Pulsed-field gel electrophoresis subtyping of salmonella isolates from carcasses, lymph nodes and fecal samples of cattle from slaughter facilities in Mexico

Salmonella is one of the leading causes of foodborne illnesses worldwide; however, in developing countries few surveillance programs exist, as a result limited information about the prevalence of this pathogen at pre-harvest is known. In order to identify the relationship between particular serotypes and PFGE patterns, 95 isolates from a Salmonella stock culture collection of the Food Microbiology Laboratory at Texas Tech University were analyzed; isolates were originally isolated from samples collected in Veracruz, Mexico in 2009. In addition, 33 confirmed Salmonella isolates from lymph nodes (mandibular, mediastinal, and mesenteric) and feces from cattle of one slaughter facility of Merida, Mexico were molecularly characterized by PFGE. High concordance (88.4%) was found between serotype and PFGE banding subtype; Salmonella Kentucky and Salmonella Give were found to be the most clonal in this study while Salmonella Muenster was the most diverse with 11 subtypes identified. For the second part of the study, six serotypes were identified, Salmonella Poona was found to be the most common and clonal identified. In addition, high diversity was observed among serotypes from lymph nodes and feces from the same animal. The diversity observed suggest multiple sources of contamination. The findings of this study reflect the need of improving interventions at different points in the food chain to avoid further Salmonella spread among carcasses.