Location: Meat Safety and Quality
Title: Survival of Salmonella enterica and E. coli O157:H7 in environmental biofilms isolated from pork plants as compared to beef plantsAuthor
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Submitted to: Safepork
Publication Type: Abstract Only Publication Acceptance Date: 1/30/2023 Publication Date: 5/15/2023 Citation: Wang, R., Bosilevac, J.M. 2023. Survival of Salmonella enterica and E. coli O157:H7 in environmental biofilms isolated from pork plants as compared to beef plants. [Abstract. Safepork. 14(1). Interpretive Summary: Technical Abstract: Background: S. enterica and E. coli O157:H7 are leading causes of foodborne illness in the U.S. Biofilm formation by these pathogens may play an important role in meat contamination. Previous studies suggested that certain S. enterica and E. coli O157:H7 strains may be better at adapting to the processing environment with stronger survival ability via mixed biofilm formation with natural microbial communities and subsequently, a higher chance of causing contamination. Our recent study using natural multispecies biofilms recovered from a processing plant experiencing an increased O157 prevalence showed these processing plant environmental biofilms recruited and protected E. coli O157:H7 to a significantly greater extent than the natural biofilms recovered from a control plant not experiencing similar problems, implying that the plant environment microbial communities may pose the potential to enhance pathogen survival and persistence. Current sanitization studies mostly focus on single-species pathogen biofilms but do not take into consideration that pathogens can be harbored in natural mixed biofilms which are commonly seen in commercial plants. Sanitizer effectiveness can vary significantly due to the interactions between the processing plant environmental microorganisms and the pathogens. Furthermore, in addition to biofilm cell inactivation, post-sanitization pathogen survival control and prevalence prevention are all essential for reducing biofilm–related cross-contamination. Here we evaluated the effectiveness of novel sanitizer products against pathogens harbored in natural mixed biofilms isolated from pork and beef plants, and further examined the impact of the microbial communities present in the different processing environments on pathogen survival and post-sanitization prevalence. Method & Methods: Two pork plants and three beef plants were selected for environmental sample collection. Floor drains located at areas of the fabrication room and cooler of the pork plants and processing floor, cooler, or hotbox of the beef plants were sampled. Biofilm formation by these samples was determined on 96-well polystyrene plates using the crystal violet staining method. To evaluate sanitizer effectiveness against S. enterica or E. coli O157:H7 harbored within environmental mixed biofilms, an S. enterica or E. coli O157 cocktail was prepared by mixing equal volumes of overnight cultures of five S. enterica strains of various common serovars (Anatum, Dublin, Montevideo, Newport, Typhimurium) or five E. coli O157:H7 strains that were all isolated from trim samples at commercial plants. The floor drain samples were enriched and allowed to form mixed biofilms on stainless steel (SS) or tile chips with the co-inoculation of the S. enterica or E. coli O157:H7 cocktail under processing temperature (7oC). A multi-component sanitizer and an enzyme-based detergent were tested against the pathogens colonized in mixed biofilms following the manufacturers’ instructions using foam coverage or fog treatment. The ability of the mixed biofilms to recruit and/or protect from the treatments’ co-inoculated pathogen cells was determined. Further, biofilm morphology before and after treatment with the enzyme-based detergent was directly visualized using a scanning electron microscope (SEM) to better understand its functional mechanism. DNA extraction and 16S rRNA gene amplicon metagenomic analysis was performed to analyze and compare the microbial communities collected from the pork and the beef plants to determine if the environmental community compositions as the result of the different processing operations are related to the observed phenotypic difference. Results: All pork plant samples formed strong biofilms whereas variations in the biofilm-forming ability of the beef plant samples were observed, which depended upon the plants and drain |
