Antimicrobial Activity of Carvacrol against Lactobacillus acidophilus and Lactobacillus casei, An In-Vitro Study

Background & Aims: Lactobacillus acidophilus (L. acidophilus) and Lactobacillus casei L. casei) are the primary bacterial
pathogens involved in dental caries and periodontal diseases. In this study, we aimed to investigate the antimicrobial activity of
Carvacrol in inhibiting the growth of these two microbial species in-vitro.
Materials & Methods: In this study, we prepared standard colonies of L. acidophilus and L. casei, then evaluated disk diffusion and
well diffusion tests on De Man-Rugose and Sharpe (MRS) agar plates to determine the antimicrobial activity of Carvacrol. We used
30 μg tetracycline disks as control. To evaluate the minimum inhibitory concentration (MIC), Carvacrol was used in the range of 20
to 0.039 μL in MRS broth medium containing bacteria. To determine the Minimum Bactericidal Concentration (MBC), the contents
of tubes were subsequently cultured on MRS agar plates.
Results: The MIC and MBC of Carvacrol against L. casei were 0.406 ± 0.143 and 0.813 ± 0.287 μg/mL, and against L. acidophilus
were 0.254 ± 0.072 and 0.406 ± 0.143 μg/mL, respectively. In the disk diffusion test, carvacrol solution (2%) significantly induced
inhibitory zones against L. casei and L. acidophilus. Although In the well diffusion test, 2% carvacrol solution generated inhibitory
zones against L. casei. and against L. acidophilus with detectableinhibitory zones, but they werer not statistically significant.. We
noted a significant difference only for the volume of 80 μL of solution (p = 0.03).
Conclusion: The present study indicated that Carvacrol could be used as a natural alternative agent against L. acidophilus and L.
casei generated dental caries.