Distribution of serine protease espP subtypes among verotoxigenic Escherichia coli isolated in Argentina

Abstract

Introduction and Objectives: Infections by verotoxigenic Escherichia coli (VTEC) range from mild, self-limiting diarrhea to severe diseases such as hemorrhagic colitis (HC) and hemolytic uremic syndrome (HUS). Ruminants and derived foods are the main sources of human infections. Epidemiologic studies have shown that virulence factors other than verotoxins may also contribute to its pathogenic- ity in humans, including the plasmid-encoded serine protease EspP. EspP belongs to the serine protease autotransporters of Enterobacte- riaceae (SPATE) family, and contributes to the adherence to bovine primary rectal cells and colonization of the bovine intestines. More- over, degradation of human coagulation factor V via EspP could contribute to the mucosal hemorrhage observed in HC patients. Five espP alleles with different proteolytic activities have been identified and some authors have demonstrated that subtype a is associated with highly pathogenic serogroups. Material and Methods: Since espP has been found in a high preva- lence and there are few data about de distribution of espP subtypes among VTEC strains from different origins, our aim was to investi- gate the ocurrence of the subtypes a, b, c, d, and e in espP-positive Argentine strains. Determination of espP alleles was done by PCR in 182 isolates belonging to 44 serotypes from cattle, food and humans. Results: Some serotypes harbored only one espP subtpype whereas others presented more than one allele. The a subtype was found in serotypes O26:H11, O38:H39, O103:NM, O103:H2, O118:H16, O145:NM, O146:NM, O157:H7 and O177:NM, whereas b subtype in O8:H16, O20:H19, O39:H49, O79:H19, O113:NM, O113:H21, O117:H7, O141:H8, O174:H21, O178:H19, O185:H7 and several ONT strains with different H antigen. Conclusions: Subtyping of the espP gene revealed an association among O serogroups and particular espP subtype(s). Also, despite that in previous studies espP a was present particularly in isolates from HUS patients, we found that some VTEC strains isolated from reservoir animals or foods also contained this espP allele. Particu- larly interesting is the observation that serogroup O103, considered to be highly pathogenic and reported in previous studies as negative for espP, resulted espP+ and carried the allele a.