New Insight into the Chemical Composition, Antimicrobial and Synergistic Effects of the Moroccan Endemic Thymus atlanticus (Ball) Roussine Essential Oil in Combination with Conventional Antibiotics

Thymus atlanticus: A Source of Nutrients with Numerous Health Benefits and Important Therapeutic Potential for Age-Related Diseases

Thymus atlanticus (Lamiaceae) is a plant endemic to the Mediterranean basin that is found in significant quantities in the arid regions of Morocco. Thymus atlanticus is used in traditional medicine to treat infectious and non-infectious diseases. It is also used for the isolation of essential oils and for the seasoning of many dishes in the Mediterranean diet. The major constituents of Thymus atlanticus are saponins, flavonoids, tannins, alkaloids, various simple and hydroxycinnamic phenolic compounds, and terpene compounds. Several of these compounds act on signaling pathways of oxidative stress, inflammation, and blood sugar, which are parameters often dysregulated during aging. Due to its physiochemical characteristics and biological activities, Thymus atlanticus could be used for the prevention and/or treatment of age-related diseases. These different aspects are treated in the present review, and we focused on phytochemistry and major age-related diseases: dyslipidemia, cardiovascular diseases, and type 2 diabetes.

Flowering phenophases influence the antibacterial and anti-biofilm effects of Thymus vulgaris L. essential oil

BACKGROUND

Essential oils are becoming increasingly popular in medicinal applications because of their antimicrobial effect. Thymus vulgaris L. (Lamiaceae) is a well-known and widely cultivated medicinal plant, which is used as a remedy for cold, cough and gastrointestinal symptoms. Essential oil content of thyme is responsible for its antimicrobial activity, however, it has been reported that the chemical composition of essential oils influences its biological activity. In order to explore flowering phenophases influence on the chemical composition of thyme essential oil and its antibacterial and anti-biofilm activity, plant materials were collected at the beginning of flowering, in full bloom and at the end of flowering periods in 2019.

METHODS

Essential oils from fresh and dried plant materials were distilled and analyzed with gas chromatography-mass spectrometry (GC-MS) and gas chromatography-flame ionization detection (GC-FID). The antibacterial activity was performed by broth microdilution and thin layer chromatography-direct bioautography (TLC-DB) assays and the anti-biofilm effect by crystal violet assay, respectively. Scanning electron microscopy was applied to illustrate the cellular changes of bacterial cells after essential oil treatment.

RESULTS

Thymol (52.33-62.46%) was the main component in the thyme essential oils. Thyme oil distilled from fresh plant material and collected at the beginning of flowering period exerted the highest antibacterial and anti-biofilm activity against Haemophilus influenzae, H. parainfluenzae and Pseudomonas aeruginosa.

CONCLUSION

The different flowering periods of Thymus vulgaris influence the antibacterial and anti-biofilm activity of its essential oils, therefore, the collection time has to be taken into consideration and not only the full bloom, but the beginning of flowering period may provide biological active thyme essential oil.

Antimicrobial and Antioxidant Properties of Natural Postbiotics Derived from Five Lactic Acid Bacteria

Background: The application of natural antimicrobial and antioxidant agents in food and pharmaceutical products has recently become a trend due to the high demand for them from consumers. Postbiotics are bioactive compounds that are produced when the healthy bacteria in the gut ferment fiber. Objectives: This study aimed to compare the antibacterial and antioxidant properties of postbiotics from 5 different lactic acid bacteria (LAB) including Lactiplantibacillus fermentum, Lactiplantibacillus plantarum, Lactiplantibacillus rhamnosus, Lactobacillus casei, and Lactobacillus acidophilus. Methods: Two different methods were adopted to obtain postbiotics (M1 and M2). M1 was the simple method in which the centrifugation was employed while in M2 method, ethyl acetate was used to obtain postbiotics. Agar disc diffusion, minimum inhibition concentration, and minimum bactericidal concentration were used to assess the antimicrobial activity of postbiotics. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) test was performed in order for investigating the antioxidant property. Results: The best results were recorded for L. casei compared to other LABs. Highest values of the agar disc diffusion method were obtained for L. casei. The inhibition zones for Salmonella enterica, Listeria monocytogenes, and Staphylococcus aureus, for examples, were 22 mm, 20 mm, and 19 mm, respectively. The postbiotic of L. casei also exhibited the most potent antioxidant activity among other probiotic bacteria. The data showed that M2 was a more effective method than the other method for acquiring postbiotics. Conclusions: It was recommended LABs postbiotics should be applied as antioxidant, antimicrobial, and preservatives in food and pharmaceutical industries due to their desired effects and natural characteristics.

