PROBABILISTIC MODEL AND GENETIC CHARACTERISTICS OF SALMONELLA IN BROILER PRODUCTION

Abstract

The objectives of this study were to apply probabilistic models to describe the dynamics of Salmonella contamination in an integrated broiler production and to investigate genetic characteristics and antibiotic resistance patterns of Salmonella isolated throughout the broiler production. The samples were chronologically collected in an integrated broiler production located in the Northeastern Thailand during 2010-2012. A total of 1,449 chicken-related samples and 935 environmental samples from three broiler production cycles were collected in a series of production units i.e., “breeding farm”, “hatchery”, “broiler farm” and “slaughterhouse”. The Salmonella isolates were tested for their genetic characteristics and antimicrobial resistance patterns by using pulsed-field gel electrophoresis (PFGE) and disk diffusion method, respectively. For the probabilistic models, beta and lognormal distributions were used to describe the uncertainty of contamination in terms of prevalence and concentration, respectively. The probability of Salmonella contamination in various sample types as well as in different production units were used as input variables of the probabilistic model. From PFGE pattern analysis, identical PFGE patterns of Salmonella isolates between chicken-related and environmental samples were found in all production units. This finding indicated Salmonella transfer between the chicken and its environment. This study suggested that contaminated equipment and environment in the hatchery, contaminated day-old chick, feed, water and pest especially house lizard were among the importance sources of Salmonella during the broiler production. In addition, the cross contamination during the slaughter process was the main element for Salmonella dissemination to the chicken carcasses. The sensitivity analysis indicated that the highly significant sources of contamination during rearing in the broiler farm were day-old chicks and pest. The most significant units contributing to the broiler carcasses contamination were pre-slaughter and slaughterhouse. The alarming rates of multidrug-resistant Salmonella were found among the isolates collected from the breeding farm (92.9%), hatchery (71.4%), broiler farm (36.6%), and slaughterhouse (78.0%). This result emphasized the importance of prudent use of antimicrobial agents and related chemicals in the broiler production. In conclusion, this study provided both qualitative and quantitative information on dynamics of Salmonella contamination and important sources of the contamination in broiler production. This scientific evidence is essential for risk assessors and risk managers in both government and private sectors to readily implement the holistic and realistic Salmonella control measures.