Antimicrobial activity of Melaleuca sp. oil against clinical isolates of antibiotics resistant Staphylococcus aureus.

PURPOSE To extract the Melaleuca sp. oil and to assess its in vitro inhibitory effect against Staphylococcus aureus isolates obtained from lower limb wounds and resistant to several antibiotics. METHODS A total of 14 test-tubes containing Mueller-Hinton broth were used to determine the Minimum Inhibitory Concentration (MIC). The following concentrations of the Melaleuca sp. oil were added to the first 11 tubes: 8; 4; 2; 1; 0.5; 0.2; 0.1; 0.05; 0.025; 0,0125 and 0.00625%. The 12th and 13th tubes, with and without oil, were used as the positive and negative controls, respectively. The experimental study was carried out in triplicate at 37ºC for 18 hours. The Minimum Bactericidal Concentration (MBC), able of killing all the microorganisms, was also determined. Two S. aureus isolates were obtained from lower limb wounds of female patients and the identification of the microorganisms (Staphylococcus aureus) and the test for susceptibility to the antimicrobial agents were carried out by automation using the apparatus MicroScan(r). After identification, the isolates were preserved in liquid Trypticase Soy medium, and inoculated for determination of the MIC and MBC. RESULTS The MIC was 0.2% and the MBC was 0.4%. CONCLUSION The Melaleuca sp. oil showed antimicrobial properties in vitro against strains isolated from lower limb wounds which were resistant to multiple antibiotics.