Purpose: FSIS developed an intensified sampling program to sample raw chicken products at six implicated establishments. Once three establishments were identified as the most likely producers of implicated products, FSIS monitored implementation of corrective actions and their effectiveness in reducing Salmonella at these establishments through continued intensified sampling.
Methods: FSIS applied a probability-based weighting scheme to choose establishments and product types most likely associated with this particular illness cluster for inclusion in the intensified sampling project. For over 12 months, FSIS analyzed samples for the presence of Salmonella, including routine subtyping analyses (e.g., serotyping, pulsed-field gel electrophoresis, and antimicrobial susceptibility testing). Product was collected in final retail packaging at these establishments and shipped to FSIS field service laboratories for subsequent analysis.
Results: During the initial phase of testing, the results showed approximately 25% Salmonella positive in chicken products at the implicated establishments. After corrective actions were implemented, FSIS testing in conjunction with establishment testing showed a reduction to at or below 5% Salmonella positive at the three implicated establishments.
Significance: This is the first time FSIS utilized a weighted approach for focusing intensified sampling resources as part of an outbreak investigation. Through this type of sampling, we were able to rule out establishments under the same corporate umbrella and focus on the three establishments where Salmonella appeared to be most elevated. As a result of corrective actions implemented in these establishments, the incidence of Salmonella was reduced, and over time the associated illnesses returned to background levels.