Antibiofilm Activity Of Essential Oil Research Articles

Chemical composition, antimicrobial and antibiofilm activities of essential oil from Turkish endemic Prangos hulusii fruits

ABSTRACT The chemical composition, antimicrobial, and antibiofilm activities of the essential oil from the fruits of Turkish endemic Prangos hulusii were studied. Essential oil was analyzed by GC and GC/MS. Thirty-nine compounds were identified, which represent 98.6% of the total composition of the essential oil. Monoterpene hydrocarbons and sesquiterpene hydrocarbons were the most represented classes of volatiles with 49.8% and 21.0%, respectively. The main constituents of the essential oil were (E)-methyl cinnamate (22.9%), α-phellandrene (13.8%), and (E)-β-ocimene (12.9%). (E)-methyl cinnamate was detected in Prangos spp. for the first time. Antimicrobial activities against three Gram-positive bacteria, three Gram-negative bacteria, and three yeast strains were evaluated using disk diffusion test and microdilution method. Antibiofilm experiments were done by spectrophotometric microplate method and the results of Staphylococcus aureus, Escherichia coli, and Candida albicans were visualized via scanning electron microscopy. The essential oil had an antimicrobial effect and showed an antibiofilm effect on these strains.

Chemical composition, antioxidant, antimicrobial and antibiofilm activities of essential oil from the Moroccan endemic Plant, Calendula maroccana (Ball) B. D. Jacks.

The chemical characterization of the essential oil of the endemic Moroccan species, Calendula maroccana, was achieved by GC and GC-MS methods. The antioxidant, antimicrobial and antibiofilm activities of this essential oil were also studied. Eighty-one compounds were identified in the essential oil, representing 94.82% of the total. Sesquiterpenes predominate in the essential oil; 2-Methoxy-4-vinylphenol (16.13%), δ-amorphene (13.56%), α-cedrene (6.23%), γ-curcumene (5.10%) and α-bisabolol (4.94%) were the main constituents. The antioxidant potential was evaluated by DPPH, FRAP and ABTS assays: the essential oil exhibited antioxidant effectiveness with IC50 values of 0.92, 0.3 and 1.7 mg/mL, respectively. Moreover, the essential oil showed potent antimicrobial activity as revealed by inhibition zone values against selected clinically important pathogenic microorganisms. Inhibition zone values of 15.33 ± 0.19, 23 ± 0.05 and 15.33 ± 0.33 mm were observed against Staphylococcus aureus, Candida albicans and C. tropicalis, respectively. The maximal and minimal inhibition concentration values were in the range of 0.25 ± 0.17 - 4.68 ± 0.10 mg/mL for bacteria and 0.06 ± 0.03 - 0.12 ± 0.14 mg/mL, for Candida. The essential oil showed potent anti-biofilm activity with dual actions, inhibiting (69 - 88%) and eradicating (75 - 92%) the biofilms formed by the three tested bacteria strains. Based on these results, this essential oil can be considered as a natural antioxidant, antibacterial and antibiofilm agent that could be applied in phytotherapy, pharmaceutical and food sectors.

Anti-biofilm activity of essential oils in fruit and vegetable: A systematic review

Biofilm formation is one of the most serious threats in the food industry, mostly due to its contribution to the survival of spoiling and pathogenic microorganisms. Essential oils (EOs) are classified as secondary metabolites of plants which are generally recognized as safe (GRAS) and are typically mixtures of numerous components, and the monoterpenes constitute about 90% of their composition. The worldwide increase in foodborne outbreaks associated with fresh produce made us conduct a systematic review on in vitro application of EOs to remove biofilms in fruit and vegetables. Databases such as Scopus, PubMed and Web of Science were probed for relevant studies. The search criteria was restricted to published papers in English language up to August 2022. A total of 299 studies were extracted and after removing irrelevant papers, 17 papers were included in this review. Results indicated the effectiveness of EOs and their exposure time with fresh products on the breakdown of biofilms. Among the findings, only a part of a study indicated no effect of EOs (Citrus sinensis, Citrus aurantifolia, Coffea arabica and Vitex agnus-castus) against Erwinia amylovora biofilms in pear. Moreover, EOs were shown to act as pesticides and were reported to be effective against biofilm formation at pre-harvest stages. Most of the studied EOs showed strong effect on reducing bacterial burden without affecting the sensory score of fruits and vegetables; however, it is suggested that more attention should be paid to sensory evaluation of treated samples in future studies. These data underline the need for conducting more research on novel essential oils (or combinations) and characterization of them as natural antibiofilm agent.

