Diversidade genética e determinantes de virulência e de resistência a antimicrobianos e sanitizantes em isolados de Salmonella spp. provenientes de carcaças bovinas e produtos cárneos

Abstract

Salmonella spp., bacterium that causes salmonellosis, is responsible for thousands of outbreaks of this Foodborne Disease each year worldwide. The treatment of severe cases of the infection can occur with the use of antimicrobials, to which Salmonella can acquire resistance, as well as they can become tolerant to sanitizers often applied in the food industry, making the bacteria a persistent source contamination in the production environment. The aim of manuscripts 1 and 2 of this study was to characterize 55 Salmonella spp. from beef and meat products from the city of Pelotas, regarding their phenotypic and genotypic profiles of virulence and resistance to antimicrobials and sanitizers, as well as to evaluate the genetic diversity among the isolates. All isolates presented at least one of the virulence genes evaluated in the study. Resistance to tetracycline and ampicillin were the most prevalent, and the phenotypic profile of multidrug resistance to antimicrobials was observed in more than half of the isolates (56.4%), of which 32.2% remained with serovar Typhimurium, and 96.8% of these multiresistant isolates were from meat products. Eleven antimicrobial resistance genes were detected in 31 Salmonella spp. isolates, among which the tet(A) and blaTEM genes were the most prevalent. Plasmids carrying antimicrobial resistance genes were found in 41.9% of the multiresistant isolates, with the tet(A) gene being the most detected in the plasmids. Tolerance to sanitizers was evaluated by the minimum inhibitory concentration, showing values of up to 128 μg.mL-1 for benzalkonium chloride and 32 μg.mL-1 for chlorhexidine, with the isolates being less tolerant to these compounds than to peracetic acid and sodium hypochlorite, which presented a minimum inhibitory concentration of 2048 μg.mL-1. Furthermore, nearly 90% of the isolates found to be benzalkonium chloride tolerant were isolated from meat products. The qacEΔ1 gene, which was the only sanitizer resistance gene detected in the isolates, is linked with the int1 gene, suggesting that there is a relationship between sanitizer tolerance and antimicrobial resistance in these isolates. Genetic diversity was observed among Salmonella isolates, especially in serovars Typhimurium, Anatum, Heidelberg and Derby. Clonality was observed only in serovar Senftenberg from bovine carcasses. The objective of manuscript 3 of this study was to investigate the occurrence and genetic diversity of Salmonella enterica subsp. enterica in sausages sold in southern Brazil, as well as to evaluate the presence of virulence genes and determine the phenotypic and genotypic profiles of resistance to antimicrobials and sanitizers. The prevalence of Salmonella in the analyzed sausage samples was 5.5%. The predominant serovars were S. Infantis and S. Rissen. Analysis by Pulsed Field Gel Electrophoresis (PFGE) revealed nine different profiles, and some of them were repeat offenders in the same establishment on different dates. A profile of multidrug resistance to antimicrobials was observed in 21.4% of the isolates, and the most frequent resistances were to ampicillin, sulfonamide, trimethoprim/sulfamethoxazole and trimethoprim. Only S. Schwarzengrund presented the tet(B), strA, strB and sul2 genes. Benzalkonium chloride and chlorhexidine were more effective than peracetic acid and sodium hypochlorite, with lower minimum inhibitory concentration values. The results observed in this study highlight the importance of good manufacturing practices in slaughterhouses and food processing environments, both in relation to cross-contamination and the misuse of sanitizing compounds, in order to reduce contamination with Salmonella that are multirresistant to antimicrobials and tolerant to sanitizers in meat and meat products. Also, six Salmonella serovars were found in sausages, demonstrating a potential risk of salmonellosis associated with the consumption of this food in southern Brazil.