IN VITRO STUDIES TO CHARACTERIZE BENEFICIAL PROPERTIES OF LACTIC ACID BACTERIA ISOLATED FROM BOVINE MILK

PELLEGRINO, M. (EXPOSITOR); FROLA, I.; NADER-MACIAS, MEF; BOGNI, C.

San Miguel de Tucumán

Simposio; IV International Symposium on Lactic Acid Bacteria: Food, Health and Applications; 2013

CERELA-CONICET

Bovine Mastitis is one of the most prevalent and expensive diseases of dairy cows, associated to distress to animal and a decreasement of milk production. An interesting alternative approach to prevent bovine mastitis is the intramammary application of microorganisms with beneficial properties, in order to restore the ecological balance of the udder and to protect the host from pathogens. In a previous report, 219 lactic acid bacteria (LAB) strains were isolated from bovine milk of dairy herds from Córdoba and Tucumán. Nine LAB strains were selected as beneficial microorganisms by their high hydrophobicity, moderate auto aggregation, production of lactic acid, hydrogen peroxide and bacteriocins. The aim of the present study was to characterize the beneficial properties of the selected LAB for their possible inclusion in a product for the prevention of bovine mastitis in the dry period of the cow. The studies performed were: 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 obtained have shown that LAB were able to inhibit, in different degrees (low, intermediate and high), all the bovine mastitis pathogens assayed. Six LAB strains showed intermediate inhibition higher than 80% for Staphylococcus aureus, Streptococcus dysgalactiae, Streptococcus agalactiae and Streptococcus uberis. The rest of the strains showed low inhibition. Eight BAL strains evidenced a high inhibition percentage of pathogens in combination with a low inhibition of indigenous bacteria microbiota. Referred to co-aggregation assays, all the BAL strains were able to co-aggregate in 95% the bovine mastitis pathogens, being S. aureus, S. agalactiae and S. uberis those with a higher degree of co-aggregation. Six of the nine LAB strains showed percentages of adhesion to ECTC higher than 85%. The results obtained have allowed toselect 3 LAB strains with beneficial characteristics: Lactobacillus perolens CRL1724, Lactococcus lactis subsp lactis CRL 1655 and Enterococcus hirae CRL1836. These strains showed some specific characteristics: high co-aggregation with bovine mastitis pathogens, high percentages of adherence to ECTC, moderate to high inhibition of bovine mastitis pathogens and compatibility with indigenous bacteria microbiota. The ability of L. lactis subsp CRL 1655 and L. lactis perolens CRL1724 to produce bacteriocins and high levels of lactic acid respectively was also evidenced, as potential beneficial strains for the bovine mammary gland. 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.