Virulence repertoire of Shiga toxin-producing Escherichia coli (STEC): Stx subtypes and accessory virulence factors among isolates from the animal reservoir, and analysis of gene expression related to the adherence and biofilm formation processes

• Grant number: 15/10537-7
• Support Opportunities: Regular Research Grants
• Start date: September 01, 2015
• End date: February 28, 2018
• Field of knowledge: Biological Sciences - Microbiology - Biology and Physiology of Microorganisms
• Principal Investigator: Beatriz Ernestina Cabilio Guth
• Grantee: Beatriz Ernestina Cabilio Guth
• Host Institution: Escola Paulista de Medicina (EPM). Universidade Federal de São Paulo (UNIFESP). Campus São Paulo. São Paulo , SP, Brazil
• Associated researchers: Cecilia Matheus Guimarães ; Tânia Aparecida Tardelli Gomes do Amaral

Abstract

Shiga toxin-producing Escherichia coli (STEC) is an important foodborne pathogen associated with severe disease in humans as hemorrhagic colitis and hemolytic uremic syndrome (HUS). Although, most of the reported cases of HUS are assigned to O157:H7, more recently the prevalence of non-O157 serotypes responsible for serious diseases has also been highlighted, suggesting the importance of serotypes unable to cause attaching and effacing lesion (A/E). Ruminants, especially cattle, are the main natural reservoir of STEC. However, epidemiological surveys have indicated the presence of STEC in the gastrointestinal tract of other ruminants, such as sheep and goats. Thus, the transmission to man occurs mainly through the consumption of contaminated meat, but an increasing number of cases related to the consumption of vegetables have also been described. Shiga toxins play a central role in the pathogenesis of STEC diseases, but additional virulence factors also take part on this process. It is known that stx subtypes may be related to the severity of clinical symptoms. Therefore, there is growing interest in research on the occurrence of stx subtypes and genes related to accessory virulence factors, such as those related to autotransporter proteins or involved in iron uptake in STEC isolates devoid of A/E from the animal reservoir. Ability to form biofilms may enhance resistance of microorganisms to antimicrobial agents and sanitizers, allowing the maintenance of the bacteria on a surface or environment, which can lead to cross contamination in food production lines. Among the various STEC structures associated with biofilm formation flagella, fimbria Curli, autotransporter proteins as Cah, EhaA and the outer membrane protein OmpA can be highlighted. However, the correlation between these structures during biofilm formation by STEC strains needs to be analyzed. Therefore, this project intends to: a) evaluate the distribution of stx subtypes and accessory virulence genes in STEC isolates from the animal reservoir in order to identify the pathogenic potential of these strains; b) evaluate the expression of different structures and regulatory genes associated with adhesion and/or biofilm formation in an O157 STEC strain and mutants for cah and fliC genes. We intend with this approach to define a more specific and complete profile of pathogenic STEC strains circulating in our environment and to gain information on how structures related to adhesion and biofilm formation interact during this process considered to be multifactorial. (AU)