Chemical composition, antibacterial and antibiofilm activities of essential oil from Tunisian Ephedra alata aerial parts

Chemical composition, antibacterial and antibiofilm activities of essential oil from Tunisian Ephedra alata aerial parts

Metabolomic Analysis of the Effect of Lippia origanoides Essential Oil on the Inhibition of Quorum Sensing in Chromobacterium violaceum.

Bacteria can communicate through quorum sensing, allowing them to develop different survival or virulence traits that lead to increased bacterial resistance against conventional antibiotic therapy. Here, fifteen essential oils (EOs) were investigated for their antimicrobial and anti-quorum-sensing activities using Chromobacterium violaceum CV026 as a model. All EOs were isolated from plant material via hydrodistillation and analyzed using GC/MS. In vitro antimicrobial activity was determined using the microdilution technique. Subinhibitory concentrations were used to determine anti-quorum-sensing activity by inhibition of violacein production. Finally, a possible mechanism of action for most bioactive EOs was determined using a metabolomic approach. Among the EOs evaluated, the EO from Lippia origanoides exhibited antimicrobial and anti-quorum activities at 0.37 and 0.15 mg/mL, respectively. Based on the experimental results, the antibiofilm activity of EO can be attributed to the blockage of tryptophan metabolism in the metabolic pathway of violacein synthesis. The metabolomic analyses made it possible to see effects mainly at the levels of tryptophan metabolism, nucleotide biosynthesis, arginine metabolism and vitamin biosynthesis. This allows us to highlight the EO of L. origanoides as a promising candidate for further studies in the design of antimicrobial compounds against bacterial resistance.

The Assessment of Antimicrobial and Anti-Biofilm Activity of Essential Oils against Staphylococcus aureus Strains.

The increase in antimicrobial resistance and tolerance over the years has become a serious public health problem, leading to the inevitable development of alternative antimicrobial agents as substitutes for industrial pharmaceutical antibiotics targeting humans and animals under the concept of one health. Essential oils (EOs) extracted from aromatic and pharmaceutical plants incorporate several bioactive compounds (phytochemicals) that positively affect human and animal health. Herein, this work aimed to examine a standardized chemical composition and screen the antimicrobial and anti-biofilm activity of Thymus sibthorpii, Origanum vulgare, Salvia fruticosa, and Crithmum maritimum EOs against three different Staphylococcus aureus strains by gold-standard disc diffusion, broth microdilution, and microtiter plate biofilm assays. Therefore, the evaluation of the above-mentioned EOs were considered as substitutes for antibiotics to combat the ever-mounting antimicrobial resistance problem. The observed bacterial growth inhibition varied significantly depending on the type and concentration of the antimicrobials. Thymus sibthorpii was determined as the strongest antimicrobial, with 0.091 mg/mL minimum inhibitory concentration (MIC) and a 14-33 mm diameter inhibition zone at 5% (v/v) concentration. All tested EOs indicated almost 95% inhibition of biofilm formation at their half MIC, while gentamicin sulfate did not show sufficient anti-biofilm activity. None of the methicillin-resistant strains showed resistance to the EOs compared to methicillin-sensitive strains. Thymus sibthorpii and Origanum vulgare could be potential alternatives as antimicrobial agents to overcome the problem of microbial resistance. The tested EOs might be incorporated into antimicrobial products as safe and potent antimicrobial and anti-biofilm agents.

Antibacterial and antibiofilm activity of essential oil of clove against Listeria monocytogenes and Salmonella Enteritidis.

