CONICET | Buscador de Institutos y Recursos Humanos

Bovine mastitis is responsible of major economic losses on dairy farms worldwide. Several investigations are directed to the finding of different methods to prevent bovine mastitis. An novel alternative to prevent the disease is the intramammary application of microorganisms with probiotic properties. The genus Lactobacillus is one of the most applied to restore the ecological balance of mucous and to protect the host. In previous studies, the isolation and characterization of a strain of Lactobacillus perolens from milk of healthy dairy cows was reported. This strain was considered as potentially probiotic because of high hydrophobicity index, moderately autoagregation, organic acid production and inhibition of S. dysgalactiae and S. uberis. In the present work, the in vitro inhibitory effect of L. perolens against the indigenous mirobiota of the teat canal was performed, and through in vivo assays, the behaviour after its intramammary infusion in lactating cows was determined. For the in vitro inhibitory activity assay, the cross striations technique in LAPTg 1.2% agar was used, in which L. perolens was evaluated against the indigenous microbiota previously characterized as Staphylococcus spp., Enterococcus spp., Bacillus spp. no coliform enterobacterias and Pseudomonas spp. For the in vivo assay, 3-lactating cows free of pathogens and somatic cell count (SCC) < 200,000 cells/ml, were used. Three quarters of each udder were inoculated with 2 x 106 cfu/ml of L.perolens. Individual samples were collected from foremilk on days 0 and 1, before and after inoculation, respectively, and on days 2, 5, 7 and 15 thereafter. For each sample RCS, bacteriology in blood agar (5%) and recovery of L perolens on MRS plates with 10 µg streptomycin, was determined. Clinical signs (redness, temperature and pain) were also recorded. A high percentage of intermediate inhibition (86,6%) was observed after in vitro cross striations of L. perolens and the indicator microorganisms. After the intrammary inoculation, L. perolens was recovered from 88,9%, 77,8% and 55,6% of the quarters inoculated on days 1, 2 and 7, respectively, and 22,2% of the quarters at the end of the experience. A significant increase (1,8 x 106 cel/ml and 1,2 x 106 cel/ml) in the SCC was observed on days 1 and 2 post-inoculation, respectively, while at day 5 cells counts returned to a normal value. No clinical signs were observed in the inoculated udders and the milk from these quarters was normal. The results obtained in this work, are the basis to further study L. perolens as a potential strains for its inclusion in a probiotic product for the prevention of bovine mastitis. According to these results, and knowing the high susceptibility of lactating cows to bovine mastitis during the dry period, the intramammary application of L. perolens in cows during this period will be subject of study.