Effects of Natural Borneol on Germ Tube Formation and Preformed Biofilm Activity in Candida albicans

Candida albicans infection mainly occurs in patients with suppressed immune function and is the main pathogen of nosocomial infections. The use of natural products aimed at controlling fungal diseases is considered an interesting alternative to synthetic fungicides due to their lower adverse reactions and the lower cost of plant preparations compared to modern conventional pharmaceuticals. Natural borneol has a long history of treating ulcers and local infections in traditional Chinese medicine. In this study, we present an analysis of the in vitro effects of natural borneol on planktonic cells of C albicans in the liquid and vapor phases. We also investigated the effects of natural borneol on germ tube formation and mature biofilm activity of C albicans. We found that vapor-phase borneol (minimum inhibitory concentration [MIC] 0.4 mg/cm3) inhibited C albicans more effectively than in the liquid phase (MIC 2 mg/mL). The C albicans germ tube decreased by 99% to 60% at sub-MICs of 0.5 to 0.125 mg/mL. The inhibitory effects of 0.25, 0.5, 1, 2, and 4 mg/mL borneol on the biofilm activity were 33.7%, 48.6%, 49.9%, 52.9%, and 58.2%, respectively. Natural borneol may have potential in the treatment and prevention of C albicans infections.

Synergistic Action of AMX Associated with 1,8-Cineole and Its Effect on the ESBL Enzymatic Resistance Mechanism

The purpose of the present study is twofold. First, it aims to evaluate the synergistic action of the ß-lactam antibiotic; AMX is associated with 1,8-cineole on six clinical isolates of ESBL-producing Escherichia coli and Klebsiella pneumoniae strains. Second, it aims to determine the effect this association has on the ESBL enzymatic resistance mechanism. The synergistic action of AMX/1,8-cineole was evaluated using partial inhibitory concentrations (PIC), determined by a microplate, a checkerboard and time-kill assays. The effect of AMX/1,8-cineole associations on the ESBL enzymatic resistance mechanism was evaluated using a new optimized enzymatic assay. This assay was based on the determination of the AMX antibacterial activity when combined with 1,8-cineole (at subinhibitory concentrations) in the presence or absence of the ß-lactamase enzyme toward a sensitive E. coli strain. The results of both checkerboard and time-kill assays showed a strong synergistic action between AMX and 1,8-cineole. The results of the enzymatic assay showed that the combination of AMX with 1,8-cineole notably influences the enzymatic resistance of the reaction by decreasing the affinity of the β-lactam antibiotic, AMX, to the β-lactamase enzyme. All obtained results suggested that the AMX/1,8-cineole association could be employed in therapy to overcome bacterial resistance to AMX while reducing the prevalence of resistance.

