Antibacterial and antifungal activity of ten essential oils in vitro

The essential oils of aegle, ageratum, citronella, eucalyptus, geranium, lemongrass, orange, palmarosa, patchouli and peppermint, were tested for antibacterial activity against 22 bacteria, including Gram-positive cocci and rods and Gram-negative rods, and twelve fungi (3 yeast-like and 9 filamentous) by the disc diffusion method. Lemongrass, eucalyptus, peppermint and orange oils were effective against all the 22 bacterial strains. Aegle and palmarosa oils inhibited 21 bacteria; patchouli and ageratum oils inhibited 20 bacteria and citronella and geranium oils were inhibitory to 15 and 12 bacterial strains, respectively. All twelve fungi were inhibited by seven oils (aegle, citronella, geranium, lemongrass, orange, palmarosa and patchouli). Eucalyptus and peppermint oils were effective against eleven fungi. Ageratum oil was inhibitory to only four fungi tested. The MIC of eucalyptus, lemongrass, palmarosa and peppermint oils ranged from 0.16 to >20 μl ml^-1 for eighteen bacteria and from 0.25 to 10 μl ml^-1 for twelve fungi.