Antimicrobial-Resistant Salmonella Heidelberg Outbreak Associated with Mechanically Separated Chicken in a Correctional Facility, Tennessee, 2013

BACKGROUND: Salmonella Heidelberg has been isolated from poultry products in local and multi-state outbreaks and has been shown to cause increased rates of hospitalization. Since 1998, Tennessee has reported 8 Salmonella Heidelberg foodborne outbreaks resulting in a total of 140 illnesses and 17 hospitalizations.  We investigated an outbreak of antimicrobial-resistant SalmonellaHeidelberg associated with mechanically separated chicken (MSC) at a correctional facility.

METHODS: Surveillance and investigation were initiated by the regional health department. Inmates and officers reporting illness were interviewed about symptoms, activities, and foods eaten during the previous week. A case was defined as an inmate or officer reporting diarrhea (≥3 loose stools in a 24-hour period) since November 27, 2013. A case-control study was conducted among inmates.  An environmental health assessment was performed and samples of suspected foods, including chubs of MSC, were collected. Bacterial isolates from case-patients and food were molecularly subtyped using pulsed-field gel electrophoresis (PFGE). Antimicrobial susceptibility testing was performed on food and human isolates. Traceback was conducted by the Tennessee Department of Health and the USDA-FSIS.

RESULTS: We identified 29 cases, of which 24 (84%) were inmates. Inmates reported illness onsets from November 28 to December 3. Officers reported illness onsets from December 2 to December 5. Three (10%) inmates were hospitalized.  Twenty-one (72%) cases reported fever and seventeen (59%) reported vomiting.  At the time of the interview, 14 (45%) of 29 cases had recovered and duration of diarrhea was a median of 4.5 days (range 1-8 days). The case-control study included 16 cases and 16 controls. No food item was significantly associated with illness. Stool specimens were collected from 13 inmates; 9 (69%) were positive for Salmonella Heidelberg with indistinguishable PFGE patterns. Testing of an unopened MSC chub received at the jail on November 22 yielded Salmonella Heidelberg indistinguishable from the outbreak subtype. Two isolates from cases-patients were resistant to third generation cephalosporins. The environmental health assessment identified the possibility of cross-contamination through improper hand washing, poor personnel hygiene, and inadequate sanitation of utensils. The MSC manufacturer initiated a voluntary recall.

CONCLUSIONS: Contaminated MSC and poor food handling practices contributed to a substantial Salmonella Heidelberg outbreak. Antimicrobial-resistant Salmonella may have contributed to more severe illness. Foodhandlers in institutional settings should receive food safety training to minimize the risk of illness associated with high-risk foods such as MSC.