Synergistic effects of carvacrol, α-terpinene, γ-terpinene, ρ-cymene and linalool against Gardnerella species

Bacterial vaginosis (BV) is the most common vaginal infection affecting women worldwide. This infection is characterized by the loss of the dominant Lactobacillus community in the vaginal microbiota and an increase of anaerobic bacteria, that leads to the formation of a polymicrobial biofilm, mostly composed of Gardnerella spp. Treatment of BV is normally performed using broad-spectrum antibiotics, such as metronidazole and clindamycin. However, the high levels of recurrence of infection after treatment cessation have led to a demand for new therapeutic alternatives. Thymbra capitata essential oils (EOs) are known to have a wide spectrum of biological properties, including antibacterial activity. Thus, herein, we characterized two EOs of T. capitata and tested their antimicrobial activity as well as some of their main components, aiming to assess possible synergistic effects. Our findings showed that carvacrol and ρ-cymene established a strong synergistic antimicrobial effect against planktonic cultures of Gardnerella spp. On biofilm, carvacrol and linalool at sub-MIC concentrations proved more efficient in eliminating biofilm cells, while showing no cytotoxicity observed in a reconstituted human vaginal epithelium. The antibiofilm potential of the EOs and compounds was highlighted by the fact cells were not able to recover culturability after exposure to fresh medium.

Nanoparticles—Attractive Carriers of Antimicrobial Essential Oils

Microbial pathogens are the most prevalent cause of chronic infections and fatalities around the world. Antimicrobial agents including antibiotics have been frequently utilized in the treatment of infections due to their exceptional outcomes. However, their widespread use has resulted in the emergence of multidrug-resistant strains of bacteria, fungi, viruses, and parasites. Furthermore, due to inherent resistance to antimicrobial drugs and the host defence system, the advent of new infectious diseases, chronic infections, and the occurrence of biofilms pose a tougher challenge to the current treatment line. Essential oils (EOs) and their biologically and structurally diverse constituents provide a distinctive, inexhaustible, and novel source of antibacterial, antiviral, antifungal, and antiparasitic agents. However, due to their volatile nature, chemical susceptibility, and poor solubility, their development as antimicrobials is limited. Nanoparticles composed of biodegradable polymeric and inorganic materials have been studied extensively to overcome these limitations. Nanoparticles are being investigated as nanocarriers for antimicrobial delivery, antimicrobial coatings for food products, implantable devices, and medicinal materials in dressings and packaging materials due to their intrinsic capacity to overcome microbial resistance. Essential oil-loaded nanoparticles may offer the potential benefits of synergism in antimicrobial activity, high loading capacity, increased solubility, decreased volatility, chemical stability, and enhancement of the bioavailability and shelf life of EOs and their constituents. This review focuses on the potentiation of the antimicrobial activity of essential oils and their constituents in nanoparticulate delivery systems for a wide range of applications, such as food preservation, packaging, and alternative treatments for infectious diseases.

The Enhancement of the Photodynamic Therapy and Ciprofloxacin Activity against Uropathogenic Escherichia coli Strains by Polypodium vulgare Rhizome Aqueous Extract

Antibiotic therapy and photodynamic therapy (PDT) are commonly used to treat bacterial infections. Unfortunately, these methods are often ineffective. Therefore, agents that could effectively support antibiotic therapy and PDT in the inactivation of pathogens are being sought. Phytotherapy seems to be a good solution. The aim of the current research was to examine whether Polypodium vulgare extract (PvE) would improve the effectiveness of PDT and ciprofloxacin (CIP), an antibiotic that is commonly used to treat urinary tract infections in humans. UHPLC-MS analysis was performed to establish the PvE content. Chlorin e6 has been used as a photosensitizer in the PDT method. Biofilm production was established using the spectrophotometric method. The live cell count in planktonic and biofilm consortia was determined with the microdilution method and DAPI staining. The decrease of the bacterial survival, biofilm mass synthesis, and morphological changes of the bacteria under the combined treatments: PDT+PvE and CIP+PvE was noted. The results clearly indicate that the PvE can be used as a good agent for improving the efficacy of both PDT and the CIP activity to inactivate uropathogenic Escherichia coli strains. The obtained results are of particular value in the era of widespread and still-increasing drug resistance among bacterial pathogens.