In vitro antibacterial activity of some plant essential oils.
BACKGROUND
To evaluate the antibacterial activity of 21 plant essential oils against six bacterial species.


METHODS
The selected essential oils were screened against four gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus vulgaris) and two gram-positive bacteria Bacillus subtilis and Staphylococcus aureus at four different concentrations (1:1, 1:5, 1:10 and 1:20) using disc diffusion method. The MIC of the active essential oils were tested using two fold agar dilution method at concentrations ranging from 0.2 to 25.6 mg/ml.


RESULTS
Out of 21 essential oils tested, 19 oils showed antibacterial activity against one or more strains. Cinnamon, clove, geranium, lemon, lime, orange and rosemary oils exhibited significant inhibitory effect. Cinnamon oil showed promising inhibitory activity even at low concentration, whereas aniseed, eucalyptus and camphor oils were least active against the tested bacteria. In general, B. subtilis was the most susceptible. On the other hand, K. pneumoniae exhibited low degree of sensitivity.


CONCLUSIONS
Majority of the oils showed antibacterial activity against the tested strains. However Cinnamon, clove and lime oils were found to be inhibiting both gram-positive and gram-negative bacteria. Cinnamon oil can be a good source of antibacterial agents.
Prabuseenivasan
Seenivasan
S
Entomology Research Institute, Loyola College, Chennai--600 034, India. prabsri@gmail.com
Jayakumar
Manickkam
M
Ignacimuthu
Savarimuthu
S
D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D001412:Bacillus subtilis / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects; D066298:In Vitro Techniques; D007711:Klebsiella pneumoniae / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D009822:Oils, Volatile / Q000737:chemistry / Q000494:pharmacology*; D008517:Phytotherapy; D010938:Plant Oils / Q000737:chemistry / Q000494:pharmacology*; D011514:Proteus vulgaris / Q000187:drug effects; D011550:Pseudomonas aeruginosa / Q000187:drug effects; D013211:Staphylococcus aureus / Q000187:drug effects
D000900:Anti-Bacterial Agents; D009822:Oils, Volatile; D010938:Plant Oils