Title: Tackling the true prevalence and levels of listeria monocytogenes: market basket surveys of ready-to-eat retail foods Author
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 13, 2011
Publication Date: June 16, 2011
Citation: Luchansky, J.B. 2011. Tackling the true prevalence and levels of listeria monocytogenes: market basket surveys of ready-to-eat retail foods. Joint Institute for Food Safety and Applied Nutrition (JIFSAN) and Food and Environment (FERA), Greenbelt, Maryland, June 15-17, 2011, Volume 1, Page 1. Technical Abstract: Listeria monocytogenes remains a serious threat to public health due to its prevalence, persistence, and pathogenicity in our food supply, particularly when associated with ready-to-eat (RTE) foods. For the past decade or so, considerable resources have been directed to reduce human illness attributable to RTE foods, yet despite these efforts, food borne listeriosis still occurs. The Food and Drug Administration (FDA) and Food Safety and Inspection Service (FSIS) developed a quantitative risk assessment in 2001 and used it to subsequently compare the relative risk of listeriosis among 23 categories of RTE foods in 2003. A study in 2006 (Draughon et al., 2006) provided additional insight into the prevalence and levels of this pathogen on deli-sliced versus prepackaged deli meats, and showed a greater prevalence on the former than on the latter. In fact, more recent risk assessments have also revealed that appreciably more illness/death due to listeriosis from deli meats can be attributed to retail sliced rather than prepackaged products. To minimize the load and occurrence of the pathogen and concomitantly continue efforts to develop and implement effective interventions to ensure that an infectious dose of L. monocytogenes will not reach the consumer’s table, it is imperative to quantify the prevalence, levels, and types of this pathogen in target foods. To this end, we conducted a multi-collaborator study to quantify the prevalence of L. monocytogenes in frankfurters, a higher-risk, high-volume and mass produced food, consumed by a significant segment of the population, including those at elevated risk (Wallace et al., 2003). The pathogen was recovered from 532 of 32,800 pounds/packages (1.6%) of frankfurters using the USDA Agricultural Research Service (ARS) package rinse method. Enumeration, when possible, showed pathogen levels of about 70 to 190 MPN (most probable number) per package; about 90% of the 1100 retained isolates were serotype 1/2a and displayed the same pulsotype. In a related study of similar scope and magnitude by Gombas et al. (2003), a total of 31,705 food samples (e.g., cheese, milk, raw fruits and vegetables, and deli salads) were tested, of which 577 samples tested positive for L. monocytogenes for an overall prevalence of 1.8%. Levels of the pathogen in positive samples ranged from <0.3 MPN per gram to 1.5 x 105 CFU (colony forming units) per gram. Since the data reported by Wallace et al. (2003) and Gombas et al. (2003) were collected some ten years ago, further studies were warranted to determine if the prevalence and populations of L. monocytogenes have increased, decreased, or remained static in response to the considerable efforts by food safety professionals across government, academia, and industry over the past decade to lower the likelihood of listeriosis associated with RTE foods. Thus, in collaboration with both FDA and FSIS, the ARS is conducting a Market Basket Survey to obtain more current information on the association of L. monocytogenes with RTE foods at retail to evaluate the relative public health risk. These baseline data will shed new light on the prevalence of this pathogen and prove useful to risk assessors and regulators worldwide because of the design and scope of the study wherein these data are being generated.