Antibacterial Effects Of Essential Oils Research Articles

Synergistic effects of essential oils and phenolic extracts on antimicrobial activities using blends of Artemisia campestris, Artemisia herba alba, and Citrus aurantium.

This study explores the synergistic antibacterial effects of essential oils (EOs) and phenolic extracts from three plants against foodborne pathogenic bacteria. The present work aimed to investigate the synergistic effects of the binary and the ternary combinations of extracts using different blend proportions of the following plant extracts: Artemisia campestris (AC), Artemisia herba alba (AHA), and Citrus aurantium (CA). The antimicrobial activities of EOs and phenolic extracts were determined and evaluated against five strains. For the EOs, the results of the DIZ showed the existence of synergism for different combinations of binary blends, such as AC/AHA or AHA/CA against Escherichia coli, and AC/CA against Enterobacter faecalis. In addition, ternary blends of AC:AHA:CA at a ratio of 1/6:2/3:1/6 exhibited a synergy effect, as measured by the CI, against E. coli. On the other hand, for the phenolic extracts, synergistic effects were noticed for binary blends of AC/CA at different ratios against E. coli, E. faecalis, and Pseudomonas aeruginosa strains. Similarly, ternary blends of phenolic extracts presented synergy against E. coli, E. faecalis, P. aeruginosa strains, and even C. albicans. In this case, the blending ratios were crucial determining factors for maximizing the synergy effect. The study established that the proportion of a single drug could play an essential role in determining the bioefficacy of a drug combination treatment. Therefore, the results showed the importance of studying the modulation of antibacterial activities based on the proportions of extracts in the mixture and finding the range of proportions (as determined by SLMD) that have a synergistic/additive/antagonistic effect with no or low side effects, which can be used in a food preservation system.

Chemical Composition, Anti-bacterial Activity and Molecular Docking Studies of Essential Oil Isolated from Sa Sam Nam (Launaea sarmentosa).

Launaea sarmentosa, also known as Sa Sam Nam, is a widely used remedy in Vietnamese traditional medicine and cuisine. However, the chemical composition and bioactivity of its essential oil have not been elucidated yet. In this study, we identified 40 compounds (98.6% of total peak area) in the essential oil via GC-MS analysis at the first time. Among them, five main compounds including Thymohydroquinone dimethyl ether (52.4%), (E)-α-Atlantone (9.0%), Neryl isovalerate (6.6%), Davanol D2 (isomer 2) (3.9%), and trans-Sesquisabinene hydrate (3.9%) have accounted for 75.8% of total peak area. The anti-bacterial activity of the essential oil against 4 microorganisms including Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa has also investigated via agar well diffusion assay. The results showed that the essential oil exhibited a strong antibacterial activity against Bacillus subtilis with the inhibition zones ranging from 8.2 to 18.7 mm. To elucidate the anti-bacterial effect mechanism of the essential oil, docking study of five main compounds of the essential oil (Thymohydroquinone dimethyl ether, (E)-α-Atlantone, Neryl isovalerate, Davanol D2 (isomer 2), and trans-Sesquisabinene hydrate) against some key proteins for bacterial growth such as DNA gyrase B, penicillin binding protein 2A, tyrosyl-tRNA synthetase, and dihydrofolate reductase were performed. The results showed that the main constituents of essential oil were highly bound with penicillin binding protein 2A with the free energies ranging -27.7 to -44.8 kcal/mol, which suggests the relationship between the antibacterial effect of essential oil and the affinity of main compounds with penicillin binding protein. In addition, the free energies of main compounds of the essential oil with human cyclooxygenase 1, cyclooxygenase 2, and phospholipase A2, the crucial proteins related with inflammatory response were less than diclofenac, a non-steroidal antiinflammatory drug. These findings propose the essential oil as a novel and promising anti-bacterial and anti-inflammatory medicine or cosmetic products.

Evaluation of the Antibacterial Activity of Gentamicin in Combination with Essential Oils Isolated from Different Cultivars and Morphological Parts of Lavender (Lavandula angustifolia Mill.) against Selected Bacterial Strains.

