Perfil de genes de virulência e diversidade clonal de Escherichia coli produtora de toxina Shiga (STEC) e enteropatogênica atípica (aEPEC) do sorotipo O26: H11 / Virulence gene profile and clonal diversity of Shiga toxin-producing Escherichia coli (STEC) and atypical enteropathogenic (aEPEC) serotype O26: H11

RESUMO

O sorotipo O26H11 associado às aEPEC e STEC tem sido frequentemente implicado com doenças entéricas em diversos países. Análises comparativas de cepas O26H11 STEC e aEPEC de vários países indicam que as aEPEC O26H11 representam clones que perderam os genes stx através da excisão fágica. No Brasil, o isolamento de aEPEC O26H11 de casos de infecção humana é frequente, sendo este um dos mais importantes sorotipos de aEPEC em nosso meio. O objetivo deste estudo foi investigar e fazer uma análise comparativa sobre a ocorrência de vários genes de virulência, alguns deles altamente específicos para o patotipo STEC, em cepas O26H11 STEC e aEPEC, além de avaliar a diversidade clonal através das técnicas de PFGE e sequenciamento MLST. Oito das 10 cepas STEC apresentaram o genótipo stx1a, enquanto duas cepas apresentaram stx2a. Este é o primeiro relato sobre a ocorrência de STEC O26H11 albergando o genótipo stx2a no Brasil. Os genes plasmidiais ehxA, katP, espP e toxB foram encontrados em 8 (80%), 7 (70%), 8 (80%) e 8 (80%) das STEC. Todas as STEC abrigaram os genes efa, escN, nleB, nleE, sen, z2098, z2099, z2121, ureD e terE. Os genes espK e espM1 foram encontrados em igual frequência. Dentre as aEPEC, todas foram positivas para os genes efa, escN, nleB, nleE, sen e z2121. Os genes ehxA, espP, espM1, iha, katP, toxB, z2098, z2099, espK, espV, espN, ureD e terE estiveram presentes em 25 (66%), 25 (66%), 35 (92%), 31(82%), 16 (42%), 18 (47%), 26 (68%), 26 (68%), 31 (82%), 13 (34%), 19 (50%), 26 (68%) e 30 (79%) das cepas, respectivamente. O gene astA foi encontrado em apenas três (8%) aEPEC e nenhuma das cepas estudadas...(AU)

ABSTRACT

The O26 H11 serotype which is associated with pathotypes aEPEC and STEC, is implicated with enteric diseases in several countries. Comparative analyzes of O26H11 STEC and aEPEC strains from several countries indicated that many aEPEC strains represent STEC clones that lost the stx genes through phage excision. The aim of this study was to investigate the occurrence of several virulence genes, some of which highly specific for the STEC pathotype, in strains O26H11 STEC and aEPEC, and to evaluate clonal diversity employing of PFGE and MLST aproches. Eight of the 10 STEC strains presented stx1a subtype, while two strains presented stx2a. This is the first report on the occurrence of STEC O26 H11 harboring the stx2a genotype in Brazil. The plasmidial genes ehxA, katP, espP and toxB were found in 8 (80%), 7 (70%), 8 (80%) and 8 (80%) of STEC. All STECs harbored the efa, escN, nleB, nleE, sen, z2098, z2099, z2121, ureD and terE genes. The espK and espM1 genes were found at the same frequency. Among aEPEC, all were positive for the efa, escN, nleB, nleE, sen and z2121 gene. The genes ehxA, espP, espM1, iha, katP, toxB, z2098, z2099, espK, espV, espN, ureD and terE were present in 25 (66%), 25 (66%), 35 (92%), 31 ( 82%), 16 (42%), 18 (47%), 26 (68%), 26 (68%), 31 (82%), 13 (34%), 19 (50%), 26 (68%) ) and 30 (79%). The astA gene was found in only three (8%) aEPEC and none of these strains showed the presence of cdt-V, etpD and pagC. All STECs presented CRISPR sequences, being C+D CRISPR types. Among the aEPEC in addition to these two polymorphisms associated with CRISPR sequences, type E was also found. PFGE typing revealed a wide genetic diversity both between STEC and aEPEC. MLST typing was performed on 24 strains of aEPEC and STEC, ten STECs and 14 aEPEC, but not all strains had a valid ST through the Enterobase bank, only 18 strains presented ST, and all these ST belonged to the clonal complex 29. ST21 and ST29 occurred equally, in four STECs each. Among the aEPEC, two were ST21 and eight belonged to ST29. Most strains of aEPEC O26 H11 in our study demonstrated several characteristics compatible with STEC and are therefore derived from this pathotype. (AU)