Biofilm Forming Bacteria in Meat Processing Facilities

Abstract

Industry environments could be a carrier of a wide range of microbial contaminants which can cause adverse effects on food deterioration as well as compromise the safety of food products. Meat processing facilities are particularly important as a potential source of contamination, not only with food spoilage bacteria but also with food-borne pathogens. Considering that, the cleaning process can remove 90% or more of microorganisms associated with the surface, but they cannot be completely destroyed with the cleaning process. Hence, the aim of this study was to determine residual bacteria after cleaning and disinfection and the ability of isolated strains for forming biofilms. Method: Swab samples from the food contact surfaces were taken after cleaning, washing and disinfection procedures. Sampling was conducted after cleaning and disinfection which increased the likelihood of targeting residential bacteria, according to the standard method using swab-sampler, with neutralizing buffer. Swabbing was conducted on 60 surfaces in meat processing facilities (slicing machines, cutting boards, knives or hatchets). From each surface of the equipment and tools, were performed microbiological analyses of aerobic plate count, total Enterobacteriacee count, Staphylococcus spp., Listeria monocytogenes, Pseudomonas spp., and Salmonella spp. following standard ISO methods. The results of the microbiological analyses were expressed as a number of bacteria per cm2 (CFU/cm2). Isolated microorganisms were further tested for biofilm-forming ability using biofilm biomass formation (crystal violet) assay at 25°C, the optical density of the wells was measured at 595 nm (OD595 nm).Results: The results showed that the washing and disinfection procedures were not effective enough to eradicate microorganisms in most retail facilities. Out of 60 swabs examined, 20 (33.3%) were positive to the presence of microorganisms. Next to high aerobic plate count and number of Enterobacteriaceae the most of the tested surfaces were positive to presence E. coli, (10), S. aureus (5), and Pseudomonas spp. (2). All tested isolates were capable of biofilm production on polystyrene microtiter plates after 48h incubation at 25°C but to various extents. The highest biofilm ability was shown in strains of Pseudomonas spp. followed by S. aureus, and E. coli. On the basis of the obtained ΔOD595 values at 25°C tested strains were classified into two categories – strong and moderate biofilm producers. At the temperature of 25°C Pseudomonas spp. and S. aureus isolates were classified as strong biofilm producers with ΔOD595 that ranged from 0.802 to 1.222. E. coli isolates were classified as moderate biofilm producers with ΔOD595 values that ranged from 0.301 to 0.418. According to results obtained, it can be concluded that proper sanitation will be a very important step for food safety. Disinfection and sanitation of food contact surfaces in meat processing facilities is a challenging task, aggravated by the great antimicrobial resistance of biofilm-associated bacteria. Furthermore, the existence of bacteria in biofilms in the food industry may cause cross- and post-process contamination and economic losses by reducing the shelf life of food products, increasing food spoilage, impairing heat transfer, and increasing corrosion rate.