The aim of the study was to investigate the antibacterial effects of essential oils isolated from different cultivars and morphological parts of lavender (Lavandula angustifolia Mill.) in combination with the aminoglycoside antibiotic gentamicin. This in vitro study analyzed the effectiveness of the combinations of gentamicin and lavender essential oils against the following strains: Staphylococcus aureus ATCC 25923, Staphylococcus aureus MRSA and Pseudomonas aeruginosa ATCC 9027. The effect of the combination of lavender oils with gentamicin was tested using the checkerboard method. A synergistic effect against S. aureus strain ATCC 25923 was found when gentamicin was combined with lavender essential oils isolated from flowers and leafy stalks (flowers: 'Blue River' FICI-0.192; 'Ellagance Purple' FICI-0.288; leafy stalks: 'Blue River' FICI-0.192; 'Ellagance Purple' FICI-0.320). A synergistic effect was also observed for the combination of gentamicin with lavender essential oils from flowers against the resistant strain of S. aureus (MRSA) ('Blue River' FICI-0,191; 'Ellagance Purple' FICI-0.263), as well as for the essential oils from leafy stalks ('Blue River' FICI-0.076; 'Ellagance Purple' FICI-0.089). No interaction was observed for the combination of studied essential oils with gentamicin against P. aeruginosa strain ATCC 9027 (FICI = 1.083-1.300).

Application of mixture design for the optimum antibacterial action of chemically-analyzed essential oils and investigation of the antiadhesion ability of their optimal mixtures on 3D printing material

Contamination of food and medical devices has become a serious public health concern. Therefore, this work intended to assess the single and combined antibacterial effect of essential oils (EOs) obtained from Clinopodium nepeta, Ruta montana, and Dittrichia viscosa, through mixture design approach. In addition, the anti-adhesive action of the obtained optimal mixtures of EOs was investigated against bacterial adhesion on 3D printed surface, widely used in food and medical industries. Indeed, Chromatography Gas/Mass spectrometry (CG/MS) analysis showed that pulegone (30.2%), piperitenone oxide (15.71%), and limonene (10.32%), mainly characterized the Clinopodium nepeta essential oil (CNEO), whereas Ruta montana essential oil (RMEO) was dominated by 2-undecanone (46.13%), and 2-nonanone (20.53%). By contrast, the Dittrichia viscosa essential oil (DVEO) principally contained (E)-nerolidol (32.21%), τ-muurolol (18.17%), and α-eudesmol (10.36%). The obtained optimum mixtures revealed that the binary combination consisting of 36% of RMEO, 64% of CNEO certified the maximal inhibition against Staphylococcus aureus (S. aureus), while a formulation of 25%, 50%, and 25% of RMEO, CNEO, and DVEO respectively, was associated to the ideal restriction of Pseudomonas aeruginosa (P. aeruginosa). The time-kill analysis showed that all studied EOs are able to eradicate the total growth (bactericidal action) of S. aureus and P. aeruginosa at twice-minimal inhibitory concentration (2xMIC) after 12 h. Interestingly, the contact angle method and environmental scanning electron microscopy (ESEM) analysis reported that the optimal EOs mixtures are effective in preventing biofilm formation by modification of physico-chemical parameters of the 3D printing resin surface and complete inhibition of bacterial adhesion on the material surface. Thereby, the interaction between EOs might be applied as natural preservatives in the food and medical industries.

Short communication: Antibacterial effects of essential oils from Cinnamomum cassia bark and Eucalyptus globulus leaves-The involvements of major constituents.

