Buffered peptone water formulation does not influence growth of pESI-positive Salmonella serovar Infantis

Authors: McMillan, Elizabeth; Berrang, Mark; Read, Quentin; RAMASETTI, SURENDRA - University Of Georgia; RICHARDS, AMBER - University Of Georgia; SHARLAT, NIKKI - University Of Georgia; Frye, Jonathan

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2022
Publication Date: 12/23/2022
Citation: Mcmillan, E.A., Berrang, M.E., Read, Q.D., Ramasetti, S., Richards, A.K., Sharlat, N.W., Frye, J.G. 2022. Buffered peptone water formulation does not influence growth of pESI-positive Salmonella serovar Infantis. Journal of Food Protection. https://doi.org/10.1016/j.jfp.2022.100033.
DOI: https://doi.org/10.1016/j.jfp.2022.100033

Interpretive Summary: Salmonella is an important human bacterial pathogen that causes many foodborne outbreaks. Salmonella has long been specifically associated with poultry and poultry meat food products. There are more than 2,500 serotypes of Salmonella; over the years different serotypes have been prevalent in poultry and human disease outbreaks. Until recently, Salmonella serotype Infantis has been detected relatively infrequently in poultry. However, starting in 2016, S. Infantis has been detected more frequently in chicken and turkey meat. Upon closer examination it was discovered that most of the S. Infantis being detected included a genetic marker in the form of a novel DNA plasmid which has been named pESI. Interestingly, at the same time that S. Infantis detection increased, the method used by USDA to determine the Salmonella status of poultry meat changed to include a new Salmonella detection broth. The new broth, called nBPW, was designed to counteract residual antimicrobial processing chemicals and allow more accurate detection of Salmonella. The co-incident nature of the increase in detection of S. Infantis and employment of a new broth for detection led some to speculate that nBPW may actually be somehow promoting the growth and detection of S. Infantis more than the original broth (BPW). We compared survival during overnight cold shipment and growth during incubation of 10 S. Infantis poultry isolates in BPW and nBPW. We found no difference according to which broth was used. It appears from our data that the change in regulatory methodology did not cause the increase in S. Infantis detection from poultry meat. It remains to be determined what has caused the increase in S. Infantis in poultry. More research is being planned to determine why we are finding more of this serotype and what can be done to continue to improve poultry production and processing to assure a safe and wholesome product is delivered to consumers.

Technical Abstract: Salmonella enterica is a major cause of human foodborne illness and is often attributed to poultry food sources. Salmonella serovar Infantis, especially those carrying the pESI plasmid, has become a frequently isolated serotype from poultry meat samples at processing and has caused numerous recent human infections. In 2016, the Food Safety and Inspection Service changed the official sampling method for raw poultry products to using nBPW as the rinsing agent. This change was contemporaneous to the emergence of pESI-positive S. Infantis as a prevalent strain in poultry, prompting some to question if neutralizing buffered peptone water (nBPW) could be selecting for this prevalent strain. We performed two experiments: a comparison of S. Infantis growth in BPW versus nBPW, and a simulation of regulatory sampling methods. We found that when inoculated into both broths, S. Infantis initially grows slightly slower in nBPW than in BPW but little difference was seen in abundance after six hours of growth. Additionally, use of nBPW to simulate poultry rinse sample and overnight cold shipping to a regulatory lab did not affect survival or subsequent growth of S. Infantis in BPW. We concluded that the change in USDA-FSIS methodology to include nBPW in sampling procedures has likely not affected the emergence of S. Infantis as a prevalent serovar in chicken and turkey meat product samples.