Antibacterial properties of Carum copticum essential oil against Streptococcus mutans and Streptococcus sobrinus isolated from canine dental plaque

Abstract

Dental caries is amongst the most prevalent oral diseases in both humans and dogs. Streptococcus mutans and Streptococcus sobrinus (mutans streptococci) are the major cariogenic bacteria isolated from dental caries. Since these bacteria generally show resistance to common antibiotics, natural products such as plant essential oils could be a good substitute. For this study, we aimed to evaluate the antibacterial activity of Carum copticum essential oil against Streptococcus mutans and Streptococcus sobrinus. Twenty canine dental plaque samples were collected and the presence of S. mutans and S. sobrinus in the samples was confirmed using biochemical, culture and polymerase chain reaction (PCR) assays. The resistance patterns of isolates were determined using a disc diffusion method according to the Clinical Laboratory Standards Institute protocol against the following antimicrobials: chloramphenicol, tetracycline, penicillin, erythromycin, ceftriaxone, cefotaxime, vancomycin and azithromycin. The antibacterial activities of Carum copticum essential oil were based on the disc diffusion method as well on a determination of the minimum inhibitory (MIC₅₀) and minimum bactericidal concentration values. S. mutans and S. sobrinus were isolated in 8 (40%) and 2 (10%), respectively, of plaque samples. Most of these isolates were determined to display multidrug resistance patterns to the eight antibiotics evaluated. Screening of the antibacterial activity of the essential oil indicated that MIC₅₀ and minimum bactericidal concentration values were 20 µg/ml and 80 µg/ml, respectively, and that the zone of inhibition in the disc diffusion method ranged from 2 to 5 mm for serial concentrations of the essential oil. Based on our results, we suggest that Carum copticum essential oil exerts antibacterial effects against Streptococcus mutans and Streptococcus sobrinus and may be a useful treatment for carious lesions with bacterial aetiologies.