Antimicrobial Activity of Oregano, Thyme, and Lavender Oils Against Oral Pathogens: Perspectives for AI-Supported Research

Antibiotics are widely used on dairy farms to treat and prevent diseases such as mastitis, contributing to the growing issue of antimicrobial resistance, which threatens human and animal health. This study evaluated the antibacterial properties of three essential oils from the Lamiaceae family: Rosmarinus officinalis L., Rosmarinus tournefortii de Noé, and Origanum vulgare L. subsp. glandulosum (Desf.) Ietswaart against bovine mastitis-associated bacteria and fungi in northeast Algeria. The chemical composition of the essential oils was analyzed using gas chromatography-mass spectrometry, and the antimicrobial activity was assessed via agar disk diffusion and vapor phase methods by measuring inhibition zones. Quantitative antibacterial and antifungal activities were determined using broth microdilution to calculate minimum inhibitory, bactericidal, and fungicidal concentrations. Principal component analysis (PCA) was used to evaluate the relationship between minimum inhibitory concentration values and essential oils’ component concentrations. Gas chromatography-mass spectrometry analysis identified 68, 70, and 55 compounds in Rosmarinus officinalis L., Rosmarinus tournefortii de Noé, and Origanum vulgare L. subsp. glandulosum (Desf.) Ietswaart, respectively. Major components included 1,8-cineole (38.76%– 42.55%) in Rosmarinus officinalis L. and Rosmarinus tournefortii de Noé, and γ-terpinene (27.11%) and thymol (22.11%) in Origanum vulgare L. subsp. glandulosum (Desf.) Ietswaart. Agar disk diffusion showed that Origanum vulgare L. subsp. glandulosum (Desf.) Ietswaart exhibited strong antibacterial activity, particularly against E. coli ATCC 25922 (IZ=25.41 ± 1.58–63.77 ± 0.72 mm), while Rosmarinus officinalis L. showed moderate activity. In vapor phase tests, Origanum vulgare L. subsp. glandulosum (Desf.) Ietswaart was active against all tested strains except P. aeruginosa. Origanum vulgare L. subsp. glandulosum (Desf.) Ietswaart had the highest efficacy, with minimum bactericidal concentration and minimum fungicidal concentration values ranging from 8–32 mg/mL and 1–4 mg/mL, respectively. The results demonstrated the bacteriostatic and fungistatic properties of the essential oils. The principal component analysis results highlight a clear distinction between the chemical and functional properties of the studied EOs, with some strains being more sensitive and others closely aligning with specific essential oil components, with Origanum vulgare L. subsp. glandulosum (Desf.) Ietswaart standing out as the most potent. These findings highlight the potential of these essential oils, particularly Origanum vulgare L. subsp. glandulosum (Desf.) Ietswaart, as promising biodegradable alternatives to antibiotics for controlling pathogens associated with bovine mastitis, aligning with the One Health approach to address human, animal, and environmental health. Cite this article as: Daïa, M. Elhaddi, Messaï, A., Gherissi, D. Eddine, Rahmani, R., Aydi, S., & Boulebda, N. (2025). Antibacterial activity of northeast algerians’ essential oils of rosmarinus officinalis L., rosmarinus tournefortii de noé, and origanum vulgare L. subsp. glandulosum (desf.) letswaart against major pathogens of bovine mastitis: in vitro evaluation. Acta Veterinaria Eurasia, 2025, 51, 0051, Doi: 10.5152/actavet.2025.25051.

Introduction: In response to concerns arising from the application of synthetic preservatives in foodstuffs, several alternative methods have been proposed, such as the application of natural preservatives. This study aimed to evaluate the potential application of natural-based Lavandula angustifolia essential oil (LEO) as a food preservative by means of in-vitro antimicrobial and antioxidant assays. Methods: The main constituents of LEO were determined by GC-MS method. To assess the antibacterial efficacy of the tested LEO, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the oil were determined against four important foodborne pathogens by microdilution broth method. Finally, DPPH method was used for the evaluation of the antioxidant properties of the LEO. Results: According to the chemical analysis, terpenes, like linalool and 1,8- Cineol, constitute the main part of LEO. Antioxidant evaluation revealed that the DPPH radicals inhibitory percentage of LEO in concentrations of 40, 80, 120, 160, 200 and 240 (I¼g/ml) were 31, 43, 47, 53, 60 and 66 (), respectively. Regarding antibacterial analysis, the tested LEO could efficiently inhibit and kill the microorganisms including Staphylococcus aureus, Escherichia coli, Bacillus cereus, Salmonella typhimorium and Listeria monocytogenes with the MIC and MBC range of 1.5 to 4 mg/ml. Conclusion: In conclusion, this work indicates the promising antimicrobial and antioxidant potential of LEO to be considered by food scientists and researchers in future studies.