Essential oils from Cinnamomum cassia bark and Eucalyptus globulus leaves have been traditionally applied for bacterial infections, through both of aromatherapy and oral application. (E)-cinnamaldehyde and 1,8 cineole have been identified as their major secondary metabolites, and are also generally considered as the main active ingredients responsible for their medicinal applications. However, ethnobotanical doctors still prefer to use whole essentials oils over purified compounds in bacterial infections. We therefore hypothesized that multi-compound extracts might exert better effects than isolated ingredients. In order to verify the hypothesis about advantages of whole materials, we examined antibacterial properties of the 2 plant essential oils in the comparison with their isolated major compounds, such as (E)-cinnamaldehyde and 1,8 cineole. Effects of liquid- and vapor-phase were examined on a set of 6 gram-positive and -negative bacteria, applying broth dilution, agar well diffusion and disc volatilization methods. In all 3 investigations, we observed that whole cinnamon and eucalyptus oils, with the lower concentrations of (E)-cinnamaldehyde (89.1%) and 1,8 cineole (61.2%), were able to induce better effects than the purified active compounds (≥ 99%). These results partly explain the advantages of using whole essential oils over isolated ingredients, and therefore support the application of traditional dosage forms for bacterial infections in ethnomedicine.

THE EFFECT OF ESSENTIAL OILS ON PATHOGENIC BACTERIA IN MEAT

Meat is a nutritionally valuable food which is susceptible to microbiological contamination and spoilage. Major foodborne pathogenic bacteria, such as Salmonella spp., Listeria monocytogenes and Yersinia enterocolitica, are often associated with meat. These causative factors are at the top of the list of reported zoonoses in humans. In order to increase the microbiological quality of meat, alternative substances have been used in recent decades, including essential oils, compounds obtained by extraction from plants, which are a “safe” alternative to chemical and synthetic additives, in order to achieve antimicrobial and antioxidant effects. Many studies show the antibacterial effect of essential oils. The effect of essential oils on bacteria includes the inhibition of growth (bacteriostatic effect) or destruction of bacteria (bactericidal effect). This paper presents commercially available essential oils recognized as safe for use in food industry, their antibacterial effects against food-borne bacteria in vitro, the mechanisms of action of these essential oils on Gram-positive and Gram-negative bacteria, as well as their application on a meat model.

Antibacterial effect of essential oils and their components against Xanthomonas arboricola pv. pruni revealed by microdilution and direct bioautographic assays.

Bacterial spot of stone fruits caused by Xanthomonas arboricola pv. pruni (Xap) is one of the most significant diseases of several Prunus species. Disease outbreaks can result in severe economic losses while the control options are limited. Antibacterial efficacy of essential oils (EOs) of thyme, cinnamon, clove, rosemary, tea tree, eucalyptus, lemon grass, citronella grass, and lemon balm was assessed against two Hungarian Xap isolates. The minimal inhibitory concentration (MIC) was determined by broth microdilution assay and for the identification of active EOs' components a newly introduced high-performance thin-layer chromatography (HPTLC)-Xap (direct bioautography) method combined with solid-phase microextraction-gas chromatography/mass spectrometry (SPME-GC/MS) was applied. All EOs inhibited both bacterium isolates, but cinnamon proved to be the most effective EO with MIC values of 31.25 µg/mL and 62.5 µg/mL, respectively. Compounds in the antibacterial HPTLC zones were identified as thymol in thyme, trans-cinnamaldehyde in cinnamon, eugenol in clove, borneol in rosemary, terpinen-4-ol in tea tree, citral (neral and geranial) in lemon grass and lemon balm, and citronellal and nerol in citronella grass. Regarding active compounds, thymol had the highest efficiency with a MIC value of 50 µg/mL. Antibacterial effects of EOs have already been proven for several Xanthomonas species, but to our knowledge, the studied EOs, except for lemon grass and eucalyptus, were tested for the first time against Xap. Furthermore, in case of Xap, this is the first report demonstrating that direct bioautography is a fast and suitable method for screening anti-Xap components of complex matrices, like EOs.

