Evaluation of biological activity and LC-MS fingerprinting of hydroalcoholic propolis extract against Staphylococcus aureus isolated from bovine mastitis

Abstract

Bacterial mastitis is a major disease in dairy cattle, leading to losses in milk production, quality, and animal health. Staphylococcus aureus is the main etiological agent of this disease, but treatment is challenging due to biofilm formation and antibiotic resistance. The present study aimed to characterize the chemical composition of the hydroalcoholic extract of propolis produced in a hive located in the municipality of Garanhuns, Pernambuco, Brazil, as well as to investigate its antimicrobial activity and the inhibition of biofilm formed by Staphylococcus aureus isolated from bovine mastitis. It was demonstrated that phenolic compounds in the propolis extracts ranged from 326.27 to 783.64 mgGAE/g and flavonoids from 267.16 to 815.65 mgQE/g. Chemical analysis by LC-MS indicated the presence of a phenolic acid (isochlorogenic acid), flavonoids (quercetin, isorhamnetin, baicalein and chrysin) and a phospholipid (oleoyl glycero-3-phosphocholine). The extract had a minimum inhibitory concentration against Staphylococcus aureus strains of 31.25 and 62.5 µg/mL and a minimum bactericidal concentration of 125 and 250 µg/mL. In the biofilm inhibition assay of Staphylococcus aureus isolates from bovine mastitis, no significant effect was found in the biofilm inhibition test (p > 0.05) among the concentrations of the propolis extract tested but all inhibited biofilm sufficiently to reduce the number of samples in the “strong biofilm producer” category. The assessment of the propolis extract’s capacity to disaggregate biofilms demonstrated little effectiveness at the concentrations tested and no capacity to eradicate the structure. The results demonstrate that the propolis extract analyzed has antimicrobial and antibiofilm properties, suggesting pharmaceutical potential.