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Open Access Highly Accessed Research article

Molecular analysis of subtilase cytotoxin genes of food-borne Shiga toxin-producing Escherichia coli reveals a new allelic subAB variant

Joschua Funk, Helen Stoeber, Elisabeth Hauser and Herbert Schmidt*

Author Affiliations

Department of Food Microbiology, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstraße 28, Stuttgart, D-70599, Germany

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BMC Microbiology 2013, 13:230  doi:10.1186/1471-2180-13-230

Published: 15 October 2013

Abstract

Background

The open reading frames of subAB genes and their flanking regions of 18 food-borne Shiga toxin-producing E. coli (STEC) strains were analyzed.

Results

All but one subAB open reading frames (ORF) were complete in all STEC strains. The subAB1 genes of nine STEC strains were located on large plasmids. The subAB2 allele (here designated subAB2-1), which was recently described by others to be present in the Subtilase-Encoding PAI (SE-PAI) was found in 6 STEC strains. A new chromosomal subAB2 variant, designated subAB2-2 was detected in 6 strains and was linked to a chromosomal gene hypothetically encoding an outer membrane efflux protein (OEP). Three STEC strains contained both subAB2 variants. DNA analysis indicated sequence conservation in the plasmid-located alleles and sequence heterogeneity among the chromosomal subAB2 genes.

Conclusions

The results of this study have shown that 18 subAB-PCR positive STEC strains contain complete subAB open reading frames. Furthermore, the new allelic variant subAB2-2 was described, which can occur in addition to subAB2-1 on a new chromosomal locus.

Keywords:
Subtilase cytotoxin; Shiga toxin-producing Escherichia coli; subAB; Deer; New variant; Complete open reading frames; Phylogenetic heterogeneity