Synergism of Gentamicin and Norfloxacin with the Volatile Compounds of Lippia microphylla Cham. (Verbenaceae)

This is the first report of antibiotic modifying activity by the volatile compounds from essential oils of Lippia microphylla Cham. (Verbenaceae). The leaves of Lippia microphylla Cham. (Verbenaceae) were extracted by hydrodistillation, and the essential oil obtained was examined with respect to its effects on the antibiotic activity of gentamicin, tetracycline and norfloxacin by minimal inhibitory dose method and gaseous contact. The gaseous component of the oil inhibited the bacterial growth of the strains of Staphylococcus aureus with a MID of 0.5 mg/L air. The activity of gentamicin against Pseudomonas aerugionosa and norfloxacin against Staphylococcus aureus 1199B was increased by 47% and 225%, whereas no effect or an increased resistance to tetracycline was observed with an inhibition zone 14.3% smaller after contact with the gaseous component of the essential oil. These results show that the volatile compounds of this oil can enhance antibiotic activity, which may lead to the development o...