IS BOVINE MASTITIC BACTERIOME SENSITIVE TO PLANT EXTRACTS?

Summary

Abstract
One of the most impacting diseases of dairy cows worldwide, due to the difficulties to diagnose subclinical development and to treat the clinical disease is represented by mastitis. In this study the several plant extracts and essential oils were assessed for antimicrobial efficacy on bacteria isolated from subclinical cases of mastitis.
Milk samples were obtained from Romanian Spotted extensively raised dairy cows (n=20), cohabiting on the same farm with sheep and pigs, which were diagnosed with subclinical mastitis. The microbiome components were identified by use of classical bacteriological methods and cultivated against Melissa officinalis and propolis alcoholic extracts and essential oils of Rosmarinus officinalis, Thymus vulgaris and Lavandula angustifolia in the Kirby-Bauer well diffusion method.
S. sciuri, Staphylococcus spp, E. coli, Enterococcus faecium were isolated from the milk samples, showing a high MAR index, thus eliminating the possibility of therapy with 12 of the 14 antibiotics tested in some isolates.
The best antibacterial effect was shown by Thymus vulgaris essential oil (25±5.6 mm inhibition) versus the weakest effect of Lavandula angustifolia essential oil (17.5±8.2mm inhibition). Staphylococcus spp. showed the highest sensitivity, while E.coli strains were much more resistant. When compared to the essential oil the Melissa tincture was less effective (11.3±3.6mm versus 12.3±4.3mm) but comparable to amoxicillin, amoxicillin/clavulanic acid and stronger than cefoperazone. The propolis extracts used to control bacterial growth have shown in vitro efficacy, the effect depending on the concentration used.
Both tincture and essential oils proved to be efficient depending more on the strain than on the solvent type. These results are opening the prospect of using plant extracts, essential oils and propolis as an alternative to antibiotics in the treatment of mastitis, leading to safer products, with less antibiotic residues in milk.
Keywords: subclinical mastitis, microbiome, antibiotic resistance, medicinal plants, dairy cows