October 25, 2018
CDC, public health and regulatory officials in several states, and the U.S. Food and Drug Administration (FDA)External investigated a multistate outbreak of Salmonella Enteritidis infections.
Public health investigators used the PulseNet system to identify illnesses that were part of this outbreak. PulseNet is the national subtyping network of public health and food regulatory agency laboratories coordinated by CDC. DNA fingerprinting was performed on Salmonella bacteria isolated from ill people by using techniques called pulsed-field gel electrophoresis (PFGE) and whole genome sequencing (WGS). CDC PulseNet manages a national database of these DNA fingerprints to identify possible outbreaks. WGS gives a more detailed DNA fingerprint than PFGE. WGS performed on bacteria isolated from ill people showed that they were closely related genetically. This means that people in this outbreak were more likely to share a common source of infection.
As of October 24, 2018, 44 people infected with the outbreak strain of Salmonella Enteritidis were reported from 11 states. A list of the states and the number of cases in each can be found on the Map of Reported Cases page.
Illnesses started on dates ranging from May 17, 2018 to August 26, 2018. Ill people ranged in age from one year to 94, with a median age of 32. Sixty percent of ill people were female. Of 37 people with information available, 12 (32%) were hospitalized. No deaths were reported.
WGS analysis did not predict antibiotic resistance in bacteria isolated from 25 ill people and 1 food sample. Testing of three clinical isolates using standard antibiotic susceptibility testing methods by CDC’s National Antimicrobial Resistance Monitoring System (NARMS) laboratory also did not show antibiotic resistance.
Investigation of the Outbreak
Epidemiologic, traceback, and laboratory evidence indicated that shell eggs from Gravel Ridge Farms were the likely source of this outbreak.
State and local health officials interviewed ill people and asked questions about the foods they ate and other exposures in the week before they became ill. Twenty-six (81%) of 32 people interviewed reported eating restaurant dishes made with eggs. This percentage was significantly higher than results from a survey Cdc-pdf[PDF – 787 KB] of healthy people in which 38% of respondents reported eating any eggs away from home in the week before they were interviewed. These restaurants reported using shell eggs in the dishes eaten by ill people.
FDA and state partners traced the source of the shell eggs supplied to these restaurants. Gravel Ridge Farms in Cullman, Alabama, supplied shell eggs to restaurants where 20 of the 26 ill people ate eggs. Several ill people lived in states where Gravel Ridge Farms shell eggs were not sold, but most traveled to states where they were sold in the week before their illness began.
The outbreak strain of Salmonella Enteritidis was identified in environmental samples from Gravel Ridge Farms. Officials in Alabama also collected eggs from the Gravel Ridge Farms facility for testing. The outbreak strain of Salmonella Enteritidis was identified in these eggs. WGS results showed that the Salmonella bacteria from the environmental samples and from Gravel Ridge Farms eggs were closely related genetically to the Salmonella bacteria isolated from ill people. These results provided more evidence that people in this outbreak got sick from eating shell eggs from Gravel Ridge Farms.
On September 8, 2018, Gravel Ridge Farms recalledExternal cage-free large eggs with use by dates of July 25, 2018 through October 3, 2018 because they might have been contaminated with Salmonella bacteria.
This outbreak appears to be over.