Evaluation of bioflm formation by bacterial strains isolated from milking equipment and milk samples from cows with mastitis

Abstract

The presence of bioflm-forming bacteria from the mammary gland of dairy cows adhered to equipment in the milking environment represents one of the major causes of bacterial resistance during mastitis treatment. The aim of this study was to identify strains of Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli in milk samples from cows with mastitis, as well as in the expansion tank and milking set liners. We aimed to quantify the extracellular proteins and polysaccharides in the bioflm produced by each strain. A total of 294 samples were collected from a dairy farm in the municipality of Uberlândia, Minas Gerais. To identify the S. aureus, S. epidermidis and E. coli isolates responsible for bioflm production, we tested the phenotype using the Congo red agar (CRA) and microplate adhesion tests. Protein quantifcation was performed with a Bicinchoninic Acid Protein Assay Kit (BCA kit), and polysaccharides were quantifed by the phenol sulfuric acid method. We identifed eight strains of S. aureus, one strain of S. epidermidis and 11 strains of E. coli responsible for bioflm production, all of which showed a higher concentration of polysaccharides than proteins in the matrix. Escherichia coli was considered the most prevalent bacterium among the samples, and S. aureus was determined to be the largest bioflm producer. The results of the CRA and microplate adhesion tests were similar in regard to identifcation of the bioflm-producing strains according to their phenotype and matrix composition. The classifcation of S. aureus strains as major bioflm producers is of great concern for producers, as such bacteria are considered one of the predominant contagious etiological agents that cause bovine mastitis. In addition, our observation that E. coli and S. epidermidis can produce bioflms highlights the need to reassess prophylactic measures to avoid the adhesion of bioflm-producing bacteria.