Chemical Composition and Biological Properties of Essential Oils of Zingiber officinale, Citrus sinensis, Cinnamomum camphora, and Cinnamomum cassia

Essential oils have recently received a lot of attention due to their numerous uses in natural functional ingredients, Cosmetics, pharmaceutical formulations, and biomedical products. In our research,, the chemical composition and biological effects of four commercial essential oils obtained extracted from four different plants, Zingiber officinale (Ginger), Citrus sinensis (Orange), Cinnamomum camphora (Camphor), and Cinnamomum cassia (Cinnamon cassia) were analyzed and determined. GC-MS was used to analyze the chemical composition of four essential oils. The disc diffusion technique, minimal inhibition concentration (MIC) and minimum bactericidal concentration (MBC) analysis were used to determine the antibacterial effect of essential oils against Gram positive (Bacillus cereus and Staphylococcus aureus) and Gram negative (Klebsiella pneumonia and Escherichia coli) bacteria. The cytotoxic activity was also evident against cervical carcinoma cells and prostate Carcinoma cells. By GC-MS analysis, the four essential oils, Z. officinale, C. inensis, C. camphor, and C.cassia contained 32, 8, 16, and 9 components in total, respectively. Results, Most of studied essential oils showed antibacterial activities; C. cassia recorded the highest effect against tested strains, followed by C. inensis and C. camphor. C. cassia EO showed a strong inhibitory action against B. cereus and E. coli by inhibiting the region 45.7±0.55, and 40.5±0.53 respectively, while Z. officinale showed no effect against B. cereus, and S. aureus Gve+. The lowest value of MIC and MBC for C. cassia EO is ∼25 μL/mL against B.cereus. C. cassia was the most effective against used mammalian Cell Lines (IC50 values of 52.5±1.59 and 47.46±1.28 μg/mL) followed by C. camphora (IC50 values of 53.23±1.68 and 60.64±1.76 μg/mL). Finally, essential oils have shown a good alternative to replace antibiotics and anti cancer drugs.

Essential oil composition and antimicrobial activity of Glaucosciadium cordifolium (Boiss.) Burtt. & Davis

Glaucosciadium cordifolium (Boiss.) Burtt. & Davis, which is a monotypic species naturally grown in Turkey belonging to the Apiaceae (Umbelliferae) family. In this study, the essential oil obtained from G. cordifolium was analyzed and evaluated for its antimicrobial effects. In chemical studies, the analyzes of essential oil compounds obtained from the aerial parts of plants by hydrodistillation were carried out with GC-FID and GC-MS. In total, 23 compounds were identified making up 98.7% of the total volatile constituents. Sabinene (42.1%), α-pinene (17.1%), and α-phellandrene (10.1%) were found as the main constituents in the oil. In antimicrobial studies, the anticandidal and antibacterial effects of essential oils were tested against 14 pathogenic microorganisms according to the standard protocols of the Clinical Laboratory Standards Institute (CLSI). It has been determined that essential oils have a very weak inhibitory effect when compared with standard antibacterial agents. MIC values of 1800, 3600 µg/Ml, and higher were determined. In addition, it was determined that it showed inhibitory effects, especially against C. krusei at a concentration of 250 µg/mL, with MIC values ranging from 250 to 2000 µg/mL.

Antibiofilm and antibacterial effects of essential oils extracted from plants on Staphylococcus aureus

Staphylococcus aureus is a major pathogen among bacterial infections, also having the ability to produce biofilm, thus becoming tolerant and resistant to antibiotics and immune responses. Essential oil extracted from plants has shown broad-spectrum antibacterial and antibiofilm activities against bacteria. In this study it was evaluated whether rosemary, clove and cinnamon essential oil exert antibacterial and antibiofilm activities against S. aureus in vitro. The essential oils were purchased and their chemical composition was identified by gas chromatography and mass spectrometry (GC-MS). Antibiofilm and antibacterial effects were assessed by the 96-well microtiter plate adhesion assay. The highest antimicrobial and antibiofilm activity were observed with 3% and 6% cinnamon essential oil while the essential oil of clove and rosemary did not show satisfactory results. These results support new antimicrobial therapies against S. aureus infections and biofilm formation, using cinnamon essential oil, thus contributing to both human and veterinary medicines.

