RESEARCH ARTICLE Diversity of Bacterial Biofilm Communities on Sprinklers from Dairy Farm Cooling Systems

On dairy farms in hot climates worldwide, cows suffer from heat stress, which is alleviated by the use of water cooling systems. Sprinklers and showerheads are known to support the development of microbial biofilms, which can be a source of infection by pathogenic micro-organisms. The aim of this study was to investigate the presence of microbial biofilms in dairy cooling systems, and to analyze their population compositions using culture-indepen-dent technique, 16S rRNA gene sequencing. Biofilm samples were collected on eight dairy farms from 40 sprinklers and the microbial constituents were identified by deep sequencing of the 16S rRNA gene. A total of 9,374 operational taxonomic units (OTUs) was obtained from all samples. The mean richness of the samples was 465 ± 268 OTUs which were clas-sified into 26 different phyla; 76 % of the reads belonged to only three phyla: Proteobacteria, Actinobacteria and Firmicutes. Although the most prevalent OTUs (Paracoccus,Methylo-versatilis, Brevundimonas, Porphyrobacter, Gp4,Mycobacterium, Hyphomicrobium, Corynebacterium and Clostridium) were shared by all farms, each farm formed a unique microbial pattern. Some known potential human and livestock pathogens were found to be closely related to the OTUs found in this study. This work demonstrates the presence of bio-film in dairy cooling systems which may potentially serve as a live source for microbial pathogens