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.