Antimicrobial activity of a novel Spanish propolis against planktonic and sessile oral Streptococcus spp

M Luisa Navarro-Pérez,Ciro Pérez-Giraldo,M Coronada Fernández-Calderón,Virginia Vadillo-Rodríguez,Irene Fernández-Babiano

doi:10.1038/s41598-021-03202-1

Abstract

Increased bacterial resistance to traditional antimicrobial agents has prompted the use of natural products with antimicrobial properties such as propolis, extensively employed since ancient times. However, the chemical composition of propolis extracts is extremely complex and has been shown to vary depending on the region and season of collection, due to variations in the flora from which the pharmacological substances are obtained, being therefore essential for their antimicrobial activity to be checked before use. For this purpose, we evaluate the in vitro antimicrobial and anti-biofilm activity of a new and promising Spanish ethanolic extract of propolis (SEEP) on Streptococcus mutans and Streptococcus sanguinis, responsible, as dominant ‘pioneer’ species, for dental plaque. Results reveal that S. sanguinis is more sensitive to SEEP, slowing and retarding its growth considerably with lower concentrations than those needed to produce the same effect in S. mutans. SEEP presents concentration- and time-dependent killing activity and, furthermore, some of the subinhibitory concentrations employed increased biofilm formation even when bacterial growth decreased. Mono and dual-species biofilms were also inhibited by SEEP. Findings obtained clearly show the relevance of using biofilm and subinhibitory concentration models to determine optimal treatment concentrations.

Highlights

Propolis is a natural complex resinous mixture obtained from beehives, produced by honeybees mixing products collected from tree buds, plants, saps, resins, and other botanical sources, with beeswax and salivary e nzymes[1]
The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values of Spanish ethanolic extract of propolis (SEEP) estimated for S. mutans were 240 μg/mL (0.4%) and 480 μg/mL (0.8%), respectively
The biological activity of SEEP detected was not influenced by the presence of ethanol in the propolis solutions, as a minimum solvent concentration of around 12.5% was required to inhibit the growth of both strains

Summary

Introduction

Propolis is a natural complex resinous mixture obtained from beehives, produced by honeybees mixing products collected from tree buds, plants, saps, resins, and other botanical sources, with beeswax and salivary e nzymes[1]. SEEP shows antibacterial activity against Staphylococcus epidermidis[10] and antifungal activity against Candida glabrata[11]. Based on their excellent biological properties, the use of propolis extract is considered for the prevention and treatment of oral diseases, associated to the accumulation of pathogenic biofilm. The genus Streptococcus represents a high percentage of all supragingival microorganisms present in the oral biofilm. In this sense, S. mutans is one of the most common members of the Mutans group and plays an important role in the etiology of human dental caries and Centre on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Badajoz, Spain. As a pioneering colonizer, S. sanguinis may enable attachment of succeeding pathogens facilitating biofilm formation[16]

Methods

Results

Conclusion