Purpose: The objective of this study was to conduct a year-long market survey of Salmonella on raw poultry to help bridge the data gaps needs for use in a Quantitative Microbial Risk Assessment (QMRA). The main objectives include: determine the prevalence and concentrations of Salmonella species between various chicken parts and forms, and genetically characterize recovered Salmonella isolates.
Methods: A total of 1100 raw, fresh poultry carcasses from retail markets in Seattle, Washington, were included in the study. After an overnight incubation of 350 grams of samples at 42 ± 0.2°C in modified tryptic soy broth, a polymerase chain reaction (PCR) method was used to screen for Salmonella. The immunomagnetic separation procedure followed by a conventional culture-based method was used for the recovery of Salmonella. The most probable number method (MPN) and pulsed field gel electrophoresis (PFGE) were used for enumeration and to assess genetic relatedness of the isolates, respectively.
Results: Eight percent of the samples were positive for Salmonella. No seasonal variations in percent-positive rates and concentrations of Salmonella were observed. Percent-positive rates varied by processing establishments, processing types and sample forms. A significant portion of the positive samples had < 30 MPN/100 grams. There is an overlap in the genetic variability of Salmonella recovered from different establishments and by seasons.
Significance: A single prevalence rate of Salmonella on carcasses may not adequately describe the variability in risk. Therefore future QMRAs will need to consider the variability in the contamination rates of various chicken parts, forms and processing types.