Introduction he use of plants as an alternative to medicinal treatments is an ancient practice, which provide primary health care to 80% of the world's population. It has also been an important source for new drug discoveries (Wangchuk & Tobgay, 2015). World Health Organization has estimated that around 80% of the population of developing countries use traditional herbal medicines as a source of treatment for diseases as a cheap and alternative source, other factors such as the lack of modern health facilities, Cultural priorities and choices also contribute to the use of medicinal plants as a therapeutic alternative (Aziz et al., 2018). Studies on medicinal plants have became increasingly relevant, ethnobotanical and ethnopharmacological knowledge is considered essential for the development of new drugs. Researches studies the effectiveness and use of traditional plants as alternative medicine and adjuvants in a treatment (Amjad et al., 2017). In this context, Origanum vulgare is a plantused since ancient times as a traditional cure for treating infections (Karaman et al., 2017). Studies show that O. vulgare essential oil is rich in Carvacrol, has anti-inflammatory, antioxidant, antispasmodic, antimicrobial, and antifungal activity (Król et al., 2019). Also, resistant microorganisms have emerged over the years and have been considered a global health threat. Microbial resistance has brought problems in the treatment of infectious diseases, and the development of new antimicrobial agents is required (Ayaz et al., 2019). The occurrence that strains of the genus Candida have been resistant to treatment with commercial antifungals, belonging to the azoles and polyenes family, has been a reason for concern by health professionals. Candida infections mainly affect immunosuppressed patients (Barbosa et al., 2019). Given this scenario, the plants are promising antimicrobial agent for the development of new drugs, acting in disease prevention and treatment (Ayaz et al., 2019). Therefore, this work aimed to study the antimicrobial activity of Origanum vulgare essential oil and its isolated compound Carvacrol against microorganisms of genus Candida, Streptococci and, Staphylococci. # II. # Material and Methods # a) Essential oil The essential oil was purchased commercially from Quinarí Fragrâncias e Cosméticos LTDA and the isolated compound from Sigma Aldrich. Essential Oil -Lot: 09818DIV Isolated Compound -Lot: S40656V Origanum vulgare (Oregano) and its Carvacrol Biocomponent as an Alternative of Antimicrobial Agent range of 0.08 to 0.1 equivalent to 5.0 x 10 6 CFU/mL. Then, the inoculum was standardized, diluting to 2.5x 10 3 , according to CLSI, 2008. In asterile microplate was deposited with 100 µl of RPMI, 100 µl of the essential oil or 100 µl of the isolated compound at the initial concentration, followed by serial microdilution and then added with 100 µl of the adjusted inoculum. Groups of test: CG: positive control group; OL: Essential Oil Treatment Group; IC: Treatment group with isolated compound; AC: Treatment group with the commercial antifungal Fluconazole at an initial concentration of 64ug/mL (CLSI, 2002). Incubated the plates for 48h at 37°C. Defined the MIC as the lowest concentration of compound that did not exhibit visible growth of the microorganism. # d) Inoculum adjustment of the Streptococcus spp. and Staphylococcus aureus MRSA After growth in BHI liquid culture medium, the inoculum was adjusted by spectrophotometer with a wavelength of 625nm in the range 0.08 to 0.1absorbance, equivalent to 1.0 x 10 8 CFU/mL. In a sterile microplate were deposited 100 µl of BHI, 100 µl of the essential oil or 100 µl of the isolated compound at the initial concentration, followed by serial microdilution, and then added of 100µl of the adjusted inoculum. Groups of test: CG: positive control group; OL: Essential Oil Treatment Group; IC: Treatment group with isolated compound; AC: Treatment group with the commercial antifungal chlorhexidine at the initial concentration of 64ug/mL (CLSI, 2008). Incubation of the plates was made for 24h at 37°C with 10% CO 2 for Streptococcus strains and aerobically for Staphylococcus aureus MRSA. Defined the MIC as the lowest concentration of compound that did not exhibit visible growth of the microorganism. # e) Determination of Minimum Fungicidal Concentration (CFM) and Minimum Bactericidal Concentration (CBM) In a