Microbial Dynamics in Mixed-Culture Biofilms of Salmonella Typhimurium and Escherichia coli O157:H7 and Bacteria Surviving Sanitation of Conveyor Belts of Meat Processing Plants

Citation

Yang, X., Wang, H., Hrycauk, S., Holman, D.B., Ells, T.C. (2023). Microbial Dynamics in Mixed-Culture Biofilms of Salmonella Typhimurium and Escherichia coli O157:H7 and Bacteria Surviving Sanitation of Conveyor Belts of Meat Processing Plants. Microorganisms, [online] 11(2), http://dx.doi.org/10.3390/microorganisms11020421

Plain language summary

Biofilm formation can lead to the persistence of Salmonella Typhimurium (ST) and E. coli O157:H7 (O157). Even though equipment using in food processing facilities is routinely cleaned and sanitized, but the objective is not to have bacteria-free surface. Thus, the , meat processing environment is conducive for multi-species biofilm formation. This study investigated the impact of meat processing surface bacteria (MPB) on biofilm formation by O157 (non-biofilm former; NF) and ST (strong biofilm former; BF). MPB recovered from different surfaces of a conveyor belt were co-inoculated with the two pathogens or delayed by 48 h for development of biofilms on stainless coupons. The mean counts for O157 and ST under equivalent conditions mostly did not differ. Pseudomonas dominated the MPB inocula and biofilms, regardless of MPB type or development mode. Whether or not a pathogen is deemed BF or NF in monoculture, its successful integration into complex multi-species biofilms ultimately depends on the presence of certain other residents within the biofilm. The findings of this work show that for pathogen control in meat processing facility, we should not depend on the biofilm forming ability of monocultures, but rather take a holistic approach to reduce surface contamination with bacteria as much as possible.

Abstract

Biofilm formation can lead to the persistence of Salmonella Typhimurium (ST) and E. coli O157:H7 (O157). This study investigated the impact of meat processing surface bacteria (MPB) on biofilm formation by O157 (non-biofilm former; NF) and ST (strong biofilm former; BF). MPB were recovered from the contacting surfaces (CS), non-contacting surfaces (NCS), and roller surfaces (RS) of a beef plant conveyor belt after sanitation. O157 and ST were co-inoculated with MPB (CO), or after a delay of 48 h (IS), into biofilm reactors containing stainless steel coupons and incubated at 15 °C for up to 144 h. Coupons were withdrawn at various intervals and analyzed by conventional plating and 16S rRNA gene amplicon sequencing. The total bacterial counts in biofilms reached approximately 6.5 log CFU/cm2, regardless of MPB type or development mode. The mean counts for O157 and ST under equivalent conditions mostly did not differ (p > 0.05), except for the IS set at 50 h, where no O157 was recovered. O157 and ST were 1.6 ± 2.1% and 4.7 ± 5.0% (CO) and 1.1 ± 2.2% and 2.0 ± 2.8% (IS) of the final population. Pseudomonas dominated the MPB inocula and biofilms, regardless of MPB type or development mode. Whether or not a pathogen is deemed BF or NF in monoculture, its successful integration into complex multi-species biofilms ultimately depends on the presence of certain other residents within the biofilm.

Publication date

2023-02-01