Antibacterial Effect of Essential Oil Extracted from Cupressus macrocarpa Leaves Against Several Bacterial Strains

Cupressus macrocarpa (C.macrocarpa) is an evergreen tree with medicinal uses. The essential oil of C. macrocarpa possess a powerful antimicrobial effect and antifungal effect against several bacteria and fungi. We aimed of this study to evaluate the antibacterial activity of C.macrocarpa. Fresh leaves of C.macrocarpa were collected and dried in the shade at room temperature. Essential oil was obtained using hydro distillation and yield was recorded. The antibacterial activity of the essential oil against Staphylococcus aureus, Pseudomonas aeruginosa and Proteus vulgaris was examined and minimal inhibitory concentration (MIC) was determined using microdilution assay. As a result, the yield of essential oil from dried and fresh leaves was 0.39% and 0.4% respectively. The MIC was 0.01 (v/v) for both Staphylococcus aureus and Proteus vulgaris, where the essential oil exhibited lower activity against Pseudomonas aeruginosa with MIC of 0.04 (v/v). These results show the importance of using Cupressus macrocarpa essential oil to treat infection of several known resistant bacteria.

CHEMICAL CONSTITUENTS AND ANTIBACTERIAL PROPERTIES OF KITAGAWIA BAICALENSIS (REDOW. EX WILLD.) PIMENOV ESSENTIAL OILS

Kitagawia baicalensis (Redow. ex Willd.) Pimenov (Umbelliferae) is a perennial monocarpic plant with Siberian-Mongolian type of habitats. Decoction of flowers and roots has been used in Tibetan medicine for intoxication and as diuretic agent to treat edema. The essential oils of the aerial part of K. baicalensis growing within the territory of the Republic of Buryatia were obtained by steam distillation method. The isolated essential oils were yellow oily liquids, lighter than water, with characteristic pleasant odour. The qualitative composition and quantitative content of the components of essential oils were determined by GC/MS. 26 compounds with aromatic, mono- and sesquiterpenoid structures were identified in the composition of essential oils. The main components of the essential oils of the aerial part of the Kitagawia baicalensis from Buryatia were limonene (34.40%), β-myrcene (21.10%), γ-terpinene (12.60%), β-elemen (5.70%), sabinene (5.30%), germacren B (3.20%) and germacrene D (3.10%). Monoterpenoids (83.00%) predominated in general composition of essential oils. The content of compounds with sesquiterpenoid structure was 14.70%. The group of aromatic compounds was represented only by p-cymene (2.30%). Bactericidal and bacteriostatic activities of essential oils against Bacillus cereus, Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica, Aspergillus niger, Candida albicans were determined in this paper. The most pronounced antibacterial effect of essential oils was found against Streptococcus pyogenes (1 : 64 dilution).

Antibacterial Effect of Essential Oil on Staphylococcus Aureus-resistant Strain (MRSA), the Causative Agent of Dermatitis

The emergence of multidrug-resistant microorganisms represents a global challenge owing to the lack of new effective antimicrobial agents. Essential oils could be an alternative to antibiotics because of their anti-inflammatory, antiviral, antibacterial, and antibiofilm activities. Therefore, this study aimed to investigate the antibacterial activity of essential oils as an alternative to antibiotics. In the present study, we cultured methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) with two concentrations (0.5% and 1.0%) of 17 types of essential oils and the antibiotic oxacillin as the control. The optical density of the culture suspensions at 600 nm was determined to assess the effect of the essential oils on MRSA. At 0.5% concentration, 8 essential oils demonstrated higher antibacterial activity than oxacillin, with palmarosa, melissa true, and rose geranium showing the highest antibacterial activity. At 1% concentration, 13 essential oils showed higher antibacterial activity than oxacillin, with melissa true, palmarosa, lemongrass, and rosemary verbenone showing the highest antibacterial activity. Furthermore, essential oils isolated from leaves showed higher antibacterial ability. Overall, the antibacterial activity of essential oils against MRSA varied with the concentration, type, and extraction site. Therefore, our study provides a basis for the selection and use of essential oils for antibacterial activity against MRSA.

Evaluation of in vitro antibacterial effect of essential oil and some herbal plant extract used against mastitis pathogens.