Objective: Candida strains have been frequently associated with nosocomial infections in recent years. On the other hand, public prefer natural resources rather than synthetic materials. Therefore, it is important to research combine effects of natural products. This study aimed to investigate the antifungal and antibiofilm effectiveness of essential oils and propolis containing samples on Candida species and the toxicity of samples. Material-Method: Three different samples were prepared with propolis, lavender oil and thyme oil. Gas Chromatography-mass Spectrometry (GC/MS) GC/MS was used for the determination of organic compounds in samples. The antifungal effects of a natural product mix were tested against C. albicans, C. krusei and C. parapsilosis by disk diffusion method. MIC and MFC tests of the mixture were performed against a standard such as Nystatin. Antibiofilm tests were performed with the microplate system, taking into account the detected concentrations. Finally, in the cytotoxicity test investigated in the L929 cell line with the WST-1 kit. Results: C. albicans was determined as the most sensitive species (MIC50: 90 ppm, MIC90: 750 ppm MFC: 3120 ppm). In the antibiofilm tests, it was determined that the sample was more effective on C. albicans and it inhibited biofilm formation. Also it was determined the IC50 value was 5052 ppm. Conclusion: The natural product mixture, which has scientifically proven antifungal effect, has a feature that has high added value and contributes to the economy. But of course, it has to investigate by further studies. The findings of this study may lead to new therapeutic approaches with standardized natural products in the future.

This study was conducted to investigate the impact of thyme (Thymus vulgaris l.) and lavender (Lavandula augustifolia m.) oils supplementation and their combination in broiler's diet on productive performance and some blood parameters. A total number of 120 broiler chicks (Arbor Acres) of one-week old were used in this study. Birds were randomly divided into 4 groups. The birds in each group were distributed to 3 replicates, 10 birds each. The first group (T1) was served as a control group and received only a basal diet. The 2nd group (T2) was fed basal diet supplemented with thyme oil at level of 0.4 ml/ kg diet. The 3th group (T3) was fed basal diet supplemented with lavender oil at level of 0.5 ml/ kg diet and 4th group (T4) was supplemented with mixture of thyme and lavender oils at levels of 0.4 and o.5 ml/kg diet, respectively. Results showed that supplementing thyme oil or mixture of thyme and lavender had no significant effect on live body weight (LBW) at the end of trial, while feed intake was significantly reduced, and feed conversion ratio was significantly improved compared with the control and lavender groups. Also, thyme and mixture group significantly increased thymus and bursa of Fabricius relative weights. Total blood protein, total albumin and total globulin were significantly increased by adding thyme or mixture of oils to broiler diet. Whilst, total cholesterol, triglyceride, LDL were significantly decreased, and HDL was significantly increased by adding thyme oil to broiler diet.

Objectives:This study was aimed to find out the minimum inhibitory concentration (MIC) of five essential oils against oral pathogens and to find out the minimum bactericidal concentration (MBC) and minimum fungicidal concentration (MFC) of five essential oils against oral pathogens.Materials and Methods:The antimicrobial activities by detecting MIC and MBC/MFC of five essential oils such as tea tree oil, lavender oil, thyme oil, peppermint oil and eugenol oil were evaluated against four common oral pathogens by broth dilution method. The strains used for the study were Staphylococcus aureus ATCC 25923, Enterococcus fecalis ATCC 29212, Escherichia coli ATCC 25922 and Candida albicans ATCC 90028.Results:Out of five essential oils, eugenol oil, peppermint oil, tea tree oil exhibited significant inhibitory effect with mean MIC of 0.62 ± 0.45, 9.00 ± 15.34, 17.12 ± 31.25 subsequently. Mean MBC/MFC for tea tree oil was 17.12 ± 31.25, for lavender oil 151.00 ± 241.82, for thyme oil 22.00 ± 12.00, for peppermint oil 9.75 ± 14.88 and for eugenol oil 0.62 ± 0.45. E. fecalis exhibited low degree of sensitivity compared with all essential oils.Conclusion:Peppermint, tea tree and thyme oil can act as an effective intracanal antiseptic solution against oral pathogens.

