Fate of Listeria monocytogenes and shiga toxin-producing Escherichia coli on bresaola slices during storage.

Authors: Porto-Fett, Anna; MCCOY, ASHLEY - University Of Nebraska; Shane, Laura; HENRY, ELIZABETH - Former ARS Employee; Osorio, Manuela; Shoyer, Brad; CAMPANO, STEPHEN - Hawkins, Inc; BURSON, DENNIS - University Of Nebraska; Luchansky, John

Submitted to: Meat and Muscle Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2022
Publication Date: 9/8/2022
Citation: Porto Fett, A.C., Mccoy, A., Shane, L.E., Henry, E., Osoria, M., Shoyer, B.A., Campano, S.G., Burson, D.R., Luchansky, J.B. 2022. Fate of Listeria monocytogenes and shiga toxin-producing Escherichia coli on bresaola slices during storage. Meat and Muscle Biology. 6(1). https://doi.org/10.22175/mmb.13918.
DOI: https://doi.org/10.22175/mmb.13918

Interpretive Summary: Bresaola (or brisaola) is a ready-to-eat (RTE), whole-muscle, salted, and aged (2 to 3 months) all-beef product that has been consumed for centuries without posing a serious public health risk. However, the association of pathogenic bacteria such as Shiga toxin-producing Escherichia coli (STEC) with raw beef and the likelihood for surface contamination with Listeria monocytogenes during slicing, assembling, and/or packaging of bresaola may be of concern, especially due to its extended shelf life. Thus, we monitored viability of cells of L. monocytogenes or STEC, surface inoculated onto slices of a single brand of a commercial all-beef bresaola, during refrigerated storage for 3 to 6 months to access the safety of this product. Our results demonstrated that slices of bresaola did not provide a favorable environment for outgrowth of these pathogens. In fact, pathogen levels decreased by ca. 100 cells per package during storage. Excluding the present study, few if any data have been published to quantify the fate of pathogens on commercial-prepared slices of bresaola during extended storage. As a RTE food, it remains possible for process deviations or post-process contamination of bresaola to occur which, in turn, may allow harmful bacteria to remain in contact with the finished product. Even if that were to occur, our data establish that bresaola would not support outgrowth or persistence of STEC or L. monocytogenes.

Technical Abstract: The viability of multi-strain cocktails of genetically marked strains of Listeria monocytogenes and Shiga toxin-producing Escherichia coli (STEC) were separately monitored on slices of one brand of a commercially-produced bresaola (ca. pH 6.4 and aw 0.872) during extended refrigerated storage. Two slices (ca. 8 g each; ca. 10.2 cm wide, ca. 11 cm long) of bresaola were layered horizontally within a nylon-polyethylene bag. The outer surface of each slice was inoculated (50 µL total; ca. 3.5 log CFU/package) with a rifampicin-resistant (100 g/ml) cocktail of either L. monocytogenes (five strains) or STEC (eight strains). Bags were vacuum-sealed and then stored at 4 or 10C for 180 or 90 days, respectively. In each of five trials, three bags were analyzed for pathogen presence at each sampling interval via the USDA-ARS package rinse method. In general, levels of L. monocytogenes and STEC decreased by 2.3 and 1.5 log CFU/package, respectively, after 180 days when bresaola was stored at 4C. When bresaola was stored at 10C for 90 days, levels of L. monocytogenes and STEC decreased by 2.0 and 1.7 log CFU/package, respectively. Thus, the (brand of) sliced bresaola evaluated herein did not provide a favorable environment for persistence or outgrowth of surface-inoculated cells of L. monocytogenes or STEC.