Cumulative acquisition of pathogenicity islands has shaped virulence potential and contributed to the emergence of LEE-negative Shiga toxin-producing Escherichia coli strains

DEL CANTO, F; VELASCO, J; PADOLA NL; SALAZAR, JC; OÑATE A; BLANCO J; CONTRERAS C; PUENTE, JL; MONTERO, D; FRANZ E; VIDAL, R; COLELLO R; MARTÍN C; RASKO, D; SCHEUTZ F

Emerging Microbes & Infections

Informa UK Limited, trading as Taylor & Francis Group on behalf of Shanghai Shangyixun Cultural Communication Co., Ltd

Lugar: Shanghai; Año: 2019 vol. 8 p. 486 - 502

2222-1751

Shiga toxin-producing Escherichia coli (STEC) are foodborne pathogens causing severe gastroenteritis, which may lead tohemolytic uremic syndrome. The Locus of Enterocyte Effacement (LEE), a Pathogenicity Island (PAI), is a majordeterminant of intestinal epithelium attachment of a group of STEC strains; however, the virulence repertoire of STECstrains lacking LEE, has not been fully characterized. The incidence of LEE-negative STEC strains has increased inseveral countries, highlighting the relevance of their study. In order to gain insights into the basis for the emergenceof LEE-negative STEC strains, we performed a large-scale genomic analysis of 367 strains isolated worldwide fromhumans, animals, food and the environment. We identified uncharacterized genomic islands, including two PAIs andone Integrative Conjugative Element. Additionally, the Locus of Adhesion and Autoaggregation (LAA) was the mostprevalent PAI among LEE-negative strains and we found that it contributes to colonization of the mice intestine. Ourcomprehensive and rigorous comparative genomic and phylogenetic analyses suggest that the accumulativeacquisition of PAIs has played an important, but currently unappreciated role, in the evolution of virulence in thesestrains. This study provides new knowledge on the pathogenicity of LEE-negative STEC strains and identifies molecularmarkers for their epidemiological surveillance.