ANTIBACTERIAL POTENTIAL OF ESSENTIAL OILS FROM MELALEUCA ALTERNIFOLIA, MENTHA PIPERITA, AND ROSMARINUS OFFICINALIS AGAINST STAPHYLOCOCCUS PSEUDINTERMEDIUS ISOLATES

Essential oils (EOs) and honeybee products (e.g., honey and propolis) are natural mixtures of different volatile compounds that are frequently used in traditional medicine and for pathogen eradication. The aim of this study was to evaluate the antibacterial properties of tea tree (Melaleuca alternifolia) EO (TTEO), Rosmarinus officinalis EO (ROEO), manuka-based gel, and propolis against 23 strains of Staphylococcus pseudintermedius (SP) isolated from canine pyoderma. Antimicrobial resistance screening was assessed using a panel of nine antimicrobial agents coupled with a PCR approach. An aromatogram was done for both EOs, using the disk diffusion method. The minimum inhibitory concentration (MIC) was determined for all the compounds. Among the 23 SP strains, 14 (60.9%) were multidrug-resistant (MDR), 11 strains (47.8%) were methicillin-resistant (MRSP), and 9 (39.1%) were non-MDR. The mean diameter of the inhibition zone for Melaleuca and Rosmarinus were 24.5 ± 8.8 mm and 15.2 ± 8.9 mm, respectively, resulting as statistically different (p = 0.0006). MIC values of TTEO and ROEO were similar (7.6 ± 3.2% and 8.9 ± 2.1%, respectively) and no statistical significances were found. Honeybee products showed lower MIC compared to those of EOs, 0.22 ± 0.1% for Manuka and 0.8 ± 0.5% for propolis. These findings reveal a significant antibacterial effect for all the tested products.

Antimicrobial capabilities of non-spermicidal concentrations of tea tree (Melaleuca alternifolia) and rosemary (Rosmarinus officinalis) essential oils on the liquid phase of refrigerated swine seminal doses

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.

A multitude of phytopharmacological studies have pointed out the extraordinary biological potential owned by some herbal extracts (Ncube et al.; 2008). To establish the delimitations for their therapeutical use; the cytotoxic effect must be also taken into consideration (Gerald Muller and Axel Kramer; 2008). The aim of present research was to assess both the antimicrobial and cytotoxic properties of essential oils obtained from Thymus vulgaris; Salvia officinalis; Mentha piperita; Rosmarinus officinalis; Lavandula angustifolia and Mellisa officinalis. By determing the antibacterial activity (broth microdilution method) against the reference strain Staphylococcus aureus ATCC 25923 and; in parallel; the cytotoxicity on cultured canine leukocytes (viable cells count using Trypan Blue exclusion test); the biocompatibility index (BI) was established for each tested herbal extract. BI was defined as the ratio of the concentration at which 50% of the canine leucocytes were damaged and the minimum bactericidal concentration (MBC). All herbal extracts displayed antibacterial potential; but also some of them proved to be highly cytotoxic to the canine leukocytes as a significant decrease in the final number of viable cells was observed. Still; in case of Mellisa officinalis and Rosmarinus officinalis essential oils; the cytotoxic effect was absent for all the tested concentrations; indicating that these two essential oils could be used for their antimicrobial activity. However; further tests should be performed on their efficacy and side effects.

Chemical composition of Mentha pulegium and Rosmarinus officinalis essential oils and their antileishmanial, antibacterial and antioxidant activities

Antimicrobial resistance, an ever-growing global crisis, is strongly linked to the swine production industry. In previous studies, Melaleucaalternifolia and Rosmarinusofficinalis essential oils have been evaluated for toxicity on porcine spermatozoa and for antimicrobial capabilities in artificial insemination doses, with the future perspective of their use as antibiotic alternatives. The aim of the present research was to develop and validate in vitro and ex vivo models of porcine uterine mucosa for the evaluation of mucosal toxicity of essential oils. The in vitro model assessed the toxicity of a wider range of concentrations of both essential oils (from 0.2 to 500 mg/mL) on sections of uterine tissue, while the ex vivo model was achieved by filling the uterine horns. The damage induced by the oils was assessed by Evans Blue (EB) permeability assay and histologically. The expression of ZO-1, a protein involved in the composition of tight junctions, was assessed through immunohistochemical and immunofluorescence analysis. The results showed that low concentrations (0.2–0.4 mg/mL) of both essential oils, already identified as non-spermicidal but still antimicrobial, did not alter the structure and permeability of the swine uterine mucosa. Overall, these findings strengthen the hypothesis of a safe use of essential oils in inseminating doses of boar to replace antibiotics.