The effectiveness of plant essential oils on the growth of Botrytis cinerea, Fusarium sp. and Clavibacter michiganensis subsp. michiganensis

The effect of vacuum packaging, EDTA, oregano and thyme oils on the microbiological quality of chicken's breast

The antibacterial activity of essential oils (EOs) from Carum carvi, Cinnamomum zeylanicum, Cuminum cyminum, Eugenia caryophyllus, Foeniculum vulgare, Melaleuca alternifolia, Mentha × piperita, Origanum vulgare, Rosmarinus officinalis and Thymus vulgaris was tested against Pectobacterium carotovorum subsp. carotovorum (Pcc) and Pectobacterium atrosepticum (Pa), which cause soft rot of potato tubers. In disc diffusion, minimum inhibitory concentration and minimum bactericidal concentration (MBC) tests, cinnamon EO was found to be most effective against both bacteria. The inhibition zones ranged from 20.46 to 29.58 mm for a concentration of 100 μL/mL. The minimum inhibitory concentration was 0.5 μL/mL, and MBC was between 0.5 and 5 μL/mL. The higher sensitivity of bacteria was manifested in clove (Pcc and Pa), mint (Pcc), oregano (Pa) and thyme (Pa) EOs. Rosemary EO was the least effective. The results of the in vivo test were not entirely consistent with those of the in vitro tests. The most significant antibacterial effect was achieved with mint EO. The treatment of potato tuber discs with mint EO at a concentration of 3 μL/mL for Pcc and 3–10 μL/mL for Pa was 100% effective. The efficacy of the essential oils of caraway (5–10 μL/mL), thyme (10 μL/mL) and oregano (5 μL/mL) also ranged from 95.7 to 99.7%. Based on the results of the in vivo test, it may be recommended that mint EO and potentially caraway, oregano and thyme EOs be further tested for pickling potato tubers against bacteria of the genus Pectobacterium.

The aim of this study was to determine the activity of common thyme (Thymus vulgare L.), Greek oregano (Origanum vulgare L. ssp. hirtum), and common oregano (Origanum vulgare L. ssp. vulgare) essential oils (EOs) against selected phytopathogenic microorganisms in relation to their chemical profile. The EOs were obtained from the herbs of 2-year-old plants cultivated in the organic farming system in a temperate climate in Central Europe. The EOs' composition was determined by GC/MS and GC/FID. The investigated species were represented by the following three chemotypes: 'thymol' for common thyme, 'carvacrol' for Greek oregano, and mixed 'caryophyllene oxide + β-caryophyllene' for common oregano. The antimicrobial activity of the EOs was assessed based on minimum inhibitory concentration (MIC) and minimum bactericidal/fungicidal concentration (MBC/MFC) values. The plant pathogenic bacteria Pseudomonas syringae, Xanthomonas hortorum, Erwinia carotovora, and fungi: Fusarium culmorum, Alternaria alternata, Botrytis cinerea, Epicoccum purpurascens, Cladosporium cladosporioides, Phoma strasseri, and Pythium debaryanum were tested. The EOs revealed a stronger inhibitory effect against fungal growth in comparison to bacterial growth (MIC: 0.016-2 µL/mL for fungi and 0.125-4 µL/mL for bacteria). Common thyme and Greek oregano EOs indicated stronger antimicrobial power than common oregano EO. These results were associated with the chemical profile of the analysed EOs. The growth of examined bacteria and fungi strains (in particular, X. hortorum, F. culmorum, and P. debaryanum) were negatively correlated with the content of phenolic monoterpenes and monoterpene hydrocarbons. Among the tested strains, P. strasseri turned out to be the most sensitive (MIC 0.016 µL/mL) and E. carotovora the most resistant (MIC 0.250-4 µL/mL) to all investigated EOs.

با توجه به تاثیرات منفی نگهدارنده های شیمیایی بر سلامت مصرف‌کنندگان، توجه مراجع قانونی و صنایع غذایی بر کاربرد اسانس‌ها و عصاره‌های گیاهی بعنوان نگهدارنده‌های طبیعی در مواد غذایی متمرکز شده است. در این پژوهش تاثیر اسانس‌های ریحان و مریم گلی کبیر بر رشد لیستریا مونوسیتوژنز و آسپرژیلوس فلاووس طی دوره نگهداری پنیر سفید ایرانی مورد مطالعه قرار گرفت. روش‌های بکار رفته در این تحقیق مشتمل بر تعیین حداقل غلظت مهارکنندگی رشد (MIC)، حداقل غلظت باکتری‌کشی (MBC) و حداقل غلظت قارچ‌کشی (MFC) اسانس‌ها، تعیین تاثیر غلظت‌های مختلف اسانس‌ها بر رشد لیستریا و آسپرژیلوس در پنیر طی دوره نگهداری محصول بود. ترکیبات اصلی اسانس مریم گلی کبیر شامل لینالیل استات، لینالول و اسانس ریحان شامل لینالول و آلفا-کادینول بود.MIC و MBC اسانس مریم گلی، به ترتیب، معادل 015/0% و 02/0% و اسانس ریحان برابر با 05/0% و 06/0% برای لیستریا بود. همچنین، MIC و MFC در برابر آسپرژیلوس برای اسانس مریم گلی معادل 5/0% و 65/0% و برای اسانس ریحان برابر با 6/0% و 8/0% بدست آمد. غلظت 35/0% اسانس مریم گلی و 5/0% اسانس ریحان از تولید اسپور توسط قارچ در محیط کشت جلوگیری نمود. اسانس مریم گلی در غلظت 1% طی دوره نگهداری پنیر از رشد آسپرژیلوس بطور کامل بازداری نمود و جمعیت لیستریا را نسبت به شاهد log 6 کاهش داد. اسانس ریحان تاثیر ضدمیکربی ضعیف‌تری نسبت به اسانس مریم گلی کبیر نشان داد.