The antibacterial and antibiofilm activity of essential oil of clove against Listeria monocytogenes and Salmonella Enteritidis were investigated. The chemical composition of the oil was characterized by gas chromatography-mass spectrometry. Stock solution of the essential oil of clove was prepared in 95% (v/v) ethanol (EOC). The antibacterial assays were performed by disk diffusion assay and minimal inhibitory concentration (MIC). The biomass of adhered cells and preformed biofilms after incubation with different concentrations of EOC was assessed by crystal violet. Eugenol was the major bioactive compound of clove essential oil, accounting for 78.85% of the total composition. The MIC values for L. monocytogenes and S. Enteritidis were 0.05 mg/ml and 0.1 mg/ml, respectively. The initial cell adhesion at MIC was inhibited by 61.8% for L. monocytogenes and 49.8% for S. Enteritidis. However, the effect of EOC was less marked on biofilm eradication than on cell adhesion. At MIC and within 1 hour of incubation with the EOC, the preformed biofilms were reduced by 30.2% and 20.3% for L. monocytogenes and S. Enteritidis, respectively. These results suggest that sanitizers based on clove essential oil could be a potential strategy to control biofilms in food-related environments.

Contribution of Essential Oils to the Fight against Microbial Biofilms—A Review

The increasing clinical use of artificial medical devices raises the issue of microbial contamination, which is a risk factor for the occurrence of biofilm-associated infections. A huge amount of scientific data highlights the promising potential of essential oils (EOs) to be used for the development of novel antibiofilm strategies. We aimed to review the relevant literature indexed in PubMed and Embase and to identify the recent directions in the field of EOs, as a new modality to eradicate microbial biofilms. We paid special attention to studies that explain the mechanisms of the microbicidal and antibiofilm activity of EOs, as well as their synergism with other antimicrobials. The EOs are difficult to test for their antimicrobial activity due to lipophilicity and volatility, so we have presented recent methods that facilitate these tests. There are presented the applications of EOs in chronic wounds and biofilm-mediated infection treatment, in the food industry and as air disinfectants. This analysis concludes that EOs are a source of antimicrobial agents that should not be neglected and that will probably provide new anti-infective therapeutic agents.

In vitro and in vivo evaluation of antibacterial and anti-biofilm properties of five ethnomedicinal plants against oral bacteria by TEM.

The aim of the present study was to investigate antibacterial and antibiofilm activity of a few medicinal plants against oral bacteria. Salvia officinalis, Lippie citriodora, Mentha piperita, Echinacea purpurea and Matricaria chamomilla were extracted. Isolates from oral cavity were identified by microbiological and molecular methods. Minimum inhibitory concentration and minimum bactericidal concentration were determined by Broth microdilution method. The anti-biofilm activity of essential oils and extracts investigated and as a mixture by Broth dilution method. Toxicity of the herbal mixture was assayed by in Wistar rats treated with intradermal injection. Wound healing properties of the herbal mixture against infected wounds on the back of the rats were investigated. Anti-biofilm activity was investigated on tooth surfaces. Bacterial structure changes and fine- structure study were performed by light microscopy and Transmission electron microscopy. The lowest MIC and MBC for the plant mixtures was 0.0002 mg/ml belonged to Streptococcus pyogenes and the highest values (0.025 mg/ml) belonged to Eikenella corrodens. The essential oils of S.officinalis, L.citriodora and M.piperita, but not E.purpurea and M.chamomilla extracts, were able to remove the biofilms created by the studied bacteria. The herbal mixture was able to completely heal the wound skin of rats in 21 days (p<0.05 compared to control). The mixture was able to decompose the teeth biofilm in 45 seconds. The results of light and electron microscopy showed that the bacterial structure exposed to the herbal mixture was deformed. It was concluded that the essential oils of S.officinalis, L.citriodora and M.piperita had significant effects on inhibition of oral bacteria biofilm formation.

