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Molecular study of the resistance to lytic bacteriophages in pathogenic strains of Salmonella enterica subs. enterica serovar Enteritidis

Grant number: 11/11761-7
Support type:Scholarships in Brazil - Doctorate
Effective date (Start): June 01, 2012
Effective date (End): July 31, 2015
Field of knowledge:Agronomical Sciences - Veterinary Medicine - Animal Pathology
Principal Investigator:Paulo Eduardo Martins Ribolla
Grantee:Letícia Amaral Nogueira Alonso
Home Institution: Instituto de Biociências (IBB). Universidade Estadual Paulista (UNESP). Campus de Botucatu. Botucatu , SP, Brazil

Abstract

Salmonella Enteritidis is a pathogen that belongs to the Enterobacteriaceae family and is often related to infections transmitted by food in humans, especially in children, elderly and immunosuppressed patients. The importance of this microorganism is because its significant prevalence with worldwide distribution in lots of poultry, leading to serious implications for public health. Effective control of salmonellosis is a challenging because its involves a complex animal handling and treatment with antibiotics that do not guarantee the elimination of infection. The use of lytic bacteriophages against bacterial infections (phagetherapy) meets a demand for alternatives to the conventional antimicrobial treatment. However, the literature has reported the emergence of bacterial resistance to some lytic bacteriophages, such as Salmonella sp. There are several mechanisms of bacterial resistance to phages, such as prevention of adsorption, blocking the injection of phage DNA, restriction-modification, abortive infection and most recently described in the literature, the CRISPR system / CAS acquired immunity. Thus, this project aims to study in a molecular level the bacterial resistance of lytic phages isolated from pathogenic strains of Salmonella enterica subs. enterica serovar Enteritidis (SE). Two mechanisms have been chosen: the CRISPR system / CAS and blocking of phage adsorption via LPS. Preliminary results showed that SE resistant strains to lytic phages have a greater number of CRISPR spacers than sensitive strains. Phylogenetic analysis of cas1, cas2 and cas3 gene sequences grouped SE strains into two major clades, a branch sensitive to phages and another branch containing mostly resistant strains. The two most different strains in the tree were one of the most phage resistant. Interestingly, these two strains also have a higher number of CRISPR spacers. The genes analysis LPS related showed that among the genes investigated, rfaC, rfaH, cpsG, manB and ManC genes were correlated with resistance. These results suggest possible candidates for molecular markers of resistance to phages in Salmonella Enteritidis. (AU)