Sequential Transmission of Salmonella in the Slaughtering Process of Chicken in Korea

Salmonella is one of the most common foodborne pathogens worldwide. Salmonella infections in humans are mainly associated with consumption of poultry products contaminated with this foodborne pathogen. Therefore, strict sanitary measures are necessary to control Salmonella contamination during the slaughtering process of poultry. The objective of this study was to determine the occurrence and transmission of Salmonella at a series of steps in the slaughtering process of chicken. A total of 601 samples were collected from a series of slaughtering steps (10 sampling sites) of 26 chicken slaughterhouses throughout Korea. Salmonella was isolated from samples and its distribution was analyzed along the slaughtering process. Isolates from each sampling site were tested for susceptibility to 15 antibiotics by the broth microdilution method. They were also genotypically characterized by pulsed-field gel electrophoresis (PFGE). Salmonela was isolated from 168 out of 601 samples. Sixteen serotypes were identified while six isolates were untypable. Salmonella enterica serovars Montevideo (n = 29) and Virchow (n = 27) were the most common serotypes out of 119 nonredundant isolates. Relatively high contamination rates of Salmonella were found in shackles (75.0%), feathers near plucking machine (68.5%), and feces from crates (44.0%). Twenty-three antibiotic resistance patterns were recognized and 40 (33.6%) isolates were resistant to five or more antibiotics. The same serotypes of Salmonella were distributed along the slaughtering process of each Salmonella-positive slaughterhouse. Most of those isolates belonging to the same serotype had identical or closely related PFGE profiles. They also shared common antibiotic resistance patterns. Overall findings of this study indicated that Salmonella were sequentially transmitted through the chicken slaughtering process. PRACTICAL APPLICATION: This study provides useful information on the distribution and transmission of Salmonella serotypes through the chicken slaughtering process. Overall findings indicated the need for routine microbiological monitoring along the slaughtering process. This study also showed that on-farm control of Salmonella is needed to obtain Salmonella-free chicken carcasses.