Multi-State Outbreak of Drug-Resistant Salmonella

The CDC is collaborating with public health and agriculture officials in many states and the U.S. Department of Agriculture's Food Safety and Inspection Service (USDA-FSIS) to investigate a multistate outbreak of Salmonella Heidelberg infections. Seven strains of Salmonella Heidelberg bacteria have been identified as being linked to this outbreak. Four of these strains are rarely reported. The other three strains are more common, with several ill persons infected with each strain reported to the CDC monthly. The DNA fingerprints of the Salmonella Heidelberg bacteria associated with the current outbreak include the strain that was also associated with a multistate outbreak of Salmonella Heidelberg linked to Foster Farms brand chicken during 2012-2013.


Preliminary laboratory testing identified four of the seven outbreak strains from multiple chicken product samples at three Foster Farms facilities. The products were mainly distributed to retail outlets in California, Oregon and Washington State. Raw products from the facilities in question bear one of the establishment numbers inside a USDA mark of inspection or elsewhere on the package "P6137," "P6137A," and "P7632."


Most persons infected with Salmonella bacteria develop diarrhea, fever, and abdominal cramps 12 to 72 hours after infection. The illness usually lasts 4 to 7 days, and most persons recover without treatment. However, in some persons, the diarrhea may be so severe that the patient needs to be hospitalized. Salmonella infection may spread from the intestines to the bloodstream and then to other body sites and can cause death unless the person is treated promptly with antibiotics. Children younger than 5 years, older adults, and people with weakened immune systems are more likely to have a severe illness from Salmonella infection. While it is not unusual for raw poultry from any producer to have Salmonella bacteria, it is uncommon for poultry to have multidrug-resistant Salmonella bacteria.


As of October 11, 2013, a total of 317 individuals infected with the outbreak strains of Salmonella Heidelberg have been reported from 20 states and Puerto Rico. Most of the ill persons (73%) have been reported from California. Since the last update on October 8, 2013, a total of 39 additional ill persons have been identified from 9 states and Puerto Rico: Arizona (2), California (19), Florida (2), Kentucky (1), Missouri (5), Nevada (1), New Mexico (2), Puerto Rico (1), Texas (4), and Virginia (2). Of the 39 additional ill persons, two have estimated illness onset dates after September 24, 2013, the last illness onset date reported in the October 8, 2013 outbreak announcement.


Among the 310 persons for whom information is available, illness onset dates range from March 1, 2013, to September 26, 2013. Ill persons range in age from less than 1 year to 93 years, with a median age of 20 years. Fifty-one percent of ill persons are male. Among 189 persons with available information, 79 (42%) reported being hospitalized. Thirteen percent of ill persons developed blood infections as a result of their illness. Typically, approximately 5% of persons ill with Salmonella infections develop blood infections. No deaths have been reported.


Illnesses that occurred after September 5, 2013 might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of 2 to 3 weeks.


To date, seven strains of Salmonella Heidelberg have been included in this investigation based on epidemiologic, laboratory and traceback information. The information collected for cases associated with each strain indicates that each of the strains is linked to this outbreak of multidrug-resistant Salmonella Heidelberg infections and that Foster Farms brand chicken is the likely source.


The CDC's National Antimicrobial Resistance Monitoring System for Enteric Bacteria (NARMS) laboratory conducted antibiotic-resistance testing on clinical isolates collected from ten ill persons infected with three of the seven outbreak strains. Nine of these isolates exhibited drug resistance to one or more commonly prescribed antibiotics. Of those, three were multidrug resistant. One isolate was susceptible to all antibiotics tested. To date, isolates collected from ill persons were resistant to combinations of the following antibiotics: ampicillin, chloramphenicol, gentamicin, kanamycin, streptomycin, sulfisoxazole, and tetracycline. Antimicrobial resistance may increase the risk of hospitalization or possible treatment failure in infected individuals.


On October 10, 2013, the USDA-FSIS announced that Foster Farms submitted and implemented immediate substantive changes to their slaughter and processing to allow for continued operations. FSIS inspectors will verify that these changes are being implemented on a continuous and ongoing basis. Additionally, the agency will continue intensified sampling and testing of chicken products from these facilities for at least the next 90 days.


See the CDC Investigation Report


See the CDC Signs and Symptoms Report


See also Medical Risk Law, July 2012 Report: Foodborne Illness: When Grabbing a Bite Can Be Deadly