Antibacterial and antibiofilm activity of essential oil of Achillea biebersteinii and its mode of action

Context: Microbial biofilms and antibiotic-resistant bacterial strains pose a challenge in clinical world as they fail to respond to conventional treatments. This failure of antibiotic treatment led researchers to look for alternatives. A possible alternative is plants derived essential oils. Many studies have reported that certain essential oils succeed where antibiotics fail. Aims: To test antibacterial and antibiofilm activities of essential oil of Achillea biebersteinii and its mode of action. Methods: Minimum biofilm inhibitory concentration (MBIC) susceptibility assays were performed using a biofilm inoculator with a 96-well plate with peg led. Minimum inhibitory concentration (MIC) was determined in normal microtitre plates using a twofold dilution series. Results: Achillea biebersteinii essential oil showed good activity against all tested bacteria. The MIC values were in the range of 0.125 - 1 mg/mL while MBIC values were in the range of 0.125 – 4 mg/mL. The mechanism of action of Achillea biebersteinii essential oil is related to a strong increase in membrane permeability of 260 nm absorbing materials and potassium ions from the cell membrane. Achillea biebersteinii essential oil was able to inhibit initial adherence of methicillin-resistant Staphylococcus aureus (ATCC 43300) at sub-inhibitory concentrations. Conclusions: Achillea biebersteinii essential oil has the potential for use as an effective antibacterial and antibiofilm agent that functions by impairing cell membrane permeability resulting in cellular death.

Chemical composition and anti-biofilm activity of essential oil from Citrus medica L. var. sarcodactylis Swingle against Listeria monocytogenes

Listeria monocytogenes is an important foodborne pathogen that could cause listeriosis and poses potential threats to human health. Citrus medica L. var. sarcodactylis Swingle, also known as Fingered Citron, is a citrus species widely cultivated in South China. The aim of this work was to investigate the anti-biofilm efficacy of essential oil from Fingered Citron (FCEO) against L. monocytogenes. The crystal violet assay showed that FCEO exhibited strong anti-biofilm activity on both inhibiting biofilm formation and eradicating preformed biofilm. XTT assay indicated that FCEO significantly increased the metabolic active cells in the biofilm. Confocal scanning laser microscopy images and COMSTAT assay revealed that FCEO destroyed the intact architecture of biofilm, reduced biofilm biomass, thickness and substratum coverage. The morphological changes of cells in the biofilm were observed by scanning electron microscopy, which showed that FCEO could cause the wrinkle, collapse, lysis and cytoplasmic content leakage of cells. Our results also indicated that FCEO displayed its anti-biofilm activity through both biofilm dispersal and cell killing. Our findings provide evidence that FCEO exhibits strong anti-biofilm activity and might be used as a potential agent to control L. monocytogenes biofilm.

Antimicrobial and Antibiofilm Activity of Essential Oil of Cymbopogon citratus against Oral Microflora Associated with Dental Plaque

Aims: Dental biofilms are complex, multi-species microorganism communities that inhabit the oral cavity in the form of dental plaque which causes dental caries and periodontal diseases. The present study aims to explore the potential of Lemon Grass Essential Oil (LGEO) extracted from Cymbopogon citratus as antimicrobial and antibiofilm agent against the microorganisms responsible for dental plaque.&#x0D; Study Design: Observational and comparison study.&#x0D; Place and Duration of Study: Research centre, Department of Microbiology, Abasaheb Garware college, Pune, India, between Dec 2012 to Jan 2017.&#x0D; Methodology: Three bacterial species primarily responsible for the biofilm formation were isolated from dental plaque and identified using 16S ribosomal RNA sequences. Five most primary colonizer of dental plaque organisms were acquired from the Microbial Type Culture Collection cultures. Antimicrobial as well as antibiofilm activity of LGEO, was determined against these eight biofilm forming microorganism. The antibiofilm activity of LGEO was evaluated against oral flora individually, as well as in consortium.&#x0D; Results: LGEO displayed excellent antimicrobial activity against eight test organisms associated with dental plaque, representing four genera namely Streptococcus, Staphylococcus, Lactobacillus and Candida. MIC of LGEO for all test organisms was determined as 1.5% (v/v). The LGEO was found to exhibit as high as 76% biofilm inhibitory activity even in the consortium, where the biofilm formation sometimes has been noted to be comparatively more than that of the individual organism, making LGEO a very promising antibiofilm agent.&#x0D; Conclusion: LGEO present in rampantly grown plant, Cymbopogon citratus, has remarkable antimicrobial and antibiofilm activity against the dental plaque organism and thus can be the economical, convenient, natural and nontoxic herbal material to effectively control the oral microflora associated with dental plaque.