Thirteen commercial Tasmanian essential oils were evaluated for their antimicrobial activity against 14 human pathogens and cosmetic contaminants including Enterococcus hirae, Kocuria rhizophila, Staphylococcus epidermidis, Propionibacterium acnes, Staphylococcus aureus, Escherichia coli, Klebsiella aerogenes, Klebsiella pneumoniae, Pluralibacter gergoviae, Pseudomonas fluorescens, Burkholderia cepacia, Pseudomonas putida, Aspergillus brasiliensis, and Aspergillus fumigatus. The antimicrobial activities of various essential oils were evaluated using the AlamarBlue Cell Viability Assay, covering a testing concentration range from 3.125 to 800 µg/mL. Essential oils were deemed active if their minimum inhibitory concentration (MIC) value was less than or equal to 800 µg/mL. The essential oils of Rosemary (Rosmarinus officinalis ct. α-pinene), Parsley Herb (Petroselinum crispum), and Bitter Fennels (Foeniculum vulgare) demonstrated significant growth inhibitory effects on one microorganism (P. fluorescens) within an MIC value of ≤ 800 µg/mL. Big Badja Gum (Eucalyptus badjensis), Blue Gum (Eucalyptus globulus), Peppermint (Mentha piperita), and Lavender (Lavandula angustifolia) essential oils inhibited the growth of two different microorganisms. Southern Rosalina (Melaleuca ericifolia), Parsley Seed (Petroselinum crispum), Smoky Tea Tree (Leptospermum glaucescens), and Kunzea (Kunzea ambigua) essential oils exhibited an MIC value of less than or equal to 800 µg/mL against 4, 5, 6, and 8 microorganisms respectively. Notably, Coastal Tea Tree (Leptospermum laevigatum) essential oil displayed the most profound antimicrobial activity, inhibiting 11 out of 15 microbial strains within an MIC range of 50–800 µg/mL. The results of the gas chromatography analysis showed that the coastal tea tree essential oil was composed primarily of monoterpenes, with smaller amounts of sesquiterpenes and their oxygenated derivatives. 35 Compounds were identified, representing 95.50% of the compounds in the coastal tea tree essential oil. The main constituents of this essential oil were α-pinene (34.83%), followed by α- and β-eudesmols (10.21% total), and limonene (9.56%).

Escherichia coli biofilms, a major cause of persistent infections, often exhibit resistance to conventional antibiotics. This study investigates the potential of essential oils derived from Eucalyptus camaldulensis, Mentha piperita L., and Rosmarinus officinalis L. as natural alternatives to combat these infections. A comparative analysis of biofilm quantification was done by using 0.5% crystal violet and safranin. The essential oils, characterized by Fourier Transform Infrared Spectroscopy and Gas Chromatography-Mass Spectrometry, demonstrated significant antibacterial activity against diverse Escherichia coli strains, with Minimum Inhibitory Concentration and Minimum Bactericidal Concentration values ranging from 3.13 to 35µg/mL. Gas Chromatography-Mass Spectrometry revealed the presence of 1,8 cineol (90%) in the essential oils from Eucalyptus camaldulensis, mono terpenoids (64%) in the essential oils from Mentha piperita L and D1-2- ethylhexyl chloroformate (94%) in the essential oils from Rosmarinus officinalis L as major components. The essential oils effectively inhibited biofilm formation by 55-96% and eradicated existing biofilms by 57.5-95%. Mechanistic studies revealed that the essential oils induced the release of cellular components, suggesting a novel mode of action. These findings highlight the potential of these oils as promising agents for combating Escherichia coli infections, particularly those caused by biofilm-forming strains. Further research is warranted to optimize this approach for clinical applications and to fully elucidate their mechanisms of action.

