Salmonella in pigs slaughtered in Ecuador: prevalence, serotypes, genotypes and antibiotic resistance

Salmonella enterica subsp. enterica (S. enterica) is a leading foodborne pathogen worldwide, and pork products are major sources of infection. Given the lack of data on S. enterica infection in pigs slaughtered in Ecuador, this study aimed to determine its prevalence, as well as the serotypes, genotypes and antimicrobial susceptibility profiles of isolates from cecum contents (CCs) and mesenteric lymph nodes (MLNs) sampled from 365 pigs at the evisceration step at a slaughterhouse in Quito city. Salmonella spp. in the samples was detected by culture (ISO 6570-1 method). Strains were serotyped (ISO 6579-3 method), tested for antimicrobial susceptibility using the disk diffusion method, and genotyped by macrorestriction of chromosomal DNA. Salmonella enterica was detected in 56 of the 365 pigs sampled (15.3 %), in CCs (11.2 %) or MLNs (11.2 %) but never in both. The 56 isolates (one per positive sample) belonged to 12 serotypes, mainly the monophasic Salmonella Typhimurium (mST) (28.5 %) and S. Uganda (26.7 %). Twenty-two XbaI PFGE profiles were identified, with higher genetic diversity for S. Infantis and S. Uganda. A high percentage of isolates showed antimicrobial resistance to tetracycline (71.4 %) and streptomycin (62.5 %). Twelve antimicrobial multi-resistant patterns were observed, particularly associated with S. Typhimurium isolates, S. Infantis and mST. The present study constitutes the first investigation of S. enterica prevalence in a large-scale slaughterhouse in Ecuador. The findings will contribute to a better assessment of the epidemiology of S. enterica in the pork industry and of the associated public health risk.