Effect of simultaneous ultrasonic and microwave assisted hydrodistillation on the yield, composition, antibacterial and antibiofilm activity of essential oils from Citrus medica L. var. sarcodactylis

Simultaneous ultrasonic/microwave assisted hydrodistillation extraction (UMHE) was first employed to extract essential oil. Meanwhile, the effects of UMHE, hydrodistillation extraction (HE), microwave assisted hydrodistillation extraction (MHE) and solvent extraction (SE) on the yield, chemical composition, antibacterial and antibiofilm activity of essential oil were evaluated. The optimized conditions determined by response surface methodology were as follows: solvent to solid ratio was 5.2:1 (ml/g), extraction time was 15.5 min, and microwave power was 816 W. Moreover, 15 min was sufficient for UMHE to obtain higher yield than that by HE for 1.5 h, indicating a significant reduction of extraction time and an improvement of efficiency. Forty five compounds were identified in the essential oil through GC-MS analysis. The composition of essential oils obtained by UMHE, MHE and HE was similar, and the major compounds were D-Limonene, γ-Terpinene and α-Pinene. Moreover, the results indicated that the antibacterial activity of the essential oils was similar. All the essential oils exhibited inhibitive effect on biofilm formation. The inhibitive effect of essential oils of HE and UMHE was significantly higher than that of the essential oil obtained by SE. This study suggests that UMHE is a rapid and efficient alternative for the extraction of essential oils, with a nice potential for application. Also, UMHE provides a possible approach to improve the antibacterial and antibiofilm activity of essential oils.

Streptococcus pneumoniae quorum sensing and biofilm formation are affected by Thymus daenensis, Satureja hortensis, and Origanum vulgare essential oils.

The aim of this study was to investigate the effect of Thymus daenensis L., Satureja hortensis L., and Origanum vulgare L. essential oils (EOs) on the planktonic growth, biofilm formation, quorum sensing (QS), and competence system (CS) of Streptococcus pneumoniae. The anti-biofilm activity of EOs was determined by Microtiter-Plate Test (MtP) and scanning electron microscope (SEM). The QS and CS inhibitory activities were determined on the pre-grown biofilm by gene expression analysis using quantitative real-time RT-PCR. Using gas chromatography-mass spectrometry analysis, the major components of the tested EOs were detected. The MtP and SEM detected a significant inhibitory effect of the three EOs on biofilm formation at sub-minimum inhibitory concentrations (MICs). The most anti-biofilm activity was seen for T. daenensis. LuxS and pfs genes (genes involved in QS) downregulated the following treatment with MIC/2 of Thymus and Satureja EOs. Thymol, carvacrol, p-cymene, pulegone, and 1,8-cineole were the major components of the tested EOs. The used EOs seem to be good candidates for preventing biofilm formation and subsequent colonization of S. pneumoniae. This study introduced T. daenensis and S. hortensis as new anti-biofilm and QS inhibitor agents with a natural origin.

In Vitro Evaluation of Antimicrobial and Antibiofilm Potentials of Essential Oil of Tanacetum argenteum (Lam.) Willd. subsp. canum (K.Koch) Grierson var. canum

