Antibiotics are the elective drugs in
bovine mastitis (BM) treatment, despite their low rates of efficiency and effectiveness and increasing risk of pathogen resistance. In this sense, it is urgent to discover new and effective
antimicrobial agents to apply in BM control and even treatment.
Plant extracts have been widely recognized as a rich source of
phytochemicals with antimicrobial potential. Thus, the present work aims to compare the bioactivity of Eucalyptus globulus and Juglans regia extracts against Staphylococcus aureus
bovine mastitis strains with
penicillin G. At non-toxic concentrations, E. globulus exerted a bacteriostatic effect in planktonic cells and J. regia had no antimicrobial activity.
Penicillin G, at minimum inhibitory concentration (MIC), demonstrated bactericidal activity, but just for S. aureus 3, 5, 6 and ATCC 25923, while the other strains seem to have acquired resistance. On the other hand, E. globulus and
penicillin G in combination demonstrated synergy, being the most effective approach against S. aureus 1, 2 and 4. Thus,
penicillin alone and in combination with E. globulus or J. regia seems to be promissory strategies to control
bovine mastitis infections.