Hidden threats: exploring biofilm communities in broiler houses and pig nursery units drinking water lines

Drinking water systems (DWS) are often an overlooked source of microbial contamination of drinking water in broiler and piglet production. Persistent biofilms within water lines can act as reservoirs of contamination, reintroducing microorganisms into the flowing water and potentially compromising animal health. This study investigates the microbial composition of biofilms in the DWS of broiler houses and pig nursery units, their impact on drinking water quality, and the influence of the source water on both water quality and biofilm communities. The bacterial load of DWS biofilm swabs, collected at the end of production cycles before cleaning and disinfection was evaluated, and the dominant bacterial taxa were identified. Furthermore, 16S gene metabarcoding was applied to the biofilm samples. No significant differences in microbial load were observed between the two sectors, with a median total aerobic count of 3.6 log CFU/cm2. Enterococci, a faecal indicator, were detected in 80% of all samples. Moreover, Escherichia coli was found more frequently in broiler houses (47%) than in pig nursery units (27%). The two dominant identified genera were Staphylococcus and Pseudomonas. The Staphylococcus saprophyticus species was the most frequently identified isolate, accounting for 10.6% of all isolates across both broiler houses and pig nursery units. In broiler houses, the next most frequently identified species were Pseudomonas aeruginosa (5.6%) and Stenotrophomonas maltophilia (5.3%). In contrast, in pig nursery units, Pseudomonas fluorescens (6.3%) and Psychrobacter faecalis/pulmonis (5.5%) were most frequently identified. Research showed that the drinking water microbial community not only depended on the source water but was also influenced by biofilms in DWS, as similar bacterial taxa were found in both the drinking water at the drinking nipples and in biofilms on water-contact surfaces. The presence of faecal indicator bacteria and potential animal pathogens underscores the risks associated with the biofilms. These biofilms can contaminate drinking water to animals, underscoring the need for targeted strategies to monitor and mitigate biofilm formation.