In Silico Prediction of Secreted Proteins in Shiga Toxin-Producing Escherichia coli: Identification of a Hydrolase as a Robust Genomic Marker

Shiga toxin-producing <i>Escherichia coli</i> (STEC) are major foodborne pathogens that can cause severe human disease. Identifying molecular markers associated with pathogenicity is essential to improve detection and to better understand virulence mechanisms. In this study, 35,828 <i>E. coli</i> genomes available in a public database were analyzed with the purpose of identifying STEC genes encoding proteins secreted to the outer membrane or into the extracellular space. The strains belong to six different sequence types (STs): ST442, ST297, ST1131, ST2217, ST2387, and ST2520. Comparative genomics allowed identification of 155 genes that were initially evaluated as potential virulence-associated candidates. Among these, a hydrolase-encoding gene showed a wide distribution and a significant association with STEC genomes versus non-STEC genomes (81.6% in the STEC group and 15.8% in the non-STEC group). The protein product is predicted to be released into the extracellular space and, according to examples in other bacterial pathogens, may contribute to STEC virulence. Altogether, our findings highlight this hydrolase as a relevant molecular marker that could complement current genetic screening schemes and support the design of novel control strategies against STEC infections.