Antimicrobial resistance and genotypic profiles of Salmonella Saintpaul isolated along beef processing and distribution continuum

Salmonella Saintpaul (SSa) is increasingly reported from food and foodborne outbreak cases. Pulsed field gel electrophoresis (PFGE) is used for screening and tracking of Salmonella infections. Widespread use of antimicrobial agents in humans and food animals could result in antimicrobial resistant Salmonella serotypes. The aim of this study was to characterize S. Saintpaul (n = 28) isolated from various sampling locations at abattoir and meat processing plant lines in Ethiopia for phenotypic antimicrobial resistance and genotypic diversity, and to track its transfer routes. Sampling location, steps and occasions were considered for each isolate description. Antimicrobial sensitivity testing was performed against seven different antimicrobial agents using disc diffusion method. PFGE with XbaI(®) enzymatic genomic digestion with BioNumerics(®) analysis was used for genotypic diversity. Of all the isolates tested, only 17.9% were pan susceptible, and 82.1% were resistant to at least one and at most to three antimicrobials. All isolates were susceptible to gentamycin, trimethoprim-sulfamethoxazol and trimethoprim. Resistance to oxytetracycline (82.2%) was predominant followed by 3.6% resistance to each of chloramphenicol, neomycin and polymyxin B. PFGE analysis revealed three distinguishable clusters of pulsotypes but the majority of the isolates (25/28) belonged to cluster-I (SSaX1-4) pulsotype. Indistinguishable/similar cluster of (SSaX 1-4) isolates among and between sampling location, steps and occasions were observed. Majorities of S. Saintpaul (88%) in the cluster-I pulsotype were resistant to oxytetracycline. Our study indicated that oxytetracycline resistance is very common among the S. Saintpaul isolates studied; and the isolates were diverse with similar resistance profiles within the same genomic pulsotypes. Transfer of S. Saintpaul within, between and across sampling locations, during the same or different occasion were determined from SSaX 1-4 pulsotype while cluster-II (SSaX5) indicates transfer from abattoir to butchery. The unique isolate in cluster-III (SSaX6) shows the presence of other possible source of S. Saintpaul for the beef chain contamination.