Antimicrobial activity of Lactobacillus spp. strains against pathogens causing bovine mastitis

Abstract

Treatment of bovine mastitis with antibiotic generates residues in milk that affects the quality of dairy products for the population feeding. The lactic acid bacteria have been proposed as an alternative to avoid use of antibiotics. The in vitro antimicrobial activity of six strains of Lactobacillus spp. was evaluated against bovine mastitis pathogens by diffusion on agar layers and disk diffusion of the supernatant. After neutralization with NaOH and heat (100 and 121°C for 5 min) and enzymatic treatments, the antagonistic activity of the cell-free supernatants of the three strains studied remained active. The inhibitory substances lactic acid (1.08 - 2.68 g.l-1) and hydrogen peroxide (0.05 - 0.26 g.l-1) were quantified. Four strains showed inhibitory potential against pathogenic strains of Staphylococcus spp. causing mastitis. The strain ML5 stood out for having greater inhibition halos (54-65 mm) against clinical isolates of pathogens such as Staphylococcus chromogenes and Staphylococcus hyicus, and, thus, showed to be a potential candidate to be evaluated in the prevention of bovine mastitis.

Key words: antagonism BAL, antimicrobial peptides, Streptococcus agalactiae, Staphylococcus aureus, Staphylococcus chromogenes, Staphylococcus hyicus.