Characterization of multispecies mixed biofilm communities at beef and pork processing plants and their impact on pathogen stress tolerance

Authors: Wang, Rong; CHITLAPILLY DASS, SAPNA - Texas A&M University; PALANISAMY, VIGNESH - Texas A&M University; ZHOU, YOU - University Of Nebraska; Katz, Tatum; Bosilevac, Joseph

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/13/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: E. coli O157:H7 and Salmonella enterica are two major pathogenic bacteria that cause foodborne illness in the U.S. These bacteria can form layers called biofilms to colonize on contact surfaces, which help them survive and may lead to contamination of meat products at processing plants. The ability of these bacteria to tolerate sanitization can change based on the processing facilities, the type of animals processed and the cleaning practices used. Most studies look at biofilms made by just one type of bacteria, but in reality, these bacteria often live in mixed communities. We studied biofilms from floor drains in three beef plants and two pork plants to investigate how the plant mixed biofilm communities affect these bacteria’s tolerance to sanitizers. We found that these pathogenic bacteria could easily join these mixed biofilms, even in the cold temperatures typical of processing plants. A multi-component sanitizer was effective at reducing the bacteria in most samples. However, bacteria in the pork plant biofilms survived and recovered better after cleaning than those in the beef plant biofilms. We observed that the contact surface texture might influence the biofilm structures and bacteria stress tolerance. Analyzing the bacteria communities showed no big differences in the types of bacteria between beef and pork plants, but there were differences in how much of each bacterial type were present. The mixed multiple types of bacteria at these plants and their interactions might affect how well the pathogens can tolerate sanitization. Research on cleaning methods and how they inactivate pathogens and prevent them from spreading in different processing plants should be reviewed individually for each type of facility.

Technical Abstract: E. coli O157:H7 and Salmonella enterica are the major foodborne pathogens in the United States. Biofilm formation has been found to potentially contribute to product contamination by these pathogens at meat processing facilities. Further, pathogen stress tolerance may vary significantly due to the interactions with the multispecies microbial community at meat plants, which may be affected by processing activity, animal species, and the local selective pressure caused by sanitization practices. Most current studies, however, have focused on single-species pathogen biofilms not taking into consideration that pathogens may be harbored in natural mixed biofilms. We characterized natural biofilms formed by microorganisms collected from floor drains at various areas at three beef plants and two pork plants and analyzed their impact on pathogen sanitizer tolerance. The pathogen strains were able to integrate into the mixed biofilms efficiently on contact surfaces even under low temperatures (7°C and 15°C) commonly seen in processing facilities. Cell density of colonized S. enterica (4.9 to 6.3 log10 CFU/chip) in mixed biofilms was higher than E. coli O157:H7 (3.2 – 5.2 log10 CFU/chip). Contact surface materials and meat plant types did not affect colonization of either pathogen species. A multi-component sanitizer exhibited high efficiency that reduced the integrated pathogen cells in most samples to a non-enumerable level. However, overall higher survival and post-sanitization recovery of pathogen cells were observed in the treated pork plant mixed biofilms than those in the beef plant samples. Scanning electron microscope analysis showed that the contact surface topography may impact mixed biofilm morphology and bacterial tolerance. Metagenomic analysis of the multispecies bacterial communities showed that Pseudomonadaceae, Halomonadaceae and Enterobacteriaceae were the three most abundant families across all samples. No significant difference in species compositions between the beef and pork plants or among the drain areas was observed. However, variations in the percentages of species’ relative abundance were observed among the samples. The multispecies microbial community at the processing plants and the resulting interspecies interactions could influence the tolerance level of the pathogens integrated into the mixed biofilms. Therefore, research reports on sanitization processes and the resulting pathogen inactivation and prevalence prevention that are described for the different types of processing facilities should be analyzed on a case-to-case basis.