In vitro studies to characterize probiotic properties of lactic acid bacteria isolated from bovine milk

MATIAS PELLEGRINO; IGNACIO FROLA; MARIA ELENA FÁTIMA NADER; CRISTINA BOGNI

Tucuman

Simposio; IV Simposio Internacional de Bacterias Lacticas (SIBAL); 2013

CERELA-CONICET

Bovine Mastitis is one of the most prevalent and expensive diseases of dairy cows. This disease is associated to distress to the animal and decreased milk production. An interesting alternative approach to prevent bovine mastitis is the intramammary application of microorganisms with probiotic properties, in order to restore the ecological balance of the udder and protect the host. In a previous report, 219 lactic acid bacteria (LAB) strains were isolated from bovine milk of dairy herds from Córdoba and Tucumán. Nine LAB were selected as potential probiotic due to their high hydrophobicity, moderately autogregation, production of lactic acid, hydrogen peroxide and bacteriocins. The aim of the present study was to characterize probiotic properties of the selected LAB for its possible inclusion in a probiotic product for the prevention of bovine mastitis in the dry period of the cow. We investigated: a) In vitro inhibitory capacity by the cross-striations technique in 1.2 % LAPTg agar against 20 microorganisms considered as major bovine mastitis causing pathogen and 15 bacteria isolated from indigenous microbiota of the teat canal, b) LAB ability to co-aggregate different mastitis pathogens by co-culture in MRS medium c) Adhesion of LAB to epithelial cells of the teat canal (ECTC). The results shown that LAB were able to inhibit, in different degrees (low, intermediate and high), the 100% of the bovine mastitis pathogens assayed. Six LAB showed intermediate inhibition greater than 80% for Staphylococcus aureus, Streptococcus dysgalactiae, Streptococcus agalactiae and Streptococcus uberis. The remaining strains showed low inhibition. Eight BAL showed high inhibition percentages of pathogens in combination with a low inhibition of indigenous bacteria microbiota. Respect to co-aggregation assays, all BAL strains were able to co-aggregate 95% of the bovine mastitis pathogens being S. aureus, S. agalactiae and S. uberis those with higher degree of co-aggregation. Six of the nine LAB showed percentages of adhesion to ECTC higher than 85%. The results allowed selecting 3 LB: Lactobacillus perolens CRL1724, Lactococcus lactis subsp lactis CRL 1655 and Enterococcus hirae CRL1836. These strain showed the following characteristics: high co-aggregation to bovine mastitis pathogens, high percentages of adherence to ECTC, moderate to high inhibition of bovine mastitis pathogens and low inhibition of indigenous bacteria microbiota. It also highlights the ability of L. lactis subsp CRL 1655 and L. lactis perolens of CRL1724 to produce bacteriocins and high lactic acid concentration, respectively. The results obtained in this study indicate that the 3 LAB selected could be considered as potential strains for inclusion in a probiotic veterinary product for the prevention of bovine mastitis during the dry period.