The isolated essential oils from seven air-dried plant species were analyzed by gas chromatography-mass spectrometry (GC-MS). Thymus vulgaris (thyme), Origanum vulgare (oregano), and Origanumdictamus (dictamus) essential oils were found to be rich in phenolic compounds representing 65.8, 71.1, and 78.0% of the total oil, respectively. Origanum majorana (marjoram) oil was constituted of hydrocarbons (42.1%), alcohols (24.3%), and phenols (14.2%). The essential oil from Lavandula angustifolia Mill. (lavender) was characterized by the presence of alcohols (58.8%) and esters (32.7%). Ethers predominated in Rosmarinus officinalis (rosemary) and Salvia fruticosa (sage) essential oils, constituting 88.9 and 78.0%, respectively. The radial growth, conidial germination, and production of Penicillium digitatum were inhibited completely by oregano, thyme, dictamus, and marjoram essential oils at relatively low concentrations (250-400 microg/mL). Lavender, rosemary, and sage essential oils presented less inhibitory effect on the radial growth and conidial germination of P. digitatum. Conidial production of P. digitatum was not affected by the above oils at concentrations up to 1000 microg/mL. Apart from oregano oil, all essential oils were more effective in the inhibition of conidial germination than of radial growth. The monoterpene components, which participate in essential oils in different compositions, seem to have more than an additive effect in fungal inhibition.

BackgroundStreptococcus mutans (S. mutans) is considered the most relevant bacteria during the transition of the non-pathogenic commensal oral microbial community to plaque biofilms that promote the development of dental caries. Oregano (Origanum vulgare L.), is a universally natural flavoring and its essential oil has been demonstrated to have good antibacterial effects. However, the specific antibacterial mechanism of oregano essential oil (OEO) against S. mutans is still not completely understood.MethodsIn this work, the composition of two different OEOs was determined by GC‒MS. Disk-diffusion method, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined to assess their antimicrobial effect on S. mutans. The inhibition of acid production, hydrophobicity, biofilm formation and real-time PCR for gtfB/C/D, spaP, gbpB, vicR, relA and brpA mRNA expression by S. mutans were assessed to preliminarily investigate the mechanisms of action. Molecular docking was performed to simulate the interactions with the virulence proteins and active constituents. MTT test using immortalized human keratinocytes cells was also performed to investigate cytotoxicity.ResultsCompared with the positive drug Penicillin /streptomycin 100X (DIZ: 34.13 ± 0.85 mm, MIC: 0.78125 μL/mL, MBC: 6.25 μL/mL), the essential oils of Origanum vulgare L. (DIZ: 80 mm, MIC: 0.625μL/mL, MBC:2.5μL/mL) and Origanum heracleoticum L. (DIZ: 39.67 ± 0.81 mm, MIC: 0.625μL/mL, MBC: 1.25μL/mL) could also exhibit similar effects to inhibit the acid production and reduce the hydrophobicity and biofilm formation of S. mutans at 1/2-1MIC concentration. And gene expression of gtfB/C/D, spaP, gbpB, vicR and relA were found to be downregulated. Due to the composition of essential oils from different sources being highly variable, through effective network pharmacology analysis, we found that OEOs contained many effective compounds, like carvacrol and its biosynthetic precursors γ-terpinene and p-cymene, which may directly target several virulence proteins of S. mutans. Besides, no toxic effect was instigated by OEOs at 0.1 μL/mL in the immortalized human keratinocytes cells.ConclusionThe integrated analysis in the present study suggested that OEO might be a potential antibacterial agent for the prevention of dental caries.

