B-193. Virulence and Plasmid Profile of O113:H21 Escherichia coli Strains Isolated from Different Sources in Brazil

L. F. Santos1, K. Irino2, T. M. I. Vaz2, R. M. Silva1, B. E. C. Guth1;
1Univ. Federal de São Paulo, São Paulo, BRAZIL, 2Inst. Adolfo Lutz, São Paulo, BRAZIL.

Shiga toxin-producing Escherichia coli (STEC) strains of serotype O113:H21 have been increasingly associated with human infections and hemolytic uremic syndrome. Highly pathogenic STEC is known to produce different Stx types and often harbor large plasmids coding for specific virulence determinants. These additional factors may take part in the pathogenesis of STEC diseases and contribute to severe clinical outcomes. In the present study several virulence markers and the plasmid profile of 37 O113:H21 E. coli strains isolated in different Brazilian states were analysed. Thirty four strains were from animals and food sources and harbored stx; three strains, lacking stx, were isolated from human infections. Eight chromosomal (eae, lpfAO113, iha, cdt-V, cnf1, cif, astA and espI) and eight plasmid (ehxA, subAB, katP, espP, epeA, cnf2, toxB and saa) genes were investigated by PCR. The occurrence of large plasmids compatible with the already described STEC megaplasmid was analyzed in agarose gels after extraction of plasmid DNA by the alkaline lyses method. The most prevalent gene found was that encoded by the lpfO113 operon, lpfAO113, which occurred in all strains, followed by iha, present in 73% of the strains. Genes ehxA, subAB, espP and saa were equally found in 62% of the strains, and the sequences related to epeA, espI, astA and cdt-V could be identified in 59%, 33%, 30% and 19% of the strains respectively. The eae, toxB, cnf1, cnf2, cif and katP genes were not detected. Based on the distribution of the different virulence markers among the studied strains ten different profiles were identified. The profile ehxA, subAB, epeA, espP, lpfAO113, iha, saa, associated or not to cdt-V was the most prevalent. Twenty-five of the 37 strains had one or two high molecular mass plasmid bands (> 70 kDa), however only 22 strains harboring large plasmids also presented plasmid genes sought by PCR. These results demonstrated that O113:H21 E. coli strains from different sources in Brazil display distinct virulence features, and that non-human O113:H21 isolates may have the same pathogenic behavior as the classical EHEC serotype O157:H7.