Differential Cytotoxic Effects of Cell-Free Supernatants of Emerging Pathogens Escherichia albertii and Escherichia fergusonii on Four Cell Lines Reveal Vero Cells as a Putative Candidate for Cytotoxicity Analysis

<i>Escherichia albertii</i> and <i>Escherichia fergusonii</i> are recognized as emerging pathogens with zoonotic potential. Despite their increasing importance, there is a paucity of data on the cytotoxicity of these two pathogens. Therefore, in the present study, we investigated the cytotoxic potentials of the cell-free supernatants from 10 <i>E. albertii</i> and 15 <i>E. fergusonii</i> isolates for their cytotoxic effects on four different cell lines (CHO, Vero, HeLa, and MDCK). All <i>E. albertii</i> isolates (100%) and all but one <i>E. fergusonii</i> (93.33%) were cytotoxic. <i>E. albertii</i> isolates produced similar cytotoxicity titres across the cell lines, whereas the Vero cell was found to be the most sensitive to toxins produced by <i>E. fergusonii</i> (<i>p</i> < 0.05), followed by HeLa and CHO cells. MDCK was the least sensitive cell line to <i>E. fergusonii</i> toxins (<i>p</i> < 0.05). PCR detection of cytotoxicity-associated genes (<i>cdtB</i>, <i>stx1,</i> and <i>stx2</i>) indicated uniform possession of <i>cdtB</i> gene by all <i>E. albertii</i> isolates, while <i>stx1</i> and <i>stx2</i> genes were harboured neither by <i>E. albertii</i>, nor <i>E. fergusonii</i>. Taken together, our results provided experimental evidence of the cytotoxic effects of these two emerging pathogens, and Vero cells were identified as an optimal candidate to study the cytotoxic effects of <i>E. albertii</i> and <i>E. fergusonii</i>.