Antibacterial effect of Peruvian propolis collected during different seasons on the growth of Streptococcus Mutans

Introduction: Propolis is a gummy, resinous substance made by bees from the buds and exudates of plants. The antibacterial activity of propolis has been widely studied and is known to vary according to its geographical origin, the type of surrounding flora, the collecting bee species, the mode of its collection and even the season in which it is collected. Unfortunately, these observations have not been corroborated experimentally. Aim: To compare the antibacterial activities of ethanolic extracts of propolis collected in the summer and autumn on the growth of Streptococcus mutans ATCC 25175. Materials and Methods: Propolis samples were collected in the summer and autumn and labeled “A” or “B” by an individual who was not directly involved in the study. Then, 5% ethanolic extracts of propolis were prepared for each sample. S. mutans was plated onto brain heart infusion agar plates into which wells were formed, and the plates were divided into four groups to test the antibacterial effectiveness of both the extracts and the positive (0.12% chlorhexidine digluconate) and negative (96% ethanol) controls. Results: Inhibition halos of 26.4±2.6 and 18.2±1.8 mm were observed for the autumn and summer propolis extracts, respectively, while those of the negative and positive controls were 0 and 13 mm, respectively. These differences were statistically analyzed using Student’s t-test. Conclusion: The significantly higher growth of S. mutans in the extracts made from propolis collected in autumn than that grown on extracts collected in summer indicates that the season in which propolis is collected does indeed influence its antibacterial activity.