Antibacterial and antibiofilm potential of carvacrol against oral Streptococcus spp. isolates

Abstract

<p>Dental caries is one of the most prevalent public health problems. It is caused by a well-organized bacterial structure <em>i.e.</em>, biofilm, where the cariogenic bacteria <em>Streptococcus mutans</em> is recognized as the primary pathogenic factor. Furthermore, the first phase of dental biofilm onset is predominantly associated to bacteria of the <em>Streptococcus</em> genus. This research aimed to assess the antibacterial and antibiofilm potential of monoterpene carvacrol, against relevant tooth caries-associated isolates, including <em>Streptococcus mutans</em>, <em>Streptococcus sanguinis</em>,<em> Streptococcus mitis</em>, and <em>Streptococcus gordonii</em>. Microdilution test was used for the assessment of the antimicrobial potential of carvacrol, and the minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) were determined. The capacity of carvacrol to disrupt pre-formed biofilm and prevent its formation was evaluated in crystal violet assay. Tested monoterpene achieved notable antimicrobial activity, with MICs ranging from 1.22 mg mL<sup>-1</sup> to 2.44 mg mL<sup>-1</sup>, and MBCs from 1.22 mg mL<sup>-1</sup> to 19.52 mg mL<sup>-1</sup>. Screening of the prevention of biofilm biomass formation revealed that carvacrol has the potential to prevent biofilm formation of the <em>S. sanguinis</em>, <em>S. gordoni</em>i (41% and 47% of inhibition, at concentration 4.88 mg mL<sup>-1</sup> respectively) and <em>S. mutans</em> (at higher tested concentrations 59% of inhibition, at concentration of 19.52 mg mL<sup>-1</sup>). Biofilm disruption also occurred in case of <em>S. mitis</em> and <em>S. sanguinis </em>biofilms (40% and 46% of biomass decrease, respectively, at concentration of 2.44 mg mL<sup>-1</sup>). According to the study results, carvacrol could be valuable as an active antibacterial agent and incorporated in adjunct to oral hygiene maintenance.</p>