Serotype distribution of plasmid-encoded virulence profiles, and identification of espP and subAB alleles in verotoxigenic Escherichia coli

SANSO, A. M.; BUSTAMANTE, A.V.; FRANCI, T.; GONZ¨¢LEZ, JULIANA; CADONA, J.S.; LUCCHESI, P.M.A.

British Microbiology Research Journal

SCIENCEDOMAIN international

Año: 2014 vol. 5 p. 396 - 404

Aims: This study was designed to characterize verotoxigenic Escherichia coli (VTEC), importantfood-borne pathogens, in relation to virulence genes found in large plasmids harboured by disease associatedstrains. Our aim was to detect these genes and possible combinations of them, and toestablish if some kind of relationship exists between these profiles and different serotypes.Study Design: Amplification of genes and allelic variants by PCR.Place and Duration of Study: Laboratorio de Inmunoqu¨ªmica y Biotecnolog¨ªa (FCV-UNCPBA,Argentina), between June 2010 and July 2013.Methodology: 208 VTEC isolates belonging to 49 serotypes were characterized for the presenceof plasmid-encoded genes: epeA (serine-protease), espP (extracellular serine protease) and itsvariants, katP (periplasmic catalase-peroxidase), stcE (zinc metalloprotease) and subA (subtilasecytotoxin) and its variants.Results: The most frequently detected gene was espP (87%), followed by ehxA (47%), saa (20%)and katP (17%), whereas epeA, subA and stcE ranged from 7 to 12%. Taking into account thesegenes, twelve profiles were observed, ranging from the presence of zero to five of the genes. Someserotypes presented only one plasmid profile whereas others, such as O20:H19, showed up to fourdifferent profiles. Functional differences have been previously found among EspP subtypes, andwe found that several VTEC isolated from bovines or foods contained the espP alfa, which is one ofthe alleles possibly associated with severe human disease. Considering subtilase cytotoxin genesubtypes, only subAB1 was identified.Conclusion: Our results show that VTEC strains can possess different combinations of plasmidencodedvirulence genes and even strains belonging to the same serotype can differ in relation totheir plasmid genetic composition. In relation to allelic variants, LEE-positive serotypes showed forespP gene the allele alfa or the ¦Ã, and the detected subAB allele differed from the prevalent allelicvariant subAB2 carried by strains circulating in sheeps and humans in European countries.