Avaliação in vitro da atividade antimicrobiana do extrato de própolis verde contra bactérias patogênicas

Abstract

This study aimed to evaluate the antimicrobial activity of six commercial samples of green propolis extract against four bacterial strains from the American Type Culture Collection (ATCC): Escherichia coli (ATCC 25922), Klebsiella pneumoniae (ATCC 700603), Pseudomonas aeruginosa (ATCC 27853), and Staphylococcus aureus (ATCC 25923). The microorganisms were cultivated on MacConkey agar and Mannitol Salt agar and incubated at 36ºC for 24 hours. After growth, they were transferred to tubes containing sterile physiological solution (0.85% NaCl) until turbidity reached the 0.5 McFarland standard and then inoculated onto Mueller-Hinton agar. Antimicrobial activity was evaluated using the agar diffusion technique, employing seven wells filled with green propolis samples and the negative control, in addition to a positive control performed with an amoxicillin-clavulanic acid disk. The experiments were carried out in duplicate, and antimicrobial activity was determined by measuring the diameters of the inhibition zones. The results demonstrated that only the Gram-positive bacterium (S. aureus) had its growth inhibited by the green propolis samples, whereas the Gram-negative isolates showed no halo formation. All tested samples demonstrated activity against S. aureus, with inhibition zones ranging from 19 mm to 28 mm, highlighting sample number 3 of the alcoholic extract, which presented the largest inhibition zones (28 mm). Alcoholic extracts demonstrated slightly larger inhibition zones compared to aqueous extracts. The negative control showed no activity, whereas the positive control inhibited 100% of the tested strains. In conclusion, the findings demonstrate the antimicrobial potential of green propolis against S. aureus, reinforcing the importance of valuing natural products and indicating the need for future studies aimed at the development of complementary therapeutic alternatives.