39% of ill people have been hospitalized but no deaths have been reported and most illnesses (74%) have been reported from California.
The outbreak strains are resistant to some commonly prescribed antibiotics, which may be associated with increased risk of hospitalization, said the US Centers for Disease Control and Prevention (CDC).
Four of these strains are rarely reported to PulseNet, the subtyping network that performs molecular surveillance of foodborne infections.
The investigation is ongoing and USDA-FSIS is prepared to take additional actions or expand the investigation based on new evidence, it said.
Of 34 isolates tested by CDC, 19 (56%) exhibited resistance to one or more antibiotics and seven (21%) of the 34 isolates were multidrug resistant.
Isolates collected from ill people were resistant to combinations of ampicillin, chloramphenicol, gentamicin, kanamycin, streptomycin, sulfisoxazole, and tetracycline.
The update said 416 people have been affected and 27 new cases were reported from four states: Arizona (2), California (22), Colorado (2), and Washington (1), since the 19 November update.
Foster Farms has been named as the likely source of the illnesses but there has been no recall as USDA-FSIS said products are safe to eat if they are properly handled and fully cooked to an internal temperature of 165°F.
USDA-FSIS issued a health alert on 7 October due to concerns with three Foster Farms facilities in California.
Three days later the agency announced the firm submitted and implemented substantive changes to their slaughter and processing to allow for continued operations.
However, on 12 and 17 October Costco’s El Camino Real store located in South San Francisco, California recalled more than 23,000 units of rotisserie chicken products due to possible Salmonella Heidelberg contamination.
The number of ill people by state are Alaska (1), Arkansas (1), Arizona (18), California (310), Colorado (9), Connecticut (1), Delaware (1), Florida (4), Idaho (4), Illinois (1), Kentucky (1), Louisiana (1), Michigan (3), Missouri (5), North Carolina (1), Nevada (10), New Mexico (2), Oregon (10), Puerto Rico (1), Texas (10), Utah (2), Virginia (3), Washington (16), and Wisconsin (1).
Ron Foster, president and CEO of Foster Farms, said the firm regrets any illness associated with their products in a statement made in October.
“We have worked relentlessly to address these issues and will continue to do so as we work to regain consumer trust and confidence in the Foster Farms brand.
“We are putting every resource and all of our energy toward food safety with the confidence that Foster Farms plants will be the most stringent in the industry.”