Mastitis in dairy cattle is a highly prevalent infectious disease, caused by various pathogens, mainly Staphylococcu aureus and Escherichia Coli, considerable economic loss worldwide. The aim of this study was to evaluate the in vitro activity of Herbal plants used against S. aureus and E. coli bacteria which are the causative agents of mastitis. Therefore, in this study we investigate the antimicrobial effect of plant to evaluate the in vitro antibacterial activity of squaw mint (Mentha pulegium L., Lamiaceae family), catnip (Nepeta cataria L., Lamiaceae), lemon balm (Melissa officinalis L., Lamiaceae), for mastitis treatment. Solutions prepared in fixed oils, against S. aureus and E. coli bacteria which are the main agents of mastitis. Isolation and antibiotic susceptibility analyses of milk samples taken from 100 subclinical mastitis dairy cows were performed. The antibacterial properties of the solutions were analysed by a disk diffusion method. In the bacterial isolation, S. aureus was determined 97.7% and E. coli 53.5% positive of cows with mastitis. Antibacterial susceptibility test of the Lemon balm extract and essential oil showed maximum zone of inhibition against S. aureus 30µl (23mm), followed by 20µl (19mm), E. coli (19mm) and 10µl (5-7mm), of the same extract against the Gram-positive bacteria. The ethanol extracts show the similar activity against the Gram-negative bacteria at 30, 20, and 10µl (18-20mm). Followed by S. aureus, when the zone areas for the susceptible solutions (Lemon balm, and essential oil) and the control group were compared, determined that there was little difference between for S. aureus and E. coli. This study hence indicated that in vitro cultured plantlets of lemon balm and peppermint oil can be used as the alternative method for production of mastitis and cheap source its precursor with antimicrobial activities.

GC-MS Characterization, In Vitro Antioxidant, Antimicrobial, and In Silico NADPH Oxidase Inhibition Studies of Anvillea radiata Essential Oils

Anvillea radiata is a medicinal plant that has been used in traditional phytotherapy in North Africa as a treatment for various illnesses. In this study, we aim to explore the antioxidant, antifungal, and antibacterial effects of essential oils of Anvillea radiata (EOAR) collected in Morocco. EOAR was extracted by the hydrodistillation method, and the phytochemical identification was carried out by gas chromatography-Mass Spectrometry (GC/MS). The antioxidant capacity was evaluated by the 2.2-diphenyl-1-picrylhydrazyl (DPPH) method, ferricyanide method (FRAP) as well as total antioxidant capacity (TAC). Antifungal and antibacterial properties were determined by use of the disc diffusion and minimum inhibitory concentration assays. The microbial strains used in the antimicrobial evaluation were: Aspergillus niger (MTCC 282), Aspergillus flavus (MTCC 9606), Fusarium oxysporum (MTCC 9913), Candida albicans (ATCC 10231), Escherichia coli (ATB 97/BGM), Staphylococcus aureus (ATCC 6633), Bacillus subtills (DSM 6333), and Escherichia coli (ATB 57/B6N). Based on in silico simulations, the inhibitory power of EOAR against nicotinamide adenine dinucleotide phosphate oxidase (NADPH) was evaluated. The yield of the oil was 0.96% wherein 12 compounds were identified including α-cuprenene (33.48%) camphor (21.41%) and α-himachalene (15.88%) as major compounds. The antioxidant capacity showed an IC50 of 32.36 µg/mL (DPPH) and an EC-50 value of 64.60 ± 3.71 µg/mL in the FRAP assay. The total antioxidant capacity showed a concentration of 977.51 ± 22.38 µg AAE/mg (TAC). As for the antimicrobial effects, the inhibition diameter of the studied bacteria ranged from 23.50 ± 2.31 to mm 29.50 ± 2.21 mm, while for fungi, ranged from 25.12 ± 2.82 mm to 11.42 ± 1.90 mm. Minimum Inhibitory Concentration (MIC) ranged from 12.71 ± 1.59 µg/mL to 23.53 ± 0.78 µg/mL for bacterial strains and 10.31 ± 1.34 µg/mL to 22.75 ± 1.06 µg/mL for fungal strains. In silico, among all Anvillea radiata essential oils analyzed, the sesquiterpene γ-dehydro-ar-himachalene, monoterpenoid phenol carvacrol, as well as sesquiterpene α-cadinene were the most active compounds against NADPH oxidase with a glide score of −6.233, −6.082, and −5.057 Kcal/mol, respectively. Taken together, these data showed that EOAR exhibited enormous significance as an antioxidant, antifungal, and antibacterial agent.

