Biofilm formation, antimicrobial resistance, and sanitizer tolerance of Salmonella enterica strains isolated from beef trim

Authors: Wang, Rong; Schmidt, John; Harhay, Dayna; Bosilevac, Joseph - Mick; King, David - Andy; Arthur, Terrance

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/2017
Publication Date: 12/1/2017
Citation: Wang, R., Schmidt, J.W., Harhay, D.M., Bosilevac, J.M., King, D.A., Arthur, T.M. 2017. Biofilm formation, antimicrobial resistance, and sanitizer tolerance of Salmonella enterica strains isolated from beef trim. Foodborne Pathogens and Disease. 14(12):687-695. https://doi.org/10.1089/fpd.2017.2319.
DOI: https://doi.org/10.1089/fpd.2017.2319

Interpretive Summary: Beef product contamination by Salmonella enterica is a serious public health concern, which may result in human infections and significant financial loss due to product recalls. To understand the mechanism and potential pathogen source responsible for Salmonella contamination in commercial meat plants, we characterized a wide variety of Salmonella strains isolated from contaminated beef trim regarding their ability to form biofilms (bacterial attachment and growth on solid surfaces), biofilm tolerance to common sanitizers, and their antimicrobial resistance. Our data indicate that the majority (86%) of these Salmonella strains were able to develop strong biofilms that were very tolerant to common sanitizers. A relatively high percentage (30%) of these strains was found resistant to multiple common antimicrobial agents, but this was not related to biofilm formation or sanitizer sensitivity. Collectively, these data indicate that strong biofilm forming Salmonella strains possess significant potential for causing meat product contamination which highlights the importance of proper and complete sanitization of food contact surfaces and food processing equipment in commercial meat plants.

Technical Abstract: In the beef industry, product contamination by Salmonella enterica is a serious public health concern, which may result in human infection and cause significant financial loss due to product recalls. Currently, the precise mechanism and pathogen source responsible for Salmonella contamination in commercial establishments are not well understood. We characterized 89 S. enterica strains isolated from beef trim with respect to their biofilm-forming ability, antimicrobial resistance, and biofilm cell survival/recovery growth after sanitizer exposure. A total of 28 Salmonella serovars was identified within these strains. The most common serovars identified were Anatum, Dublin, Montevideo, and Typhimurium, with these accounting for nearly half of the total strains. The vast majority (86%) of the strains was able to develop strong biofilms, and the biofilm-forming ability was highly strain dependent and related to cell surface expression of extracellular polymeric structures. These strains also demonstrated strong tolerance to quaternary ammonium chloride (QAC) and chlorine dioxide (ClO2), but were more sensitive to chlorine treatment. Sanitizer tolerance and bacterial postsanitization recovery growth were closely associated with strains' biofilm-forming ability. Thirty percent of the examined strains were found resistant to multiple antimicrobial agents and the resistance phenotypes were serovar associated, but not related to strains' biofilm-forming ability. Pulsed-field gel electrophoresis analysis tended to group strains by serovar rather than by biofilm-forming ability. Collectively, these data indicate that the strong biofilm formers of certain S. enterica strains/serovars possess significant potential for causing meat product contamination in meat processing environment.