Background: Oral candidiasis is caused by the mycotic activity of Candida albicans present in the oral cavity, and it is one of the most common opportunistic infections found in patients with Human Immunodeficiency Virus (HIV)/acquired immune deficiency syndrome (AIDS). The growing resistance and side effects to common antifungal drugs have promoted herbal essential oils as antifungal agents in recent years. In this study, essential oils (EO) of Rosmarinus officinalis (Lamiaceae) were examined for in vitro antifungal activ­ity against Candida species. Purpose: To evaluate the antifungal activity of essential oils of Rosmarinus officinalis (Lamiaceae) and nystatin using the microdilution technique by determining the minimum inhibitory concentration (MIC) and the minimum fungicidal concentration (MFC) of Candida spesies. Methods: This was an experimental laboratory study with a post-test-only design conducted in Dr. Soetomo General Academic Teaching Hospital, Surabaya. Forty isolates consisted of twenty isolates of Candida albicans and twenty isolates of Candida non-albicans were collected. The isolates were tested for antifungal activity using the microdilution on 96-well plates. Result: There was a significant difference from the results of the MIC concentration of rosemary essential 100% to 6.25% microdilution method between nystatin and rosemary essential oil (p < 0.05). Conclusion: The antifungal activity of rosemary essential oil was better than nystatin that the lowest MIC value, which was 6.25%, has been obtained the microdilution method. The minimum fungicidal concentration of rosemary essential oil was 25%, while the minimum fungicidal concentration nystatin was higher than 100%.

Simple SummaryPyoderma is one of the most common diseases in dogs, and Staphylococcus pseudintermedius, a Gram-positive coagulase-positive bacterium, represents the most common infectious agent causing canine pyoderma. Since multidrug-resistant S. pseudintermedius strains have become a relevant threat in veterinary medicine, this study aimed to test the antimicrobial properties of some essential oils (EOs) against S. pseudintermedius strains isolated from dogs suffering from pyoderma. The obtained findings demonstrated a clear in vitro efficacy of some tested EOs against clinical methicillin-resistant and methicillin-sensible S. pseudintermedius strains. The applicability and efficacy of EOs in cases of canine pyoderma supported by S. pseudintermedius could be beneficial for both dogs and pet owners, who are inevitably exposed to this zoonotic bacterium.This study aimed to test in vitro the antimicrobial activity of 11 essential oils (EOs) against four methicillin-resistant Staphylococcus pseudintermedius (MRSP) and four methicillin-susceptible S. pseudintermedius (MSSP) clinical isolates. The obtained findings demonstrated a clear in vitro efficacy of some tested EOs against both MRSP and MSSP strains. Particularly, modal minimum inhibitory concentration (MIC) values ranging from 1:2048 v/v for Melissa officinalis against an MSSP strain to 1:256 v/v for Cymbopogoncitratus against all MRSP strains were observed. The best results, highlighting a modal MIC value of 1:1024 v/v for all tested isolates, was provided by Cinnamomum zeylanicum. Intriguingly, Cinnamomum zeylanicum showed, in many cases, a correspondence between minimum bactericidal concentration (MBC) and MIC values, indicating that the inhibiting dose is also often bactericidal. Moreover, a mild antibacterial and bactericidal activity against both MRSP and MSSP isolates was detected for the other tested EOs. Considering the zoonotic potential of S. pseudintermedius and the increased dissemination of multidrug-resistant strains, the employment of EOs could be useful for the treatment of canine pyoderma. Since antibiotic resistance has become the most urgent issue, from the perspective of the One Health initiative, alternative therapeutic approaches are desirable to limit the use of antibiotics or to improve the efficacy of conventional therapies.

