Salmonella clinical isolates from Brazilian pig herds: genetic relationship and antibiotic resistance profiling

Abstract In Brazil, since 2011 clinical cases of salmonellosis has been increasing substantially. Nevertheless, few information is available about the antimicrobial profile, distribution, serotypes and genetic relationship among the strains. The objectives of this study were: to identify the Salmonella serotypes, to characterize the in vitro antimicrobial resistance profiles and to determine the genetic relationship of clinical isolates in Brazil. During 2016, clinical isolates of Salmonella (111) from nine States were sent to Embrapa Swine and Poultry for complementary analysis. First, isolates were serotyped by Kauffmann White Scheme. In parallel, the strains were tested against fifteen antimicrobials by disk diffusion method and genotyping was performed by Pulsed Field Gel Electrophoresis (PFGE) using the XbaI restriction enzyme. As expected, the main serovars found were Typhimurium and Choleraesuis. Four strains showed resistance to only one antimicrobial and 76.5% (85/111) were considered multiresistant. The highest level of resistance was found against to tetracycline. More than 80% of the strains were susceptible to fosfomycin, lincomycin/spectinomycin and norfloxacin. It was possible to identify one major Choleraesuis clonal group present in different Brazilian States. Further, several small clonal groups were obtained for Typhimurium. In conclusion, clinical salmonellosis caused by Typhimurium and Choleraesuis is endemic in pig production areas and the majority of the strains are multi-resistant