No abstract

Bovine mastitis is the most important infectious disease on dairy farms. Conventional antibiotic therapy is often unsatisfactory and alternative treatments are continually under investigation. Lactobacillus (Lb.) perolens CRL 1724 and Lactobacillus plantarum CRL 1716 were previously isolated from milk of dairy cows and selected according to their potential probiotic properties. In the present work the in-vitro capacity of Lactobacillus strains to adhere to bovine teat canal epithelial cells (BTCEC) and to inhibit and co-aggregate 14 mastitis-causing pathogens (MCPs) was investigated. The effect of Lb. perolens CRL 1724 after intramammary inoculation in lactating cows was evaluated through determination of clinical signs of mastitis, milk appearance, somatic cell counts and Lb. perolens CRL 1724 recovery from milk. Lb. perolens CRL 1724 was able to inhibit 12 of 14 MCPs (85·7%) in vitro, especially those considered to be major pathogens. In addition, Lb. perolens CRL 1724 co-aggregated with all of them. Lb. plantarum CRL 1716 was able to inhibit 7 of 14 MCPs (50%) in vitro and showed co-aggregation ability similar to Lb. perolens CRL 1724. Lb. perolens CRL 1724 showed a higher efficacy of adhesion to BTCEC (values of percentage of adhesion and adhesion index of 75% and 14·4, respectively) than Lb. plantarum CRL 1716 (37% and 7·4, respectively). Lb. perolens CRL 1724 was recovered from all mammary quarters and no clinical signs or teat damage were observed after the inoculation of 106 cfu/ml. The udders presented a normal aspect and there were no changes in the appearance of the milk. The results obtained will serve as the basis for further trials to evaluate the potential of Lb. perolens CRL 1724 to be included in a non-antibiotic formulation for the prevention of bovine mastitis.

Bovine mastitis causes economic losses on dairy farms worldwide. Lactic acid bacteria (LAB) in animal health are an alternative tool to avoid antibiotic therapy on the prevention of bovine mastitis. In previous studies, 12 LAB isolated from bovine milk were selected taking into account some of the following characteristics: hydrophobicity, auto aggregative capability, inhibition of indicator pathogens, hydrogen peroxide, and capsular polysaccharide production. These LAB were considered because of their beneficial properties. In this work, we also analyzed the antimicrobial activity and the co-aggregation against mastitis causing bacteria, auto-inhibition, adhesion to bovine teat canal epithelial cells (BTCEC), and growth kinetic curves for the 12 LAB. Two of them, Lactococcus lactis subsp. lactis CRL 1655 and Lactobacillus perolens CRL 1724, were selected because they had an interesting pattern of adhesion to BTEC, the inhibition of pathogens and the co-aggregation with the 100% of the assayed pathogens. They showed a predictable difference in the PFGE genomic pattern bands. The kinetic growth of these two strains was similar between them and with the rest of the assayed LAB. The strains selected in the present study showed indispensable characteristics for their inclusion in a probiotic formulation to be used at dry-off period for the prevention of bovine mastitis.

The effect of intramammary inoculation of Lactobacillus perolens CRL 1724 on bovine udders at drying off was evaluated through histological examination of the canal and cistern tissues. The persistence of the strain in the udder 7 d post inoculation was also determined. Lb. perolens CRL 1724 was recovered from all mammary quarters and no clinical signs or teat damage were observed after inoculation of 10(6) cfu/ml. The udders showed a normal structural aspect and there were no modifications of the milk appearance. Lb. perolens CRL 1724 cells were evidenced on the surface of the epithelial cells of the cistern without causing any morphological modifications or cell alterations. Lb. perolens CRL 1724 produces a mild inflammatory reaction, characterized by recruitment of neutrophils to the epithelial zone and a slight hyperaemia into blood vessels. This preliminary study provides important information for further studies directed towards the inclusion of Lb. perolens CRL 1724 in the design of probiotic products for preventing bovine mastitis in non-lactating dairy cows.