Co-infection with EHEC and C. albicans in vitro enhances invasion and tissue damage of enterocytes induced by C. albicans

Abstract

Objective To investigate, in vitro, the co-infection of Caco-2 cells (epithelial cells of intestinal mucosa) with Candida albicans and Enterohemorrhagic escherichia coli (EHEC). Methods The ability of both species to invade the Caco-2 cells was evaluated by inverted microscopy. Damage to Caco-2 cells was evaluated by measuring lactate dehydrogenase (LDH) activity. C. albicans virulence gene expression (ALS3, PLB1 and SAP4) was evaluated by quantitative real-time polymerase chain reaction (qRT-PCR). Results Compared to simple infections with C.albicans alone, a co-infection invaded Caco-2 cells more rapidly, and C. albicans tended to proliferate more easily presenting in cluster shape of distribution. In addition, the LDH activity in the co-infection group (group 3) was the highest compared to groups 1, 2, 4 and 5, (F values of 14.48, 5.48, 11.74 and 3.45 respectively; all P <0.05); There was no significant difference in LDH activity found between the secondary fungous infection group (group 5) and the EHEC infection group (group 2) (F=2.03, P=0.54) or between the secondary bacterial infection group (group 4) and the Candida albicans infection group (group 1) (F=2.74, P=0.11). The LDH activities in groups 2 and 5 were significantly higher than that in groups 1 and 4 (all P <0.05). In addition, an up-regulation of toxicity-related genes (PLB1 and SAP4) were detected. The expression of PLB1 was higher in group 3 than that in group 1(P=0.014 3)and SAP4 was higher in groups 3 and 5 than that in group 1(P=0.027 2, P=0.001 8, respectively). Conclusions Using Caco-2 cells for an infection model, this study demonstrated that co-infecting in vitro enterocytes with C.albicans and EHEC enhanced the invasiveness and tissue damaging effects of C.albicans. Key words: Enterohemorrhage escherichia coli; Candida albicans; Co-infection; Invasion; Tissue damage; Inverted microscope; LDH; qRT-PCR