petri dish containing Sabouraud Dextrose Agar (SDA) for yeast and Brain Heart Infusion Agar (BHI) for bacteria tested the determination of minimum fungicidal concentration (MFC) and minimum bactericidal concentration (MBC). Homogeinized the wells containing target concentrations and transferred the aliquot to the Petri dish with the solid culture medium. After incubation at 37ºC for 24h, established the lowest fungicidal/bactericidal concentration. Determined the MFC/MBC as the lowest concentration of essential oils and isolated compounds that did not allow the growth of any colony of the microorganism on the solid medium after the incubation period. Through visual reading, the inhibition of growth or death provided by the tested substances was confirmed (GULLO et al., 2012). # III. # Results # a) Evaluation of Minimum Inhibitory Concentration (MIC) and Minimum Fungicidal / Bactericidal Concentration (CFM / CBM) Tested the Origanum vulgare essential oil and its isolated compound Carvacrol against reference strains of the genus Candida, Streptococcus, and Staphylococcus aureus methicillin-resistant strain to determine its inhibitory effect by broth microdilution technique. Both substances showed inhibitory activity on microbial cells (Table 1).For reference strains of the genus Candida, inhibitory concentrations were between 0.125 mg/mL and 0.5 mg/mL for O. vulgare essential oil and 0.125 mg/mL and 0.0625 mg/mL for Carvacrol isolated compound. The antifungal Fluconazole was also tested against strains to determine the minimum inhibitory concentration by broth microdilution technique. Fluconazole has shown inhibitory activity between 1 and 32 µg/ml (Table 1). For bacterial strains of the genus Streptococcus, the essential oil of O. vulgare behaved similarly, varying the MIC between concentrations of 0.5 mg/mL and 0.250 mg/mL, as well as its isolated compound Carvacrol. The essential oil and Carvacrol inhibited the strain Staphylococcus aureus at concentrations of 0.5 and 0.250 mg/mL respectively. Chlorhexidine antimicrobial was also tested against strains to determine the minimum inhibitory concentration by broth microdilution technique. Chlorhexidine demonstrated inhibitory activity between 3.75 to 7 µg/ml (Table 1).After the determined the MIC values, used an aliquot of the susceptibility test to determine the minimum fungicidal/bactericidal concentration (MFC/MBC) of the strains. For Candida spp. Strains, O. vulgare essential oil, showed fungicidal activity against Candida spp. strains, varying its effect on concentrations between 0.5 mg/mL and 0.250 mg/mL; while Carvacrol showed 0.250 mg/mL fungicidal activity for all Candida strains tested (Table 1). Streptococcus bacterial strains showed a bactericidal concentration ranging from 0.5 mg/mL to 0.250 mg/mL for the essential oil and ranged from 0.5 mg/mL to 0.125 mg/mL for the isolated compound. S. aureus(MRSA) showed a bactericidal concentration of 0.5 mg/mL for both. Table 1: Visual reading results of MIC and CFM/CBM of the strains tested. # IV. # Discussion Excessive and indiscriminate use of antimicrobials is a major determinant of some emerging infections, selection of resistant pathogens, and the continued development of antimicrobial resistance globally. The increasing emergence of multi-drug resistant organisms and the limited development of new agents available to combat them have caused an imminent crisis with alarming implications (Sartelli et al., 2016).In view of the increasing numbers of cases of conventional drug-resistant microorganisms, researchers are looking for alternatives to biocompounds that have antimicrobial properties against microorganisms. Studies with plants as promising agents in the search for new compounds. In this study, the obtained data showed antimicrobial activity of the tested essential oil, as well as its isolated compound against planktonic cells of Candida spp., oral Streptococcus species, and S. aureus methicillin resistant strain. The essential oil inhibited antimicrobial growth between concentrations of 0.5 to 0.125mg/mL against all strains tested. At the same time, the isolated compound showed antimicrobial activity between concentrations of 0.250 to 0.0625mg/mL against all strains tested. The minimum fungicidal/bactericidal concentration (MFC/MBC) of the essential oil in the strains tested was between 0.5 mg / ml and 0.250 mg / ml. The isolated compound