、25和37 ℃下被膜形成能力和产志贺毒素能力。结果表明,温度显著影响被膜形成能力和产志贺毒素能力,37 ℃时3株菌株的被膜形成能力和产志贺毒素能力最强。Vero细胞毒性试验结果表明,4个温度条件下,菌株2产志贺毒素能力最弱。菌株3在4个温度条件下均表现强被膜形成能力和产志贺毒素能力,尤其在4和10 ℃时,菌株3较其他2株菌被膜形成能力强。我国市场零售肉存在STEC污染,部分菌株具有潜在致病性,尤其是强被膜形成能力、产志贺毒素能力菌株的发现,应加强对食品加工处理过程中STEC的监测。

Abstract:

Shiga toxin-producing Escherichia coli (STEC) is a zoonosis and food-borne pathogenic bacterium. It is necessary to understand its characteristics and potential pathogenicity and analyze the production ability of Shiga toxin (Stx) in the biofilm state. The traditional PCR was performed to amplify the stx variant gene subtype. The results showed that strain 1 carried stx1c+stx2d subtype, strain 2 carried stx1+stx2f subtype, and strain 3 carried stx2e subtype. The results of multilocus sequence typing (MLST) showed that the three strains were relatively distantly related and possessed genetic diversity. The crystal violet staining test and the cytotoxicity test of Vero cell were used to explore the biofilm-forming ability and Stx-producing ability at 4 ℃, 10 ℃, 25 ℃, and 37 ℃. It showed that temperature significantly affected the biofilm-forming ability and Stx-producing ability. All STEC strains had the strong ability of biofilm formation and Stx production at 37 ℃. The results of the cytotoxicity test of Vero cell showed that strain 2 had the weakest Stx-producing ability under the four different temperature conditions and strain 3 showed strong biofilm-forming ability and Stx-producing ability. Especially at 4 ℃and 10 ℃, strain 3 had the strongest biofilm-forming ability compared to strain 1 and stain 2. Retail meat in China is contaminated with STEC which could be potentially pathogenic. Especially with the discovery of strains with strong biofilm-forming ability and Stx-producing ability, we should strengthen the monitoring of STEC during food processing.