The FDA says the outbreak of Salmonella Newport infections linked to three farms in Indiana is over, but the agency has not named the farms.
The melon farms were also linked to at least four previous outbreaks, including one in 2022. Both cantaloupe and watermelon are implicated in this year’s outbreak. The FDA did not name the farms linked to the previous outbreaks, but a report on the 2022 outbreak referenced Knox and Gibson Counties of Indiana. In the 2022 outbreak, 87 people were sickened, and 32 were admitted to hospitals.
In this year’s investigation, there were three environmental samples collected from farms in the Southwest Indiana growing region that matched the strain of Salmonella Newport that caused illnesses in the 2023 outbreak. The samples that were reported as a match to previous outbreaks were collected from one farm of interest and surrounding areas.
“This year’s findings indicate continued presence of food safety concerns linked to melons from the Southwest Indiana growing region,” according to the Oct. 12 outbreak notice from the Food and Drug Administration.
The FDA has closed its investigation into the outbreak.
The Centers for Disease Control and Prevention assisted the FDA in the outbreak investigation and found that all 11 confirmed outbreak patients ate watermelon and cantaloupe before becoming sick. The patients were clustered in the Midwest, according to the CDC.
Some likely, many more patients went unidentified because some people do not seek medical attention, and some who do are not explicitly tested to diagnose Salmonella infection. Generally, there are about 30 patients for every one confirmed case of Salmonella infection, according to CDC data.
“Currently, there is no risk to the public, as all product (from the specific growing region) is no longer on the market,” the FDA notice says.
The FDA collected samples for analysis during its investigation. Salmonella in the samples from the Indiana farms matched the strain of the pathogen found in the confirmed outbreak patients.
“Additionally, samples collected from a farm of interest and surrounding areas were reported as positive for Salmonella and matched strains that have caused previous outbreaks, including those discussed in the 2022 Outbreak Investigation Report,” the FDA reported.
Highlights from the 2022 report
The 15-page 2022 investigation report says several turkey feeding operations were observed in the immediate area of the melon growing fields; the nearest is located within one mile of a field on “Farm 1.” A drainage ditch was adjacent to the field, which could have sent flood waters onto the field.
“Isolates collected from Farm 1 were classified into an NCBI S. Typhimurium grouping. These isolates represent a single strain that matches three human clinical cases collected between 2016 – 2018, indicating that this strain has caused disease. The isolates recovered from Farm 1 were genetically related to the 2022 multistate Salmonella Typhimurium outbreak, as well as isolates sampled from cantaloupe in 2013, isolates collected from Indiana ground turkey in 2016, and isolates from a 2020 Indiana soil subsample,” according to the FDA report.
Investigators collected soil samples from the growing field and found Salmonella Typhimurium isolates. Whole genome sequencing analysis found that these isolates represent a single strain that matches human clinical isolates from 2016, 2017, and 2018, indicating that the strain has caused illnesses, according to the FDA’s report.
At “Farm 2,” investigators found 30 Salmonella Newport isolates in soil samples.
“. . . The 30 isolates represent two separate strains. Isolates from two-thirds of Salmonella-positive drag swabs matched Salmonella Newport isolates recovered from Farm 3, isolates recovered from the post-harvest handling and packing entity associated with this outbreak, and 23 human clinical isolates collected between 2017 – 2022, indicating that this strain has caused illnesses. Isolates derived from the third drag swab were a match to 3 human illness clinical isolates recovered in 2016, 2019, and 2021, indicating that this strain has also caused illnesses,” according to the FDA’s report.
At “Farm 3” a turkey feeding operation is within a 2-mile radius of the cantaloupe field. Heavy rains that could have led to runoff from the turkey operation into the growing area were noted during the growth or harvest of the crop by investigators. The Farm 3 representative indicated that these extreme weather events did not negatively affect the growth or management of the cantaloupe crop.
“ (A soil sample) resulted in the collection of five Salmonella Newport isolates which were determined by WGS (whole genome sequencing) analysis to represent a single strain,” according to the FDA report on Farm 3. “These isolates were a match to Salmonella Newport isolates recovered from Farm 2, isolates recovered from the post-harvest handling and packing entity associated with this outbreak, along with 23 human clinical isolates collected between 2017 – 2022, indicating that this strain has caused illnesses.”
A sample from Farm 3’s packing house, which consisted of 55 environmental sponge swabs collected from equipment dedicated to packing cantaloupes, resulted in a positive test for Salmonella Newport. Whole genome sequencing revealed that these isolates matched isolates recovered from Farms 2 and 3, along with 23 human clinical isolates collected between 2017 – 2022, indicating that this strain has caused illnesses.
“Considering these findings, the FDA is continuing an ongoing assessment of this region to better understand the presence of pathogens in the growing environment,” according to the FDA’s report on the 2022 outbreak.
“. . . The recovery of multiple and diverse strains of Salmonella within the immediate growing and non-growing environments suggests that the region may contain multiple reservoirs for Salmonella spp.”
The FDA recommended the operators of the three implicated farms use improved traceability methods by implementing increased digitization, interoperability, and standardization of traceability records, which would expedite traceback and help remove contaminated products from the marketplace more quickly, thereby preventing further illnesses.
“This is not only important for growers, but also critical for shippers, manufacturers, and retailers to improve overall traceability throughout the supply chain,” the FDA report said.
(To sign up for a free subscription to Food Safety News, click here.)