Comparison of infection of different cell lines by uropathogenic Escherichia coli

Studying the interaction between uropathogenic Escherichia coli (UPEC) and uroepithelial cells is important in elucidating the pathogenesis of urinary tract infection. In this study, the African green monkey kidney cells (Vero), human kidney carcinoma cells (Ketr-3) and bladder carcinoma cells (EJ) were infected by UPEC132, a clinical strain isolated from Tianjin, China, and were compared for their capacities to allow the adherence and invasion by this strain. The results revealed that all these cell lines could be attached and invaded by UPEC132. The adherence rates for Vero, Ketr-3 and EJ cells were (49.20 ± 7.55)%, (55.22 ± 4.09)% and (73.20 ± 5.26)%, respectively, and invasion frequencies were (2.61 ± 0.32)×10⁻³, (3.00 ± 0.34)×10⁻³ and (3.25 ± 0.20)×10⁻³, respectively. The statistical analysis showed that the adherence rate for EJ cells was significantly higher than those for the other two cell lines (P<0.05), and the invasion frequencies for EJ and Ketr-3 cells had no statistical differences (P>0.05) but were higher than that for Vero cells (P<0.05). Three cell lines were detected for the receptors for P pili of UPEC by using indirect immunofluorescence. The results showed that receptors existed on the surfaces of all cell lines, and the highest distribution was found on the surface of EJ cells. Additionally, the invasion of EJ cells by recombinant UPEC132/pSELECT-GFP could be directly visualized using confocal microscopy. These data strongly implicated that EJ cells could be more easily infected by UPEC132 than the other cells, and thus could serve as a good experimental target for further investigation of UPEC infection. Supported by the National Natural Science Foundation of China (Grant No. 30470096) and Specialized Research Fund for the Doctoral Program of Higher Education (Grant No. 20070062010) Contributed equally to this work