P3-39 Pulsed-field Gel Electrophoresis Subtyping of Salmonella Isolates from Carcasses, Lymph Nodes, and Fecal Samples from Cattle at Slaughter Facilities in Mexico

Wednesday, July 31, 2013
Exhibit Hall (Charlotte Convention Center)
Diana Ayala, Texas Tech University, Lubbock, TX
Mindy M. Brashears, Texas Tech University, Lubbock, TX
Kendra Nightingale, Texas Tech University, Lubbock, TX
Mark Miller, Texas Tech University, Lubbock, TX
Claudia Narvaez Bravo, Texas Tech University, Lubbock, TX
J. Chance Brooks, Texas Tech University, Lubbock, TX
Alex Brandt, Texas Tech University, Lubbock, TX
Introduction:  Salmonella is one of the leading causes of foodborne illnesses worldwide; in Mexico and other developing countries limited information on the prevalence of this pathogen at pre-harvest exists. Pulsed-Field Gel Electrophoresis (PFGE) is considered the "gold standard" Salmonella subtyping method due to its discriminatory power to differentiate among isolates, and its ability to determine relationships between PFGE patterns and particular serotypes.

Purpose:  This study aimed to 1) analyze the relationship between Salmonella serotypes and PFGE patterns from beef carcasses and feedlot isolates and 2) to molecularly characterize Salmonella isolates from lymph nodes and fecal samples of cattle from slaughter facilities in Mexico

Methods:  A set of 93 Salmonella isolates from beef carcasses and feedlot, previously serotyped, were used to perform PFGE. In addition, 33 Salmonella isolates from lymph nodes (mandibular, mediastinal, and mesenteric) and feces from 12 animals were analyzed to assess genetic relatedness. Subtyping was performed according to the PulseNet PFGE protocol for Salmonella serotypes.

Results:  The serotypes previously identified were S. Muenster (26.9%), S. Kentucky (19.4%), S. Reading (15.1%), S. Anatum (12.9%), S. Give (5.4%), S. Mbandaka (5.4%), S. Montevideo (3.2%), and S. Tennessee (2.0%). Nine samples (9.7%) were not identified by traditional serotyping, 77.7% of them were associated to a PFGE subtype when analyzed by PFGE. Salmonella Kentucky was  the most clonal in this study, 100% of the isolates had indistinguishable PFGE pattern; S. Muenster was the most diverse, 11 different subtypes were identified. Cluster analysis of PFGE patterns showed great relation (90.3%) between serotypes and PFGE subtypes.

Significance:  Results suggest there is a high concordance between serotypes and PFGE subtypes among isolates from beef carcasses and feedlot from Mexico. The diversity observed inter and intra-serotypes is important to discriminate among clones to enhance epidemiological studies. More research is needed to improve interventions at different points in the food chain.