This study was performed to determine the antimicrobial and antibiofilm activities of essential oil of Tanacetum argenteum (Lam.) Willd . subsp . canum (K.Koch) Grierson var . canum . The plant was collected from Amasya. The antimicrobial activity was determined by disc diffusion and microdilution broth methods. Essential oil was active against indicator organisms. The maximal inhibition zone diameter were as follows: E. cloacae ATCC 28355 (14mm), P. fluorescens ATCC 55241 (16mm), P. aeruginosa ATCC 27853 (19mm), S. sonnei RSKK 8177 (18mm), E. coli ATCC 25922 (21mm), E. coli O157:H7 (13mm), Y. enterocolitica RSKK 1501 (11mm), C. jejuni ATCC 33291 (12mm), K. pneumoniae ATCC 27736 (13mm), S. enteritidis RSKK 171 (12mm), S. aureus ATCC 33862 (26mm) and S. aureus ATCC 25923 (29mm), M. luteus NRLL-B-4375 (20mm), E. faecalis ATCC 19433 (19mm), B. cereus NRRL-B-3711 (30mm), B. cereus RSKK (32mm), C. albicans ATCC 10231 (19mm) and C. tropicalis (17mm). The minimum inhibitory concentration (MIC) and minimum lethal concentration (MLC) were ranged from 62.5-900 µg/ml and 125-1000 µg/ml, respectively. Plant essential oil was the most active against B. cereus NRRL-B 3711 and B. subtilis RSKK 867. Also, the essential oil has shown a strong anti-candidal activity against two Candida species. For determining the antibiofilm effect, various dilutions of oil were studied on M. luteus, E. cloacae, P. fluorescens, Y. enterocolitica and S. enteritidis by using microplate biofilm assay. According to results, antibiofilm effect was found as weak. Maximum antibiofilm effect was determined on E. cloacae ATCC 28355 with 32.92% biofilm inhibition rate.

The antioxidant, antibacterial, antibiofilm activity of essential oil from Citrus medica L. var. sarcodactylis and its nanoemulsion

In this work, the nanoemulsion of essential oil from Citrus medica L. var. sarcodactylis was prepared using a spontaneous emulsification method. Meanwhile, the effect of nanoemulsification on the antioxidant, antibacterial and antibiofilm activity of essential oil was evaluated. GC–MS analysis indicated nineteen compounds in the essential oil, and the essential oil was dominated by d-Limonene (50.04%). The minimum and stable droplets (73 nm) of essential oil nanoemulsion were formulated when the concentration of essential oil in oil phase was 50% (w/w). The hydroxyl radicals, DPPH radicals scavenging ability, iron reducing power, antibacterial and antibiofilm activity of nanoemulsified essential oil were significantly higher than those of pure essential oil at same concentration. Moreover, the nanoemulsified essential oil exhibited higher inhibitive effect on the bacteria in tofu than pure essential oil. Therefore, nanoemulsification significantly enhanced the antioxidant, antibacterial and antibiofilm activity/efficiency of essential oils, which will promote the abroad utilization of essential oils.

Antimicrobial and antibiofilm activity of Baccharis psiadioides essential oil against antibiotic-resistant Enterococcus faecalis strains

Context: Baccharis psiadioides (Less.) Joch. Müller (Asteraceae) is considered as a producer of bioactive essential oils and is used in south Brazilian folk medicine for its proprieties as stimulant, antipyretic, anti-inflammatory and as an antidote for snake bites.Objective: To verify the antimicrobial and antibiofilm activities of the essential oil of B. psiadioides (EOBP) against antibiotic-resistant Enterococcus faecalis.Materials and methods: The initial evaluation of EOBP activity was conducted by the agar and microdilution methods against 13 antibiotic-resistant E. faecalis strains. The antibiofilm effect was determined by the application of EOBP in the earlier adherent cells or to the stabilized biofilm for 24 h and was evaluated by crystal violet, viability and scanning electron microscopy (SEM) assays. Chemical composition of EOBP was determined by gas chromatography (GC/FID – GC/MS).Results: The MIC values for EOBP were at least 1.25% and 4–16% for agar and microdilution assays, respectively. The EOBP reduced the microbial adherence and the viability of the cells, but did not cause the complete disruption of biofilms. SEM images indicate that EOBP influences the adherence of cells to a surface. The monoterpene β-pinene was the major constituent identified in EOBP.Conclusion: This research shows the ability of EOBP to control resistant E. faecalis strains and to reduce the biofilm amount attached to abiotic surfaces, indicating its role as a promising new natural antimicrobial agent. Moreover, these results further contribute to the growing number of studies of plant natural products which suggest that these compounds can combat resistant microorganisms.

