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Search for new genetic markers and multi locus sequence typing (MLST) of atypical enteropathogenic and Shiga toxin-producing Escherichia coli strains isolated in Brazil

Grant number: 17/00411-1
Support type:Regular Research Grants
Duration: June 01, 2017 - November 30, 2019
Field of knowledge:Biological Sciences - Microbiology
Principal Investigator:Luis Fernando dos Santos
Grantee:Luis Fernando dos Santos
Home Institution: Instituto Adolfo Lutz (IAL). Coordenadoria de Controle de Doenças (CCD). Secretaria da Saúde (São Paulo - Estado). São Paulo , SP, Brazil
Assoc. researchers:Beatriz Ernestina Cabilio Guth ; Rodrigo Tavanelli Hernandes

Abstract

Enteropathogenic (EPEC) and Shiga toxin-producing Escherichia coli (STEC) represent important pathotypes among E. coli strains causing enteric infections. EPEC is divided in typical and atypical. Typical EPEC by definition is characterized by the presence of the eae and bfp genes, while EPEC-a harbors eae but are devoid of bfp, and both, typical and atypical EPEC, lack stx gene responsible for the production of Shiga toxins (Stx). STEC strains are defined by the presence of stx, and may also have eae. Evidence has shown that strains identified as EPEC-a (eae +, bfp-, stx-) may actually represent clones that were originally STEC and lost the stx, since this gene is found in the genome of bacteriophages and therefore can be lost by phage excision in response to various stimuli. The analysis of EPEC-a strains isolated in Germany by Multi Locus Sequence Typing (MLST) confirms this hypothesis, since many of the Sequence Types (ST) identified in the EPEC-a strains studied are characteristic of STEC. Incorrect identification of EPEC-a and STEC may have negative clinical, epidemiological and even economic implications. Therefore, recent studies have proposed the use of new genetic markers for differentiation of EPEC-a strains associated with the EPEC pathotype, from those that could have underwent stx excision. In particular, some genes belonging to the genomic island OI-57, and genes espK, etpD, espM, espN and espV which are highly specific to the STEC pathotype, have been shown to be quite promising. Additionally, analyzes of the so-called Clustered and Regularly Interspaced Short Palindromic Repetitions (CRISP), which have high seropathotype specificity, have been used with satisfactory results in studies conducted in France and in other countries. There are no studies in Brazil describing the occurrence of the mentioned markers nor the Sequence Types of EPEC-a and STEC strains isolated from human and non-human sources in our environment. Thus, the objective of this study is to investigate the occurrence of genes associated to the OI-57 island, and genes espK, etpD, espM, espN and espV, and also perform MLST typing of strains of EPEC-a and STEC belonging to different serotypes , isolated from cases of human infection and hemolytic uremic syndrome (HUS) in Brazil. Sites of insertion of stx gene into the bacterial chromosome will also be investigated. In addition, the occurrence of a specific allelic form of the arcA gene, which is found only in STEC strains of serotype O26: H11 and its derivative clones that have undergone stx gene excision will also be investigated. The results to be obtained may demonstrate the existence of new targets for the development of laboratory diagnostic strategies for STEC and EPEC-strains, such as molecular kits, based on these genetic markers. Such results will also be of paramount importance for advances in the knowledge on the epidemiology of EPEC-a and STEC in our settings, thus contributing to a more effective management of the diseases transmitted by these pathogens. (AU)