肠致病性大肠杆菌的生物膜形成对致病岛基因的影响

Effect of biofilm formation by enteropathogenic Escherichia coli under different pH values on expression of pathogenic island gene espA

目的研究不同p H值条件对肠致病性大肠埃希菌生物膜形成能力及对致病岛基因的影响。方法将2株EPEC菌株（E11313和E11435）分别接种于p H值为7、9和11的LB培养基,用结晶紫染色半定量法检测2株菌株产生物膜能力,观察产生物膜菌株及非产生物膜菌株生物膜形成的差异,将2株菌株产生的生物膜溶解,提取总RNA,定量PCR检测不同p H浓度的生物膜与致病岛基因Esp A表达水平的关系。结果 E11435为生物膜阳性菌株,E11313为生物膜阴性菌株,p H为7~9之间,生物膜的形成变化不大,当p H值=11时,菌株形成生物膜更容易,E11435菌株形成的生物膜可影响EPEC致病岛Esp A基因的表达,且当p H=11时,Esp A表达水平明显提高（P〈0.05）。结论碱性环境可促进肠致病性大肠杆菌生物膜的形成。生物膜阳性肠致病性大肠杆菌可显著提高致病岛Esp A基因的表达水平。

Objective To investigate the effects of biofilm formation ability of enteropathogenic E.coli（EPEC）.onpathogenic island gene esp A under different p H values. Methods Two EPEC strains（E11313 and E11435） were inoculatedLB medium at a p H of 7, 9 and 11, respectively, and their biofilm production capacities were detected with crystal violetstaining semi-quantitative method, the differences of biofilm formation between strains that could produce biofilm and strainsthat could not produce biofilm were observed, the two strains that could produce biofilm were dissolved, total RNA wasextracted, quantitative PCR was used to detect the relationships between biofilm with different p H concentrations andexpression levels of Esp A pathogenic island gene. Results E11435 were biofilm- positive strains, E11313 were biofilm-negative strain, when the p H value was between 7 and 9, the formation of biofilm were no statistically significant differences.While when the p H was increased to 11, biofilm formation was easier. The biofilms formed by E11435 might affect theexpression of pathogenic island Esp A genes of EPEC, and with the increase of p H values, Esp A expression levels weresignificantly increased（P〈0.05）. Conclusions The basic conditions can affect the biofilm formation of enteropathogenic E.coli, biofilm-positive enteropathogenic E.coli can increase the expression level of pathogenic island Esp A protein.