Mutans Streptococci are significant pathogens isolated from dental plaques. Due to the increasing frequency of antimicrobial resistance among pathogens causing dental caries, more studies have focused on using natural agents against them. This study aimed to evaluate the antibacterial effects of Trachyspermum ammi essential oil against Streptococcus mutans isolated from dental plaques.

Twenty human dental plaque samples were collected, and eight S. mutans isolates were detected using biochemical and molecular tests. The antibiotic susceptibility patterns of the isolates were determined by the disc diffusion method. Also, T. ammi essential oil antibacterial activity was investigated using the disc diffusion method and determining minimum inhibitory concentration (MIC50) and minimum bactericidal concentration (MBC) values.

Phenotypic and genotypic characterization identified S. mutans in 40% of the samples. The antibiotic susceptibility assay revealed the highest resistance patterns against cefotaxime (100%), ceftriaxone (100%), and penicillin (87.5%). The T. ammi essential oil demonstrated 20 µg/ml MIC and 80µg/ml MBC against S. mutans.

The present study revealed a potent antibacterial activity for T. ammi essential oil against S. mutans isolates.