膀胱上皮细胞清除胞内大肠杆菌

目的:了解大肠杆菌与膀胱上皮细胞的相互关系,观察大肠杆菌在人膀胱上皮细胞株T24中的动态变化。方法:采用大肠杆菌标准株K12和大肠杆菌临床分离株299侵袭T24细胞,并用庆大霉素杀死细胞外的细菌,分别于细菌侵袭细胞后的4、24及48 h用TritonX-100裂解细胞,释放出细胞内的活细菌,用平板菌落计数法计数胞内活菌数。结果:两株大肠杆菌在T24细胞内都不能生长,随着时间的推移,细胞内大肠杆菌活菌数量呈不断减少趋势。24 h细胞内活菌数下降为4 h活菌数的15%。48h细胞内活菌数进一步减少。结论:膀胱上皮细胞清除进入细胞内的大肠杆菌,这可能是泌尿道天然免疫防御的一个重要防御机

Clearance of intracellular Escherichia coli by human urinary epithelial cells

Objective:The epithelial tissues represent a first barrier of defense against invading bacterial pathogens.To understand the interaction between pathogenic agents and urinary epithelial cells,intracellular survival curve of Escherichia coli in human urinary bladder epithelial cell line T24 was assayed.Methods:Monolayers of T24 cells were grown to confluence in RPMI 1640 medium.Cells were incubated with Escherichia coli K12 and a clinical isolate 299(approximately 10 bacteria per epithelial cell) for 2 h.After the incubation of the T24 cells with Escherichia coli,gentamicin was added to kill extracellular bacteria and the T24 cells were lysed with Triton X-100 at 4,24,and 48 hours after the initial incubation.Viable intracellular bacteria were quantified by plating appropriate dilutions on LB agar plates.Results:After 24 h of incubation,the number of viable intracellular E.coli K12 decreased to 15% of the intracellular bacteria recovered after 4 h of incubation.Similarly,only 14% of the clinical isolate 299 bacteria recovered after 4 h of incubation were viable at 24 h and the intracellular bacteria continued to decline at 48 h.Conclusion:The reduction of bacterial viability over time suggests that urinary bladder epithelial cells have the ability to kill invading Escherichia coli.The clearance of intracellular bacteria by human urinary epithelial cells might represent an important mechanism of the host defense against urinary tract infection.