Abstract In view of residue problems in the environment and the development of insect resistance to synthetic insecticides like DDT and other chlorinated hydrocarbons, the recent trend is to explore plants to obtain extracts that are safe for non-target animals and do not pose any residue problem but are still able to suppress pest populationsMany studies on plant extracts against mosquito have been conducted around the world, and their larvicidal, pupicidal, adult emergence inhibition and repellent activities have been reported. Materials and Methods: In the present study, the objective was to assess the chemical composition of the essential oil obtained by hydrodistillation of dry leaves from Origanum vulgare by GC-FID and GC/MS analyses. The essential oil was tested at different concentrations ranging between 6.25 and 50 ppm on newly molted fourth-instar larvae of Culex pipiens, most abundant mosquito species in Tebessa area (East-Algeria) under standard laboratory conditions according to the World Health Organization recommendations. Results: The essential oil yield calculated from the dry matter of the aerial part of the plant was 1.71 %. The GC-MS analyzes revealed twenty-five compounds in essential oil of O. vulgare. The major chemical components identified was carvacrol (77.63%) (Phenolic monoterpene), followed by γ-terpinene (6.79%) and cymene (5.41%), respectively. Bioassay test revealed that this essential oil was found to exhibit a larvicidal activity with dose-response relationship. Conclusion: The relationship between the chemical composition and biological activity of essential oil of O. vulgare is confirmed by the above-mentioned results. Therefore, the potential for exploiting this essential oil, such as bioinsecticide for vector control, can be taken in to account.
Abstract Development of non-antibiotic alternatives to treat infections caused by multidrug-resistant (MDR) microbes represents one of the top priorities in healthcare and community settings, especially in the care of combat trauma-associated wound infections. Here, we investigate efficacy of oregano oil against pathogenic bacteria including MDR isolates from the combat casualties in vitro and in a mouse burn model. Oregano oil showed a significant anti-bacterial activity against 11 MDR clinical isolates including four Acinetobacter baumannii, three Pseudomonas aeruginosa, and four methicillin-resistant Staphylococcus aureus (MRSA) obtained from combat casualties and two luminescent strains of PA01 and MRSA USA300, with a MIC ranging from 0.08 mg/ml to 0.64 mg/ml. Oregano oil also effectively eradicated biofilms formed by each of the 13 pathogens above at similar MICs. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) revealed that oregano oil damaged bacterial cells and altered the morphology of their biofilms. While efficiently inactivating bacteria, there was no evidence of resistance development after up to 20 consecutive passages of representative bacterial strains in the presence of sublethal doses of oregano oil. In vivo study using the third-degree burn wounds infected with PA01 or USA300 demonstrated that oregano oil, topically applied 24 h after bacterial inoculation, sufficiently reduced the bacterial load in the wounds by 3 log10 in 1 h, as measured by drastic reduction of bacterial bioluminescence. This bactericidal activity of oregano oil concurred with no significant side effect on the skin histologically or genotoxicity after three topical applications of oregano oil at 10 mg/ml for three consecutive days. The investigation suggests potentials of oregano oil as an alternative to antibiotics for the treatment of wound-associated infections regardless of antibiotic susceptibility.
Oil from the common herb oregano may be an effective treatment against dangerous, and sometimes drug-resistant bacteria, a Georgetown researcher has found. Two studies have shown that oregano oil--and, in particular, carvacrol, one of oregano's chemical components--appear to reduce infection as effectively as traditional antibiotics.
