Abstract
Broiler processing environments are a source of spoilage bacteria and potential pathogens. The aim of this study was to investigate the impact of cleaning and disinfection (C&D) on bacterial load and diversity in two broiler processing plants and to determine the efficacy of industry-standard disinfectants (DIs). C&D significantly reduced average bacterial loads on surfaces from 3.7 to 1.8 log CFU/cm2 in Plant A and from 7.0 to 3.8 log CFU/cm2 in Plant B (P < 0.001). Metataxonomics revealed that Acinetobacter and an unknown Enterobacteriaceae genus dominated before C&D in Plants A and B, respectively, while Pseudomonas was predominant after C&D in both plants. Bacterial diversity only declined significantly after C&D in Plant B. Bacterial loads also declined across hygienic zones along the broiler processing line in Plant A. During slaughter, Staphylococcus, Lactobacillus, and Anoxybacillus dominated, and bacterial loads were significantly higher compared with post-slaughter zones, which were dominated by Pseudomonas. Culture-dependent analyses confirmed the presence of Pseudomonas spp. and also bacteria affecting food safety, including Listeria monocytogenes, Escherichia coli, Yersinia enterocolitica, Acinetobacter baumannii, and Pseudomonas aeruginosa. A selection of these was tested against DIs using robotic high-throughput screening. At the recommended user concentrations, DIs effectively inhibited planktonic bacteria and significantly reduced mono-species biofilms. However, none of the DIs completely eradicated all biofilms at these concentrations, with survival rates ranging from 7% to 53%, depending on the DI. In conclusion, C&D effectively reduces the bacterial burden and reshapes the bacterial microbiota with incomplete biofilm eradication by commercial DIs.