In vitro antimicrobial activity of mouth washes and herbal products against dental biofilm-forming bacteria

Aim: To evaluate in vitro, the antimicrobial effect of Cymbopogon citrates (lemon grass), Plectranthusamboinicus (Mexican mint) and Conyzabonariensis (hairy fleabane) tinctures as well as pure and diluted commercial mouth washes (Malvatricin(®), Periogard(®) and Listerine(®)) on wild isolates of Streptococcusmutans and reference strains of S. mutans, Streptococcus salivarius, Streptococcus oralis and Lactobacillus casei by determination of minimum inhibitory dilution (MID).

Materials and methods: 0.12% chlorhexidine and 70% corn alcohol were used as positive and negative controls, respectively. Saliva samples were collected from 3 volunteers and seeded in MSB broth to obtain Streptococcus isolates after 72-hour incubation. Using the agar diffusion method, susceptibility tests were performed with overnight incubation in microaerophilia at 37°C. All tests were performed in duplicate.

Results: The bacterial species were resistant to the tinctures and Listerine(®), but were susceptible to 0.12% chlorhexidine, Malvatricin(®) and Periogard(®), with MIDs ranging from 12.5% to 1.56%.

Conclusions: Plectrantusamboinicus, Conyzabonariensis and Cymbopongoncitratus tinctures and Listerine(®) did not show inhibitory action against the tested biofilm-forming bacteria.