Industrial surfaces of poultry and fish slaughterhouses as reservoirs of viable microorganisms after sanitation

This study identified and characterized the viable and culturable bacterial diversity present on surfaces and equipment in poultry ( n = 50) and fish (n = 50) slaughterhouses after pre-operational sanitation. In total, 271 bacterial isolates (poultry = 169; fish = 102) were identified using MALDI-TOF MS. In the poultry slaughterhouse, the most frequent genera were Serratia (16%), Staphylococcus (14.8%), Kocuria (14.8%), Aeromonas (7.1%), and Lelliottia (7.1%), while in fish processing, Enterobacter (17.6%), Acinetobacter (12.7%), Staphylococcus (11.8%), Rothia (9.8%), and Klebsiella (5.9%) predominated. Adhesion assays revealed significant differences between plant types: 39.6% of the poultry isolates were adherent, predominantly with weak adhesion, whereas 98% of the fish isolates adhered, mostly with moderate intensity. Biofilm susceptibility tests to peracetic acid showed that 44.9% and 27% of the isolates tolerated the sanitizer at 300 ppm and 750 ppm, respectively, indicating greater efficacy at the higher concentration. Overall, the predominant genera not only exhibited a higher number of adherent isolates but also demonstrated tolerance to peracetic acid, particularly Serratia , Kocuria , and Staphylococcus in the poultry processing plant, and Enterobacter , Acinetobacter , Staphylococcus , and Klebsiella in the fish processing plant. The findings of this study demonstrate that even after pre-operational sanitation, different microorganisms can persist on industrial surfaces, highlighting the ecological complexity of these environments and reinforcing the need for more effective sanitation strategies to improve microbial control in the food industry. • Viable bacteria persisted on poultry and fish surfaces after sanitation. • Fish isolates showed higher adhesion than poultry isolates. • Predominant genera showed both adhesion ability and tolerance to peracetic acid. • Peracetic acid at 750 ppm was more effective, but did not fully eliminate biofilms.