Screening of surface properties and antagonistic substances production by lactic acid bacteria isolated from the mammary gland of healthy and mastitic cows.

Bovine mastitis (BM) is a costly disease in dairy cattle production. The prevention and treatment of mastitis is performed by applying antimicrobial products that negatively affect milk quality. In the last years, the use of probiotic microorganisms to prevent infections in humans and animals has being aggressively studied. Samples from teat canal and milk (foremilk and stripping) were taken from healthy and mastitic mammary quarters. A screening of the surface properties and antagonistic substances production of lactic acid bacteria (LAB) isolated from the mammary gland was performed to select potential probiotic strains to prevent mastitis. Somatic cell count, physico-chemical and microbiological studies were carried out. Pre-selected microorganisms were genetically identified. Compared with stripping milk, foremilk showed lower levels of fat and higher levels of pH, density, microorganism numbers, lower percentage of strains with mean and high hydrophobicity and mean autoaggregation and higher number of strains able to produce hydrogen peroxide and bacteriocins. The other parameters analyzed were not statistically significant. One hundred and two LAB strains were isolated. Most of them had low degrees of hydrophobicity and autoaggregation. No correlation between these properties was found. Antagonistic metabolites were mainly produced by strains isolated from healthy quarters. Most of the pre-selected strains were identified as Streptococcus bovis and Weissella paramesenteroides. Three bacteriocin-producers were found and their products partially characterized. The results of this work are the basis for the further design of a specie-specific probiotic product able to prevent BM.