Susceptibility of Staphylococcus spp. Isolated from Milk of Goats with Mastitis to Antibiotics and Green Propolis Extracts

The antimicrobial activity of ethanolic and aqueous extracts of a commercial green propolis and of 13 standard antibiotics was evaluated against Staphylococcus spp. strains isolated from milk of goats with mastitis. More than 95% of the isolates were sensitive to cephalothin and tetracycline, whereas only 28.9% were sensitive to streptomycin. All the isolates were susceptible to both ethanolic and aqueous extracts, but the former showed the higher antimicrobial activity. The larger mean diameter of the inhibition zone of coagulase-negative staphylococci (15.5 mm) was in fact obtained with the ethanolic extract. A Minimum Inhibitory Concentration of 50 μg/mL of both extracts was determined, which highlighted a promoting in vitro activity.