Dietary essential oils improves the growth performance, antioxidant properties and intestinal permeability by inhibiting bacterial proliferation, and altering the gut microbiota of yellow-feather broilers

This experiment was conducted to investigate the antibacterial effects of essential oils (EO) in vitro and the influence of EO on growth performance, intestinal morphology and oxidation resistance and cecal microflora of yellow-feathered broilers. A total of 720 one-day-old male yellow feather broilers were randomly assigned into 4 treatments with 6 replicate cages of 30 broilers each. The groups were as follows: CON group (basal diet), EO200 group (basal diet + 200 mg/kg EO), EO400 group (basal diet + 400 mg/kg EO), and EO600 group (basal diet + 600 mg/kg EO). The experiment lasted for 48 d. Results showed that the growth and biofilm formation of avian pathogenic E. coli O78 and Salmonella pullorum were limited by adding EO to the diet (P < 0.05). Besides, birds fed with EO had greater (P < 0.05) average daily feed intake (ADFI), average daily gain (ADG), and body weight (BW) during d 1 to 21, 22 to 42, and 1 to 48 and lower (P < 0.05) feed: gain (F:G) than those fed with basal diet during d 22 to 42 and 1 to 48. Moreover, the activity of antioxidant enzyme and the intestinal permeability were improved in the EO400 and EO600 groups rather than the CON group on d 21 (P < 0.05). There were significant differences in cecal microbial composition and enrichment of metabolic pathways of birds among all groups by 16S-based sequencing. In summary, some dose of EO improved bacteriostatic ability, antioxidant ability, and intestinal health of broilers which contributed to the growth performance improvement of yellow-feathered broilers, which can be a promising antibiotic alternative for improving poultry production.

Antibacterial activity of plant essential oils obtained from Satureja species against Xanthomonas phaseoli pv. phaseoli and Xanthomonas citri subsp. fuscans

In this study, the antibacterial effects of essential oils obtained from different Satureja species (Satureja cuneifolia Ten., Satureja spicigera (C. Koch) Boiss., Satureja thymbra L., Satureja hortensis L. and Satureja cilicica P.H. Davis) against Xanthomonas phaseoli pv. phaseoli (Smith) Vauterin and Xanthomonas citri subsp. fuscans (Burkholder) Starr &amp;amp; Burkholder, which cause common leaf blight in bean plant, were tested. Essential oils were found to significantly inhibit the growth of bacterial strains of both disease agents in vitro, and the lowest concentrations that prevent bacterial growth were determined for both pathogens. The effects of essential oil applications on seed germination, number of infected cotyledons and disease severity were also evaluated. It was determined that essential oils of S. cuneifolia and S. spicigera has no negative effects on seed germination while essential oils of S. hortensis, S. thymbra and S. cilicica caused a little decrease in seed germination compared to the control. As a result of S. cuneifolia + pathogen and S. spicigera + pathogen applications, no infected cotyledons were detected, and it was determined that the disease development caused by two pathogens was prevented by 100%.

