Application of Bayesian Techniques to Model the Burden of Human Salmonellosis Attributable to U.S. Food Commodities at the Point of Processing: Adaptation of a Danish Model

Mathematical models that estimate the proportion of foodborne illnesses attributable to food commodities at specific points in the food chain may be useful to risk managers and policy makers to formulate public health goals, prioritize interventions, and document the effectiveness of mitigations aimed at reducing illness. Using human surveillance data on laboratory-confirmed Salmonella infections from the Centers for Disease Control and Prevention and Salmonella testing data from U.S. Department of Agriculture Food Safety and Inspection Service's regulatory programs, we developed a point-of-processing foodborne illness attribution model by adapting the Hald Salmonella Bayesian source attribution model. Key model outputs include estimates of the relative proportions of domestically acquired sporadic human Salmonella infections resulting from contamination of raw meat, poultry, and egg products processed in the United States from 1998 through 2003. The current model estimates the relative contribution of chicken (48%), ground beef (28%), turkey (17%), egg products (6%), intact beef (1%), and pork (<1%) across 109 Salmonella serotypes found in food commodities at point of processing. While interpretation of the attribution estimates is constrained by data inputs, the adapted model shows promise and may serve as a basis for a common approach to attribution of human salmonellosis and food safety decision-making in more than one country

National Outbreak of Multidrug Resistant Salmonella Heidelberg Infections Linked to a Single Poultry Company.

IMPORTANCE:This large outbreak of foodborne salmonellosis demonstrated the complexity of investigating outbreaks linked to poultry products. The outbreak also highlighted the importance of efforts to strengthen food safety policies related to Salmonella in chicken parts and has implications for future changes within the poultry industry. OBJECTIVE:To investigate a large multistate outbreak of multidrug resistant Salmonella Heidelberg infections. DESIGN:Epidemiologic and laboratory investigations of patients infected with the outbreak strains of Salmonella Heidelberg and traceback of possible food exposures. SETTING:United States. Outbreak period was March 1, 2013 through July 11, 2014. PATIENTS:A case was defined as illness in a person infected with a laboratory-confirmed Salmonella Heidelberg with 1 of 7 outbreak pulsed-field gel electrophoresis (PFGE) XbaI patterns with illness onset from March 1, 2013 through July 11, 2014. A total of 634 case-patients were identified through passive surveillance; 200/528 (38%) were hospitalized, none died. RESULTS:Interviews were conducted with 435 case-patients: 371 (85%) reported eating any chicken in the 7 days before becoming ill. Of 273 case-patients interviewed with a focused questionnaire, 201 (74%) reported eating chicken prepared at home. Among case-patients with available brand information, 152 (87%) of 175 patients reported consuming Company A brand chicken. Antimicrobial susceptibility testing was completed on 69 clinical isolates collected from case-patients; 67% were drug resistant, including 24 isolates (35%) that were multidrug resistant. The source of Company A brand chicken consumed by case-patients was traced back to 3 California production establishments from which 6 of 7 outbreak strains were isolated. CONCLUSIONS:Epidemiologic, laboratory, traceback, and environmental investigations conducted by local, state, and federal public health and regulatory officials indicated that consumption of Company A chicken was the cause of this outbreak. The outbreak involved multiple PFGE patterns, a variety of chicken products, and 3 production establishments, suggesting a reservoir for contamination upstream from the production establishments. Sources of bacteria and genes responsible for resistance, such as farms providing birds for slaughter or environmental reservoir on farms that raise chickens, might explain how multiple PFGE patterns were linked to chicken from 3 separate production establishments and many different poultry products

Persons Infected with the Outbreak Strains of <i>Salmonella</i> Heidelberg by State, n = 634, 2013–2014.

<p>Persons Infected with the Outbreak Strains of <i>Salmonella</i> Heidelberg by State, n = 634, 2013–2014.</p

Persons Infected with the Outbreak Strains of <i>Salmonella</i> Heidelberg, by Week of Illness Onset, March 2013-July 2014.

<p>Persons Infected with the Outbreak Strains of <i>Salmonella</i> Heidelberg, by Week of Illness Onset, March 2013-July 2014.</p

Case-patient Characteristics in Multistate Outbreak of Multidrug-Resistant <i>Salmonella</i> Heidelberg Infections Linked to a Single Poultry Company, by Pulsed-Field Gel Electrophoresis Pattern, 2013–2014.

<p>Case-patient Characteristics in Multistate Outbreak of Multidrug-Resistant <i>Salmonella</i> Heidelberg Infections Linked to a Single Poultry Company, by Pulsed-Field Gel Electrophoresis Pattern, 2013–2014.</p

Antimicrobial Susceptibility Testing Results, Multistate Outbreak of Multidrug-Resistant (MDR)^† <i>Salmonella</i> Heidelberg Infections Linked to a Single Poultry Company, 2013–2014.

<p>Antimicrobial Susceptibility Testing Results, Multistate Outbreak of Multidrug-Resistant (MDR)<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0162369#t003fn002" target="_blank">^†</a> <i>Salmonella</i> Heidelberg Infections Linked to a Single Poultry Company, 2013–2014.</p

Leftover Chicken Products Collected from Case-Patient Homes, Multistate Outbreak of Multidrug-Resistant <i>Salmonella</i> Heidelberg Infections Linked to a Single Poultry Company, 2013–2014.

<p>Leftover Chicken Products Collected from Case-Patient Homes, Multistate Outbreak of Multidrug-Resistant <i>Salmonella</i> Heidelberg Infections Linked to a Single Poultry Company, 2013–2014.</p