Effects of a non-toxin producing E. coli O157:H7 and Stx2 on a human microvascular endothelial cell line (HMEC-1)

GABRIEL GONDOLESI; CRISTINA IBARRA; FRANCISCO PATIN; MARIA MARTA AMARAL; NICOLAS GARIMANO; HORACIO REPETTO

Capital Federal

Congreso; Reunión Conjunta de Sociedades de Biociencia 2017; 2017

Shiga toxin (Stx)-producing Escherichia coli (STEC) strains are responsible of bloody diarrhea (hemorrhagic colitis) and hemolytic uremic syndrome (HUS). Hemorrhagic colitis (HC) is a major complication of HUS that sometimes appears prior to the detection of characteristic HUS findings (Rahman et al, 2012). The patients with HC showed severe renal and neurologic disease. It is believed that HC may be the result of compromise of local blood vessels and that could be the cause of the most severe HUS complications. E. coli O157:H7 is, by far, the most prevalent serotype associated with HUS and Stx2 is the major virulence factor associated for the more severe symptoms of the infection. Our aim was to study the effects of a non-toxin producing E. coli O157:H7 and Stx2 on HMEC-1 (an immortalized human microvascular endothelial cell line) in order to better understand the means by which STEC induce HC. We examined cell viability after 4 h of incubation with purified Stx2, a mutant of E. coli O157:H7 lacking stx2 gene (O157:H7∆stx2), E. coli HB101 (an E. coli strain lacking adhesive capabilities), and filtered O157:H7∆stx2 supernatant (SN), which was used to assess basal cytotoxicity. Cells were grown in 96-well culture plate and viability was measured by neutral red uptake after 24 h under growth-arrested condition. We have also evaluated bacterial adhesion by colony-forming unit (CFU/ml) assay and Giemsa-staining direct observation. We observed cytotoxic effects induced by Stx2 and by O157:H7∆stx2 (CD50 0,01 ug/ml and 2E08 CFU/ml respectively). Moreover, significant bacterial adhesion was found with O157:H7∆stx2 compared with the other strain (P