Bovine mastitis, an inflammatory disease of the mammary gland often associated to bacterial infection, is the first cause of antibiotic use in dairy cattle. Because of the risk of antibioresistance emergence, alternative non-antibiotic strategies are needed to prevent or to cure bovine mastitis and reduce the antibiotic use in veterinary medicine. In this work, we investigated Lactococcus lactis V7, a strain isolated from the mammary gland, as a probiotic option against bovine mastitis. Using bovine mammary epithelial cell (bMEC) culture, and two representative strains for Escherichia coli and for Staphylococcus aureus, two major mastitis pathogens, we investigated L. lactis V7 ability to inhibit cell invasion (i.e. adhesion and internalization) of these pathogens into bMEC. L. lactis V7 ability to modulate the production of CXCL8, a key chemokine IL-8 responsible for neutrophil influx, in bMEC upon challenge with E. coli was investigated by an ELISA dosage of CXCL8 in bMEC culture supernatants. We showed that L. lactis V7 inhibited the internalisation of both E. coli and S. aureus strains into bMEC, whereas it inhibited the adhesion of only one out of the two S. aureus strains and of none of the E. coli strains tested. Investigation of the bMEC immune response showed that L. lactis V7 alone induced a slight increase in CXCL8 production in bMEC and that it increased the inflammatory response in bMEC challenged with the E. coli strains. Altogether these features of L. lactis V7 make it a potential promising candidate for a probiotic prevention strategy against bovine mastitis.

The potential of in vitro probiotic Lactobacillus spp. was evaluated in fermented milks marketed in Belo Horizonte, MG, Brazil. Of the samples analyzed, 86.7% had at least 10(6) CFU/mL of Lactobacillus spp., complying with the Brazilian quality standards for fermented milks. Furthermore, 56.7% had minimum count ranging from 10(8) to 10(9) CFU/mL, which is in accordance with legal parameters. The remaining 43.3% would not be able to satisfactorily guarantee benefits to consumers. The amount of Lactobacillus spp. varied between batches of products, which may indicate failures in monitoring during manufacture, transport or storage. All strains of Lactobacillus spp. showed some inhibitory activity against the indicator microorganisms, being more pronounced against pathogenic microorganisms than against non-pathogenic (P<0.05). Samples of Lactobacillus spp. showed different profiles of antimicrobial susceptibility, with an occurrence of cases of multidrug resistance. All strains tested showed sensitivity to bile salts (0.3%) and resistance to gastric pH (2.0). Lactobacillus spp. of commercial fermented milks should be present in higher amounts in some brands, be resistant to bile salts and have no multiple resistance to antimicrobials.