Anti-biofilm and antimicrobial activity of &lt;i&gt;Mentha pulegium&lt;/i&gt; L essential oil against multidrug-resistant &lt;i&gt;Acinetobacter baumannii&lt;/i&gt;

Purpose: To investigate the antimicrobial and anti-biofilm activities of essential oil from Mentha pulegieum L. (EOMP) on multi-drug resistant (MDR) isolates of A. baumannii, as well as its phytochemical composition, antioxidant properties and cytotoxic activity.Methods: The phytochemical composition of EOMP was analyzed by gas chromatography, while its antimicrobial activities were determined by disc diffusion and broth micro-dilution methods. Minimal biofilm inhibition concentration (MBIC) and minimal biofilm eradication concentration (MBEC) tests were used for assessment of its anti-biofilm properties. Viability in the biofilm was studied using 2,3-bis (2- methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) assay, while colorimetric assay was used to assess its cytotoxicity on L929 cellsResults: D-isomenthone, pulegone, isopulegone, menthol and piperitenone were the major components of the plant extract. EOMP produced &gt; 22 mm inhibition zone for the isolates, with minimum inhibitory concentration (MIC) and MBIC of 0.6 - 2.5 and 0.6 - 1.25 μL/mL, respectively, while MBEC was ≥ 10 μL/msL. EOMP damaged biofilm structures formed by A. baumannii strains at MIC by 26 – 91 %.Conclusion: These results suggest that EOMP contains agents that may be useful in the development of new drugs against A. baumannii infections.Keywords: Mentha pulegium, Essential oil, Anti-biofilm, Antimicrobial activity, Multi-drug resistance, A. baumannii

Anti-biofim and Antibacterial Effect of Essential Oils and Their Major Compounds

Essential oils are plant secondary metabolites commonly used in traditional medicine to treat infectious diseases. Along with their compounds, oils can contribute to development of new antimicrobial/antibiofilm products. Our study evaluated antibacterial activity of essential oils and their major compounds on Escherichia coli and Staphylococcus aureus planktonic cells and anti-biofilm activity. The effect of essential oils and their major compounds on biofilm and planktonic cells was assessed by quantifying the number of viable cells (CFU). Biomass quantification (absorbance = OD570nm) was also performed to evaluate anti-biofilm activity. Planktonic cells were more susceptible to the action of agents. Escherichia coli was reduced by 100% with cinnamon and palmarosa oil. The treatment showed an interesting anti-biofilm activity, whereas green tea essential oil and its major compound, terpinen-4-ol, yielded less effective results. Reduction of viable cells in biofilm biomass was significant. Although our research is one of the first experiments in anti-biofilm activity of essential oils and their compounds against Escherichia coli and Staphylococcus aureus, pharmacological data confirm that the materials used in the trial do not pose health risk. Thus, essential oils and their compounds can be safely used in research to identify new antibacterial and anti-biofilm products against pathogenic bacteria.

Antibiofilm activity of essential oils and plant extracts against Staphylococcus aureus and Escherichia coli biofilms

Bacterial biofilms pose health risks in clinical environments, food industry and drinking water systems. Here, we investigated in vitro antibiofilm activities of essential oils (EO) and plant extracts of peppermint (Mentha × piperita L.), coriander (Coriandrum sativum L.), and anise (Pimpinella anisum L.). Minimum inhibitory concentration assay (MIC) was carried out using two-fold serial dilution method and MTT assay against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. Biofilm growth and development were assessed using crystal violet (CV) and XTT reduction assays. Antibacterial activity was observed for almost all plant extracts and all EOs against both bacterial strains with stronger activity against S. aureus. All EOs (at MIC value of 0.8 to 0.63 μl/ml) and 8 out of 14 plant extracts (at MIC value of 2–4 mg/ml) inhibited bacteria cell attachment of both bacteria. CV and XTT reduction assay for the plant extracts and EOs with inhibition of bacteria attachment by at least 50%, demonstrated that coriander EO had the highest antibiofilm activity against biofilm formed by both tested bacteria (S. aureus and E. coli) at lowest MIC value 0.8 μl/ml and 1.6 μl/ml, respectively, indicating further investigations due to the oil's high antibiofilm activity potential.