Submitted to: Journal of Food Protection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/22/2009
Publication Date: 9/1/2009
Citation: Musgrove, M.T., Mcquestin, O.J., Tamplin, M., Kelley, L.C. 2009. Growth and survival of antibiotic-resistant Salmonella Typhimurium DT104 in liquid egg products. Journal of Food Protection, 72:1992-1996. Interpretive Summary: Liquid egg products are transported in tankers that hold more than 55,000 gallons of product. Any liquid product is a potential biosecurity risk. Eggs are very nutritious for humans and bacteria. It had been unknown if Salmonella Typhimurium DT104 (ST DT104), a particularly virulent strain that is resistant to therapeutic antimicrobials would be a serious threat if inoculated into the whole liquid egg, albumen, yolk with 10% sugar, or yolk with 10% salt. This information was gained by inoculating each product type with ST DT104 and incubating at temperatures from 4 to 42oC. Numbers of ST DT104 were greatly increased in whole egg and yolk with 10% sugar but tended to decline in albumen and yolk with 10% salt. These results indicate that this strain grows no more rapidly than other serotypes or S. Typhimurium strains. Large volumes would need to be added and the product would have to remain at elevated temperatures for a long time for the numbers to increase to a level that would make them a danger to a large number of people, particularly since these products are consumed after cooking. This research will be used to generate risk models used by policy makers to more accurately assess potential threats.
Technical Abstract: Since September 11, 2001, quality and food safety are no longer the only concerns of consumers, industry, regulatory agencies, or other government officials. The US Department of Agriculture’s Food Safety Inspection Service is working with the Department of Homeland Security’s National Biodefense Analysis and Countermeasures Center (NBACC) and the interagency Technical Support Working Group (TSWG) on several studies pertaining to the use of certain threat agents in food. One of the foods considered to be at potential risk to sabotage was liquid eggs. Because of their versatility, low price, and many functional properties, there are many types of products being marketed. Four of the most common are whole egg, albumen, 10% sugared yolk and 10% salted yolk. While all of the serotypes of Salmonella enterica may cause illness, multidrug-resistant Salmonella Typhimurium DT104 has been shown to be both widespread and can cause severe illness that is difficult to treat. Studies were conducted to determine growth patterns of Salmonella Typhimurium DT104 in four commercial liquid egg products held at 4, 10, 20, 30, 37, and 42oC for 0 to 384 h. All experiments were performed in duplicate and repeated twice. Standard methods were used to estimate cellular numbers and log10 CFU/g egg product was plotted against time. The cellular density of S. Typhimurium DT104 increased to 8-9 log10 CFU/g in whole egg and 10% sugared yolk, increased by 1 log10 CFU/g in liquid albumen but decreased by 99.9% in 10% salted yolk. Data will be archived in the ComBase database to further assist policy makers in determining how best to respond to potential dangers. However, based on data generated in this study, it seems unlikely that Salmonella Typhimurium DT104 would constitute a food threat agent in liquid egg. Other egg-borne pathogens that produce heat stable toxins should be evaluated in these and other egg products.