|1837-2||Genetic Analysis of the Enteroaggregative Escherichia coli Heat-Stable Enterotoxin (EAST1) Gene from Atypical Enteropathogenic Escherichia coli (EPEC) Strains|
|Autores:||Lucas E. P. Silva (UNIFESP - Universidade Federal de São Paulo) ; Isabel C. A. Scaletsky (UNIFESP - Universidade Federal de São Paulo) |
The enteroaggregative Escherichia coli heat-stable enterotoxin 1 (EAST1) gene is widely distributed among diarrheagenic E. coli strains. In this study, we examined the existence of EAST1 variants in atypical enteropathogenic Escherichia coli strains by PCR and sequencing. The PCR reaction was assayed with the primer set of EAST13a and EAST12b, and with the primer set of EAST11a and EAST11b. The primer sequence EAST13a is located 110 nucleotides upstream from the initiation ATG sequence of the EAST1 gene, and the primer sequence EAST12b is located 20 nucleotides downstream from the stop TGA sequence of the EAST1 gene. The primer set of EAST11a and EAST11b detects an internal fragment of the EAST1 gene. A total of 31 (20.1%) strains were positive in the PCR assay with both sets of primers, generating a 289-bp (for EAST13a and EAST12b) and 111-bp (for EAST11a and EAST11b) products. The PCR-positive strains were found more commonly (P < 0.05) in strains isolated from children with diarrhea. The sequence analysis of PCR products confirmed the presence of EAST1 gene sequence of enteroaggregative E. coli O42 strain. Other 22 (14.3%) strains were positive only in the PCR assay with the primer set of EAST13a and EAST12b. The sequences of the PCR products of 5 out 22 above mentioned strains revealed complete agreement with the EAST1 gene sequence of enterohemorrhagic E. coli O157:H7 strain (type 1 SHEAST). The sequencing of the 17 remaining PCR products is in progress. Comparison of the EAST1 gene sequences analyzed so far showed that 31 strains possessed O42-type EAST1 gene and five other strains possessed type 1 SHEAST. The 17 remaining strains which amplified a band of the expected DNA size with the primer set of EAST13a and EAST12b may carry another variant of EAST1 gene, and their sequences are under investigation.
Palavras-chave: EPEC, Atypical EPEC, EAST1