Antimicrobial resistance in Salmonella spp. isolated from pig carcasses in two slaughterhouse types in Jalisco, Mexico

Salmonella is one of the main bacteria causing foodborne illness. Research into antimicrobial resistance in Salmonella is increasingly important as treatment of salmonellosis becomes more difficult. An analysis was done of samples from pig carcasses in two slaughterhouse types (federal-inspected and municipal) in the state of Jalisco, Mexico. Thirty-eight Salmonella strains were isolated, with fewer (P<0.05) strains (n= 1) in the federal-inspected slaughterhouse than in the municipal one (n= 37). This difference is probably due to stricter sanitation measures in the federal-inspected slaughterhouse. The main identified Salmonella serotypes were London (44.7 %), Anatum (15.8 %), and Agona, Muenchen and Typhimurium (7.9 %). Resistance was broadest against aminoglycosides (100 %), tetracyclines (73.7 %) and ciprofloxacin (44.7 %). Most (66.6 %) of the strains were resistant to three or four different antimicrobial classes. Presence of the gene coding for integrase 1 was confirmed. In the sampled slaughterhouses Salmonella strains have acquired genetic elements promoting resistance to different antimicrobial classes, potentially complicating treatment of infections caused by them. Implementation of better practices and compliance with existing regulations could contribute to reducing the frequency of Salmonella isolates in the sampled slaughterhouses.