Analysis of cell death in &lt;i&gt;Bacillus subtilis&lt;/i&gt; caused by sesquiterpenes from &lt;i&gt;Chrysopogon&lt;/i&gt; &lt;i&gt;zizanioides&lt;/i&gt; (L.) Roberty&lt;i&gt; &lt;/i&gt;

Recently, the antibacterial effects of essential oils have been investigated in addition to their therapeutic purposes. Owing to their hydrophobic nature, they are thought to perturb the integrity of the bacterial cell membrane, leading to cell death. Against such antibiotic challenges, bacteria develop mechanisms for cell envelope stress responses (CESR). In Bacillus subtilis, a gram-positive sporulating soil bacterium, the extracytoplasmic function (ECF) sigma factor-mediated response system plays a pivotal role in CESR. Among them, σM is strongly involved in response to cell envelope stress, including a shortage of available bactoprenol. Vetiver essential oil, a product of Chrysopogon zizanioides (L.) Roberty root, is also known to possess bactericidal activity. σM was exclusively and strongly induced when the cells were exposed to Vetiver extract, and depletion of multi-ECF sigma factors (ΔsigM, ΔsigW, ΔsigX, and ΔsigV) enhanced sensitivity to it. From this quadruple mutant strain, the suppressor strains, which restored resistance to the bactericidal activity of Vetiver extract, emerged, although attempts to obtain resistant strains from the wild type did not succeed. Whole-genome resequencing of the suppressor strains and genetic analysis revealed inactivation of xseB or pnpA, which code for exodeoxyribonuclease or polynucleotide phosphorylase, respectively. This allowed the quadruple mutant strain to escape from cell death caused by Vetiver extract. Composition analysis suggested that the sesquiterpene, khusimol, might contribute to the bactericidal activity of the Vetiver extract.

Antibacterial Effect of Essential Oils (Clove Oil, Castor Oil and Ginger Oil) Against Human Pathogenic Bacteria

Essential oils are volatile, natural, complex compounds which are produced as secondary metabolites by plants for their protection against various microorganisms as well as pests. A wide range of plants have been explored for their essential oils in the past few decades. The study was conducted to determine the antibacterial activity of essential oils against human pathogenic bacteria which were gram positive (Staphylococcus aureus and Streptococcus pyogenes) as well as gram negative (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Shigella sonnei). Five ml of three different oils, i.e. clove oil, castor oil, and ginger oil, were taken in a test tube so that each oil had four different concentrations. Four concentrations of (0, 25, 50 and 75) μL of oils were mixed with 1000, 975, 950 and 925 μL of DMSO respectively to make it a volume of 1ml. It was observed that clove oil was effective against the entire gram positive as well as gram negative bacteria that were used. The inhibition zone was greatest in the case of clove oil at 75 μL against P. aeruginosa (23 mm) and the smallest zone of inhibition was shown by castor oil against K. pneumoniae (12 mm). Other oils were sensitive as well as resistant to the bacteria. Hence, it is found that different oils have shown inhibitory activity towards different pathogens to a variable extent. However, clove oil was inhibitory to all the bacteria in all concentrations. Int. J. Appl. Sci. Biotechnol. Vol 9(4): 250-255

Comparative study on the phytochemical composition and antibacterial activity of the essential oil of Diphasia klaineana stems at pre-flowering and fruit set

The phytochemical composition and antibacterial activity of the essential oils of Diphasia klaineana at different developmental stages (pre-flowering and fruit set) were reported. The essential oils were extracted by continuous hydro distillation and their antibacterial activities were tested against Staphyloccocus aureus ATCC 25923. The yield of oil (w/w %) of stems in different stages was in the order: pre-flowering (0.21 %) &gt; fruit set (0.07 %). GC and GC/MS were analyzed the essential oils composition. In total, 35 and 34 constituents were identified and quantified in the mentioned samples, respectively. Monoterpene hydrocarbons were the main group of compounds in the stems during preflowering (42.40 %) and fruit set (56.15 %). Major compounds at pre-flowering were β-elemol, sabinene, guaiol and terpinen-4-ol. The antibacterial effect of essential oils was estimated by the disk diffusion method using Müller–Hinton agar and the measurement of diameters of inhibition zones. The bioassay results showed some variations between the two tested oils in their inhibitory activity against the tested bacteria at 10 µL. The essential oils from Diphasia klaineana stems at pre-flowering exhibited potent antibacterial activity against Staphyloccocus aureus ATCC 25923, with a minimum inhibitory concentration (MIC) value of 25 mg/mL, while the stems essential oil at fruit set had no activity.