showed MFC/MBC between concentrations of0.5 mg/mL to 0.125 mg/mL (Table 1). These data, initially reveal the antimicrobial action of this essential oil, as well as its isolated compound, corroborating with the literature, pointing out # Reference strain # O. vulgare Carvacrol The data obtained in this study added to the data in the recent literature, suggest that the essential oil of O. vulgare and also its isolated compound Carvacrol show antibacterial and antifungal potential. These data open possibilities for many other studies, such as the performance of these oils and biocomponents in mature biofilms and multispecies biofilms, evaluating cell viability and possible morphological changes, added to cytotoxicity tests, action on cancer cells, in an attempt to add more information about this plant and its use as an alternative agent in the treatment of infections and acting as coadjuvants. V. # Conclusion ? Both the essential oil of O. vulgare, and its isolated compound Carvacrol, can inhibit the growth of the tested microorganisms in low concentrations; ? The isolated compound is more effective when compared to the essential oil, inhibiting the microorganisms in a lower concentration; ? About the microorganisms, essential oil and Carvacrol are more effective against Candida spp. when compared to bacterial strains; ? Both the EO and its main biocomponent Carvacrol show fungicidal/bactericidal activity against the tested strains * Descriptive study of plant resources in the context of the ethnomedicinal relevance of indigenous flora: A case study from Toli Peer National Park MSAmjad MFQaeem IAhmad SUKhan SKChaudhari NZMalik HShaheen AMKhan 2017 12 e0171896 Azad Jammu and Kashmir, Pakistan. PLoSOne * Synergistic interactions of phytochemicals with antimicrobial agents: Potential strategy to counteract drug resistance. ChemBiol Interact MAyaz FUllah ASadiq FUllah MOvais AhmedJ Devkotahp 2019 May 31 308 * Traditional uses of medicinal plants practiced by the indigenous communities at Mohmand Agency, FATA, Pakistan MAAziz AdnanMKhan AHShahat AAAl-Said MSUllah R J Ethnobiol Ethnomed 14 2 2018 * Anti-Candida Activity of Essential Oils from Eucalyptus species. A Preliminary Study JPBarbosa TROliveira DgpbPuppin ALTeixeira GCBoni SnbFeiria JFHöfling Adv Dent & Oral Health 8 3 2018 * Antibacterial activities of Origanum vulgare alone and in combination with different antimicrobials against clinical isolates of Salmonella typhi. AncSci Life VBarthi NVasudeva SSharma JSDuhan 2013 Apr-Jun 32 * Characterization of Herbal Antifungal Agent, Origanum vulgare against Oral Candida spp. Isolated from Patients with Candida-Associated Denture Stomatitis: An In vitro Study VBhat SMSharma VShetty CSShastry VamanRao CShenoy SSaha SBalaji S Contemp Clin Dent 9 2018 jun * In vitro activity of Origanum vulgare essential oil against Candida species MBCleff ARMeinerz MXavier LSchuch Brazilian Journal of Microbiology 41 1 2010 * Método de referência para testes de diluição em caldo para a determinação da sensibilidade de leveduras a terapia antifúngica. Clinicaland laboratorial standards institute Clsi 2008. 2008 CLSI Norma M27-A3, v.28, n.14, 2 ed. * Anti-Candida activity of Brazilian medicinal plants MCDuarte GMFigueira SartorattoUm VLRehder CDelarmelina J Ethnopharmacol 97 2 2005 * Antifungal activity of Maytenin and Pristimerin FPGullo JcoSardi VaffmSantos FSangalli-Leite NSPitangui SARossi PaulaDe AcaSilva 2012 Hindawi Publishing Corporation * MKaraman MBogavac BRadovanovi? JSudji KTesanovic LJanjusevic * Origanumvulgare essential oil affects pathogens causing vaginal infections Journal of Applied Microbiology 122 2017 * Investigation of the antifungal activity of carvacrol against strains of Cryptococcus neoformans BKról BKolodziej BKedzia EHolderna-Kedzia DSugier KLuchowska RONóbrega APTeixeira WAOliveira EOLima IOLima J Sci Food Agric 13 11 2019. 2016 Nov Pharm Biol * Antimicrobials: a global alliance for optimizing their rational use in intra-abdominal infections MSartelli World J EmergSurg 11 33 2016 * Membrane Destruction and DNA Binding of Staphylococcus aureus Cells Induced by Carvacrol and Its Combined Effect with a Pulsed Electric Field LHWang MSWang XAZeng ZHZhang DMGong YBHuang J AgricFoodChem 64 32 2016 Aug 17 * Contributions of medicinal plants to the Gross National Happiness and Biodiscovery in Bhutan PWangchuk TTobgay J Ethnobiol Ethnomed 11 48 2015