Durability of rubberwood ( Hevea brasiliensis) treated with peppermint oil, eucalyptus oil, and their main components

1281. An Evaluation of Tebipenem In Vitro Activity Against a Panel of Pseudomonas aeruginosa Isolates with Efflux, AmpC, and OprD Mutations

In this study, chemical composition, physicochemical properties and bioactivity of two essential oils of Rosmarinus officinalis extracted from plant material with different drying treatments against Apis mellifera, Varroa destructor and Paenibacillus larvae were assessed. The lethal concentration 50 (LC50) for mites and bees was estimated using a complete exposure method test. The broth microdilution method was followed in order to determine the minimum inhibitory concentrations (MICs) of the essential oils against P. larvae. Physicochemical properties were similar in both the essential oils, but the percentage of components showed certain differences according to their drying treatment. β-Myrcene and 1,8-cineole were the main constituents in the oils. The LC50 for complete exposure method at 24, 48 and 72 h was minor for mites exposed to R. officinalis essential oil dried in oven conditions. MIC values were 700–800 µg mL−1 and 1200 µg mL−1 for R. officinalis dried in air and oven conditions, respectively. The results reported in this research show that oil toxicity against V. destructor and P. larvae differed depending on the drying treatment of the plant material before the distillation of essential oil.

Essential oils (EOs) from Citrus are not only economic, eco-friendly and natural alternatives to chemical preservatives but also have other biological applications. This study aimed to investigate the chemical composition of Citrus species (EOs from C. limonia, C. latifolia, C. sinensis and C. deliciosa fruit peel) to evaluate their in vitro antibacterial activity against Listeria monocytogenes, Yersinia enterocolitica, Staphylococcus aureus, Clostridium botulinum and Bacillus cereus. The chemotaxis model, which was used for evaluating their anti-inflammatory activity, showed that EOs exhibited effective results when the dose was 100 µg/mL. Regarding all antimicrobial activities, minimum inhibitory concentration (MIC) values of EOs were calculated by the broth microdilution method on 96-well microplates. EOs showed satisfactory antifungal activity against Malassezia furfur (MIC values between 32.5 and 62.5 µg/mL). Citrus deliciosa, whose MIC = 95.8 µg/mL, inhibited acetylcholinesterase (AChE) more selectively. All EOs from Citrus spp. fruit peel showed good antibacterial activity against Yersinia enterocolitica (MIC = 62.5 µg/mL) and Staphylococcus aureus (MIC = 62.5 µg/mL), mainly the EO from C. deliciosa whose MIC values were 50 µg/mL for both. EOs were moderately active against Clostridium botulinum, Bacillus cereus and Listeria monocytogenes since MIC values ranged from 100 μg/mL to 400 μg/mL. Both GC-FID and GC-MS analyses revealed that the single major constituent determined in EOs is the terpene limonene. EOs from Citrus may be important active ingredients of several products to prevent bacterial growth in food, to attack the fungus that causes seborrheic dermatitis and to treat inflammatory processes. In short, the promising antiacetylcholinesterase activity of EOs under evaluation was attributed to the high concentration of the monoterpene limonene

Mastitis is one of the most common and costly diseases affecting dairy cows worldwide. Since antibiotic resistance has become a global threat to both animal and human health, it is becoming more urgent to continuously search for new therapeutical alternatives for the control and treatment of bovine mastitis. Hence, our research aimed to test the therapeutic use of two essential oils (EOs) based on their chemical composition, antibacterial and antioxidant potential. The present study was conducted by collecting milk samples from the cows diagnosed with clinical or subclinical mastitis with the aim of isolating and identifying bacterial strains. The antioxidant potential of essential oils of Menthae piperitae (MP) and Melissa officinalis (MO) was evaluated in several in vitro assays. In the MP EO, a total of 38 compounds were identified, with menthol as the dominant compound, whereas in MO EO 51 compounds were identified. Furthermore, the values of minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) have been used to quantitatively measure the antibacterial activity of each essential oil. In accordance with which, MP EO samples exhibited a higher degree of antibacterial activity than MO EO. Thus, EOs have been shown to be promising alternatives to antibiotics because of their availability, biodegradability, and lower risk of side effects as compared with conventional, antimicrobial treatment. Nevertheless, further clinical studies are needed to test the potential role of EOs in treating mastitis in dairy cows.