Salmonella Minnesota Isoladas da Cadeia de Produção Avícola: Genes de Virulência, Formação de Biofilmes e Inibição com Biocidas

Abstract

The Salmonella genus stands out for its high prevalence among the microorganisms most often found in outbreaks of foodborne diseases. Among the serovars, S. Minnesota, has been showing a constant growth in the number of isolations along the entire Brazilian poultry production chain and also in the European Union and the United States, which demonstrates its importance and the necessity to investigate the causes of its emergence to establish more effective control measures. The thesis was divided in three chapters, the first referring to the general considerations of the topics covered in the other chapters. The second chapter aimed to evaluate the presence of virulence genes and environmental adaptation in 20 strains of S. Minnesota, isolated in the years 2009, 2010 and 2014, in broiler slaughter plants of two Brazilian companies, in order to infer the risk potential that they represent, and also to establish the phylogenetic relationship among isolates. The presence of genes associated with apoptosis (avrA), oxidative stress (sodC), invasion (invA), adhesion-related (agfA), biofilm formation (lpfA) and quorum-sensing process (luxS) was evaluated. The virulence profiles generated showed that the strains are potentially pathogenic and PFGE showed great genetic diversity, with 14 pulse types, three of them with homology greater than 80%. The third chapter aimed to determine the Biofilm formation index (IFB) for the 20 strains of S. Minnesota at three temperatures (4ºC / 25ºC / 36ºC), as well as to investigate the action of the tallowing biocidal agents: 1% chlorhexidine, 1 % sodium hypochlorite and 0.8% peracetic acid in inhibition of formed biofilms. The results demonstrated that the ability of S. Minnesota to produce biofilm at different temperatures is variable and strain dependent, but temperatures of 25 and 36ºC are more favorable to their formation. All strains were resistant to 1% sodium hypochlorite whereas the use of peracetic acid and chlorhexidine demonstrated the same efficiency in reducing counts of resistant strains. The presence of tolerant strains to the biocides tested is of concern and suggests a possible expression of genes related to oxidative stress and / or exposure to sublethal concentrations in the poultry production environment, representing a real potential for the development of adaptation mechanisms. The inclusion of stricter measures to prevent the installation and to ensure the removal of S. Minnesota biofilms, coupled with monitoring protocols, should be a strategy in the poultry industry to ensure the safety of the food produced.

Keywords: Biocides, Biofilms, Broiler, Gene, PFGE, Salmonellosis.