Antimicrobial activities of the volatile oils of Ocimum bacilicum L. and Ocimum gratissimum L. (Lamiaceae) against some aerobic dental isolates

Essential or volatile oils of plants have been variously reported to have many medicinal applications. Their probable uses against oral microbes have received little attention. Oral swabs obtained from eighteen dental patients at the University of Benin teaching Hospital, Benin City, Nigeria, led to the isolation of twenty nine bacteria. Using standard methods, the microorganisms were identified as Streptococcus viridians (16; representing 55.17%), Staphylococcus albus (9; 31.04%), Klebisiella pneumonia (2; 6.90%), Pseudomonas aeruginosa (1, 3.45%) and Proteus vulgaris (1, 3.45%). The antimicrobial activities of the volatile oils of Ocimum basilicum L. and O. gratissimum L. were evaluated on the twenty nine organisms using agar diffusion and agar dilution methods. In the susceptibility tests, the volatile oils of O. basilicum and O. gratissimum independently inhibited the growth of Klebisiella pneumonia at a concentration of 0.51% in the agar; Streptococcus viridians and Staphylococcus albus at 1.10% and Pseudomonas aeruginosa at 10.0%. Proteus vulgaris was inhibited at 0.53% by the volatile oil of O. gratissimum and 0.67% by O. basilicum. Separate incorporation of the volatile oils into tooth pastes (2 and 5%), the volatiles oils showed antibacterial activities comparable to a commercial tooth paste (which contains O. basilicum 0.01% among others) against most resistant organisms. As components of mouth washes, the volatile oils completely inhibited the growth of organisms at a concentration of 0.5%.