Caracterização genômica e efeitos da exposição ao óleo essencial de menta em cepas epidêmicas de salmonella enterica

Abstract

Salmonella enterica is pathogen of importance to public health. Among factors that contribute to the survival of S. enterica in the food production chain and its prevalence as etiological agent in outbreaks, antimicrobial resistance (AMR), virulence and the ability to adapt to stresses stand out. The Mentha piperita L. essential oil (MPEO) has been suggested as antimicrobial to control S. enterica during food processing. The advantage described for the use of this substance in foods is mixture of compounds with different mechanisms of action, it that would be difficult inducing AMR and adapting to pathogens. The present study investigated AMR determinants, virulence factors and stress response genes in 37 isolates of S. enterica of food and patients of outbreak in Brazil over seven years using whole genome sequence (WGS) and phylogenetic analyzes. Subsequently, S. Typhimurium (CFSAN077727), selected for its genomic characteristics, was exposed successively to the MPEO to assess the effects on culturability and physiological functions using flow cytometry (FC) analyzes. Genomic analyzes revealed disagreement with conventional serotyping in 19 (51%) isolates, with isolates redistributed in 10 serovars. Analysis of AMR revealed the presence of genes for resistance to aminoglycosides [aac (6 ') - laa, aph (3' ') - lb, aph (6) -ld, aadA1 and aadA2], sulfonamides (sul1), trimethoprim (dfrA8), fosfomycin (fosA7) and tetracyclines (tetA, tetB, tetC), well as mutations in parC (T57S) and gyrA (S83F) in the genome of the isolates. Plasmids IncHI2, IncHI2A, IncFIB (S), IncFII (S), IncI1 and p0111 were identified, eight Salmonella pathogenicity islands (SPIs) and up to 102 stress and/or virulence genes in the studied genomes. The virulence genes of fimbrial adhesin K88 were first reported in S. Pomona, S. Bredeney and S. Mbandaka. The pilW gene was first identified in S. Pomona. Phylogenetic analysis showed that some serovars have been circulating in Brazil for decades, mainly in the poultry production chain. Successive exposure of S. Typhimurium to the same MPEO concentration (1.25 μL/mL) reduced the population with damaged, permeabilized and depolarized membrane and with efflux activity compromised over 252 h of exposure to MPEO. When S. Typhimurium was exposed to increasing concentrations of MPEO (1.25–80 μL/mL) there was an increase in damage to the same physiological functions. Phylogenetic analyzes of S. Typhimurium showed its persistence for more than 16 years in poultry sources. The results expand current knowledge about the persistence of S. enterica strains in the food production chain, evidencing factors of AMR, stress and virulence in interface that can lead to recurrent outbreaks. Furthermore, the data reveal that successive exposure to sublethal concentration of MPEO induces repair functions in S. Typhimurium, despite its non-cultivable state. These data reinforce the persistence of S. enterica in the food production chain and alert to the need for further studies microbial responses to MPEO.