Global Advanced Research Journal of Microbiology::::::GARJM>Khatib et al: Study on Antibacterial effect of some Lebanese plant oils against some multi drug-resistant bacteria.

Background: to evaluate the antibacterial effect of some plant oils on the growth of certain Gram negative multi-drug resistant bacteria namely: five different strains of E.coli and pseudomonas aeuroginosa. Methods: Antibacterial activity was carried out using a disc-diffusion method, The MIC of the active essential oils were tested using two fold dilution method, the minimal bactericidal concentration (MBC) was then recorded. A time kill curve was assessed to investigate the best time for oil to kill the bacterial vegetative cells, The bacteria under test were treated with the most promising oil that showed bactericidal or bacteriostatic effect and then Electron Micrographs were taken using a Transmission electron microscope (JEM-100 CX Joel), at the Electron Microscope Unit, Faculty of Science, Alexandria University. Results: Five out of ten oils tested (Pine ,Sage,Lavander,Menth and Thyme oils ) showed antibacterial activity against the growth of some Gram negative multi-drug resistant bacteria under test. Pine oil showed a significant inhibitory effect against E.coli , whereas, menth oil showed a significant inhibitory effect on the growth of Pseudomonas aeuroginosa (at P ≤ 0.05).Concerning the minimal bactericidal concentration, all essential oils used in the present investigation had bacteriostatic effect against the multi drug resistant bacteria under test except pine oil was showed a bactericidal effect against ESBL-E.coli A with MBC value (500µl/ml). Pine essential oil showed bactericidal activity (no viable cells detected) against the multi-drug resistant bacterium within 12 hrs.TEM showed bacterial cell lyses and leakage of cytoplasmic materials when treated by bactericidal essential oil, while bacteriostatic essential oil cause shrinkage in bacterial cell wall, cell metamorphoses and increasing cytoplasm turbidity with oil accumulation inside the cell. Conclusion: It was concluded that pine, peppermint, sage, lavender and thyme oils may be potential sources of new and selective agents for the treatment of urinary tract infection. Further studies on their cytotoxic effect will be beneficial in providing data on the possible harmfull effects of the previously mentioned promising oils. An additional investigation for the irritant effects is also required to be used as a topical medical agent.

Keywords: Antibacterial effect, Lebanese plant oil, multi drug-resistant bacteria.