Characterization of the α-haemolysin determinant from the human enteropathogenic Escherichia coli O26 plasmid pEO5 |
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Authors: | Ylanna Kelner Burgos Karin Pries Antonio Fernando Pestana de Castro & Lothar Beutin |
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Institution: | National Reference Laboratory for Escherichia coli;(NRL-E. coli), Federal Institute for Risk Assessment (BfR), Berlin, Germany;and Departamento de Microbiologia, Instituto de Ciências Biomédicas II, Universidade de São Paulo,São Paulo, Brazil |
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Abstract: | The 157-kb conjugative plasmid pEO5 encoding α-haemolysin in strains of human enteropathogenic Escherichia coli (EPEC) O26 was investigated for its relationship with EHEC-haemolysin-encoding plasmids of enterohaemorrhagic E. coli (EHEC) O26 and O157 strains. Plasmid pEO5 was found to be compatible with EHEC-virulence plasmids and did not hybridize in Southern blots with plasmid pO157 from the EHEC O157:H7 strain EDL933, indicating that both plasmids were unrelated. A 9227-bp stretch of pEO5 DNA encompassing the entire α- hly CABD operon was sequenced and compared for similarity to plasmid and chromosomally inherited α- hly determinants. The α- hly determinant of pEO5 (7252 bp) and its upstream region was most similar to corresponding sequences of the murine E. coli α-hly plasmid pHly152, in particular, the structural α- hly CABD genes (99.2% identity) and the regulatory hly R regions (98.8% identity). pEO5 and α-hly plasmids of EPEC O26 strains from humans and cattle were very similar for the regions encompassing the structural α- hly CABD genes. The major difference found between the hly regions of pHly152 and pEO5 is caused by the insertion of an IS 2 element upstream of the hly C gene in pHly152. The presence of transposon-like structures at both ends of the α- hly sequence indicates that this pEO5 virulence factor was probably acquired by horizontal gene transfer. |
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Keywords: | Escherichia coli EPEC EHEC O26 α-haemolysin virulence plasmid |
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