This research examined the antimicrobial effect of Lavandula stoechas (lavender) and Origanum majorana (marjoram) essential oil against three mastitis-causing pathogens: Staphylococcus aureus, Streptococcus agalactiae, and Escherichia coli. Gas chromatography-mass spectrometry (GC/MS) analysis revealed that the main components of the lavender and marjoram oils were 17-Pentatriacontene, Linalyl acetate, Eucalyptol, linalool and 3-Cyclohexene-1-ol,4-methyl-1-(1-methylethyl)-,(R)-, α-terpineol, P-cymene, respectively. Broth dilution testing was performed using autoclaved whole milk instead of broth to determine minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of essential oils alone and in combination. In addition, time-kill assay of lavender and marjoram oils were determined in milk up to 24 h. MIC values ranged from 3.12 - 4.37% v/v and MBC between 6.25 - 8.75% v/v for the lavender. The MIC and MBC of the marjoram ranged from 0.62 - 1.87% v/v and 1.25 - 3.75% v/v, respectively. The MIC ranged from 2.5 - 5% v/v and MBC between 5 - 10% v/v for lavender + marjoram combination. In time-kill assays, the presence of lavender and marjoram oils at a sub-MIC concentration significantly reduced the bacterial population in 4, 10 and 24 h. Generally, essential oil of marjoram had greater antibacterial activity than lavender against all mastitis-causing pathogens tested and has the potential to be evaluated as an alternative or adjunct to antibiotics in the treatment of bovine mastitis.

The antibacterial effects of essential oils from Serbian cultivated plants, Thymus vulgaris L. (Lamiace) and Lavandula angustifolia L. (Lamiace) on different bacteria were investigated, with an emphasis on an antibacterial activity-chemical composition relationship. Essential oil was obtained from airdried aerial parts of the plants by hydrodistillation for 3 h using a Clevenger-type apparatus. The essential oil analyses were performed simultaneously by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) systems. The main constituents of thyme oil were thymol (59.95%) and p-cymene (18.34%). Linalyl acetate (38.23%) and linalool (35.01%) were main compounds in lavender oil. The antibacterial activity of the essential oils samples was tested towards 5 different bacteria: laboratory control strain obtained from the American Type Culture Collection and clinical isolates from different pathogenic media. Gram negative bacteria were represented by Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 43895 and Salmonella enteretidis ATCC 9027 while researched Gram positive strains were Bacillus cereus ATCC 8739 and Staphylococcus aureus ATCC 25923. A broth microdilution method was used to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Essential oils from thyme have been found to have antimicrobial activity against all microorganisms tested, with a range of MIC values from 0.025 to 0.10 l/ml and MBC values from 0.05 to 0.78 l/ml. Lavender oils demonstrated MIC values from 0.025 to 0.20 l/ml and MBC values from 0.05 and 0.78 l/ml. Reference antibiotic tetracycline was active in concentrations between 0.025 and 0.05 l/ml. The Gram-positive bacteria were more sensitive to the essential oil of thyme, while Gram-negative bacteria were more sensitive to the essential oil of lavender. Essential oils from thyme and lavender may be used at low concentrations for prevention and treatment of infective diseases in animals and humans caused by pathogenic bacterial species.

Essential oils are concentrated natural extracts derived from plants, which were proved to be good sources of bioactive compounds with antioxidative and antimicrobial properties. This study followed the effect of some commonly used essential oils in micellar and aqueous extract on some of the most common pathogenic bacteria. Frankincense, myrtle, thyme, lemon, oregano and lavender essential oils were tested against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa. Both micellar and aqueous extracts were used for determination of their minimal inhibitory (MIC) and bactericidal concentrations (MBC). The most active oils were oregano, thyme, lemon and lavender, while the least active were frankincense and myrtle. Oregano oil presented up to 64 times lower MICs/MBCs than ethylic alcohol, if considered as standard, on all bacteria. Most susceptible bacteria were the Gram-positive cocci, including methicillin resistant S. aureus, while the most resistant was P. aeruginosa. With some exceptions, the best activity was achieved by micelles suspension of essential oils, with MICs and MBCs ranging from 0.1% to > 50% v/v. Only oregano and lavender aqueous extracts presented bactericidal activity and only on K. pneumoniae (MIC = 6.3%). Thyme, lemon and oregano oils present significantly lower overall average MICs for their micellar form than for their aqueous extracts. The present results may suggest some formulas of colloid or micelle suspensions of whole essential oils such as oregano, thyme or lemon oil, that may help in antimicrobial fight. Aqueous extracts of oregano or thyme oil with good antibacterial activity could also be used in selected cases.