A comparative study on the antimicrobial properties of extracts from medicinal plants obtained by two di¡erent methods was carried out.The screening of the antimicrobial activity of extracts from six plants was conducted by a disc di¡usion test against Gram-positive, -negative and fungal organisms.The most active extracts (inhibition diameter r12 mm) were assayed for the minimum inhibitory concentration and submitted to phytochemical screening by thin-layer chromatography and bioautography.The results obtained indicate that the diethyl ether extracts were the most e¤cient antimicrobial compounds.The activity was more pronounced against Gram-positive and fungal organisms than against Gram-negative bacteria. Bioautography showed that the antimicrobial activity was probably due to £avonoids and terpenes.

The aim of this study was to evaluate the effect of oregano essential oil, carvacrol and thymol on biofilm-grown Staphylococcus aureus and Staphylococcus epidermidis strains, as well as the effects of the oils on biofilm formation. For most of the S. aureus (n56) and S. epidermidis (n56) strains tested, the biofilm inhibitory concentration (0.125-0.500 %, v/v, for oregano, and 0.031-0.125 %, v/v, for carvacrol and thymol) and biofilm eradication concentration (0.25-1.0 %, v/v, for oregano and 0.125-0.500 %, v/v, for carvacrol and thymol) values were twofold or fourfold greater than the concentration required to inhibit planktonic growth. Subinhibitory concentrations of the oils attenuated biofilm formation of S. aureus and S. epidermidis strains on polystyrene microtitre plates. INTRODUCTIONStaphylococci are important nosocomial pathogens. Eradication of these micro-organisms is not always successful due to their ability to form biofilms. Experimental evidence has shown that micro-organisms in biofilms are less susceptible to conventional treatment (Brown & Gilbert, 1993) than their planktonic counterparts. Many factors contribute to the lowered susceptibility of bacteria enclosed in a biofilm, and include the induction of a biofilm phenotype, the stress response and failure of the antimicrobial agents to penetrate the biofilm (Mah & O'Toole, 2001).As such, alternative strategies or more effective agents exhibiting activity against biofilm-producing micro-organisms are of great interest. Natural drugs could represent an interesting approach to limit the emergence and the spread of these organisms, which currently are difficult to treat. Recently, there has been considerable interest in the study of plant materials as sources of new compounds for processing into therapeutic agents. One approach may be the use of essential oils that have been shown to be potential agents in the treatment of infections, and are safe in terms of human and animal health. In this context, oregano oil and its major phenolic components, carvacrol [2-methyl-5-(1-methylethyl)phenol] and thymol (2-isopropyl-5-methylphenol), are known for their wide spectrum of antimicrobial activity, which has been the subject of several investigations in vitro (Dorman & Deans, 2000;Lambert et al., 2001) and in vivo (Adam et al., 1998;Manohar et al., 2001). They possess multiple biological properties such as anti-inflammatory, anti-leishmanial, antioxidant, hepatoprotective and anti-tumoral activities (Aeschbach et al., 1994; Alam et al., 1999; Robledo et al., 2005;Skold et al., 1998;Weber & de Bont, 1996;Zeytinoglu et al., 2003).Previously, we have shown the efficacy of oregano oil, carvacrol and thymol against planktonic Staphylococcus aureus and Staphylococcus epidermidis, including meticillinresistant strains (Nostro et al., 2004). The objective of this study was to extend the research to evaluate the activity of oregano oil, carvacrol and thymol on biofilm-grown S. aureus and S. epidermidis strains, as well as the effects of oils on biofilm formation....

The aim of this study was to evaluate the susceptibility of methicillin-susceptible and methicillin-resistant staphylococci (MSS, MRS) to oregano essential oil, carvacrol and thymol. The commercial aerial parts of Origanum vulgare L. were hydrodistilled and the essential oil analysed by gas- chromatography/electron impact mass spectrometry. The inhibition efficacy of this essence and its major components was assayed against 26 MSS and 21 MRS, using an agar dilution method. The methicillin resistance was thoroughly typed by Epsilometer test (E-test), polymerase chain reaction for mecA gene detection and PBP2' latex agglutination test. The results clearly demonstrated that the comparison between the susceptibility of MSS and MRS to oregano oil, carvacrol and thymol showed no significant differences (Fisher's exact test, P > 0.05). The best minimum inhibitory concentration values were reported for carvacrol (0.015-0.03%, v/v) followed by thymol (0.03-0.06%, v/v) and oregano oil (0.06-0.125%, v/v).

Aims:  The in vitro activity of some essential oils (EO) (thyme red, fennel, clove, pine, sage, lemon balm and lavender) against clinical and environmental fungal strains was determined. Methods and Results:  The minimal inhibitory concentrations were determined by a microdilution method in RPMI 1640 and by a vapour contact assay. The composition of oils was analysed by gas chromatography (GC) and GC/mass spectrometry. The results indicated that the oils antifungal activity depended on the experimental assay used. The inhibiting effects of EO in vapour phase were generally higher than those in liquid state. According to both methods thyme red and clove were found to be the oils with the widest spectrum of activity against all fungi tested. Conclusions:  Despite the differences between the two methods, our results demonstrate that some EO are very active on dermatophytes and dematiaceous fungi. However, more data will be necessary to confirm this good in vitro efficacy. Significance and Impact of the Study:  This study could identify candidates of EO for developing alternative methods to control environmental and clinically undesirable filamentous fungi.

Polyethylene-co-vinylacetate (EVA) films with different concentrations (3.5 wt% and 7 wt%) of essential oil constituents, carvacrol or cinnamaldehyde, were prepared and characterized by mechanical, antibacterial and antibiofilm properties. The incorporation of the compounds into copolymer films affected their elastic modulus, tensile stress and elongation at break. Carvacrol and cinnamaldehyde act as plasticizers which reduce the intermolecular forces of polymer chains, thus improving the flexibility and extensibility of the film. The analysis of the surface characteristics demonstrated that essential oil constituents lowered the contact angle values without causing any remarkable variation of the surface roughness. The films allowed progressive diffusion of the bioactive molecules and the kinetic of release was correlated with the damaging effect on bacterial growth. The kill curves proved that the film with essential oil constituents (7 wt%) had a significant bactericidal effect (reduction of 4 and 2 log CFU) against Staphylococcus aureus and Escherichia coli and a bacteriostatic effect against Staphylococcus epidermidis and Listeria monocytogenes (reduction of about 1 log CFU). With regard to biofilm formation the biomass formed on polymeric films surface was significantly reduced if compared with the pure copolymer control. The results were confirmed by fluorescence microscopy images by Live/dead staining. The reduction in the surface tension coupled to an inherent bactericidal property of carvacrol and cinnamaldehyde could in turn affect the initial attachment phase of bacteria and compromise the normal biofilm development.