Bactericidal activity of herbal volatile oil extracts against multidrug-resistant Acinetobacter baumannii

Evaluation of Cinnamon Essential Oil and Its Emulsion on Biofilm-Associated Components of Acinetobacter baumannii Clinical Strains

BACKGROUND/OBJECTIVES

Acinetobacter baumannii, one of the most dangerous pathogens, is able to form biofilm structures and aggravate its treatment. For that reason, new antibiofilm agents are in need, and new sources of antibiofilm compounds are being sought from plants and their products. Cinnamon essential oil is associated with a wide spectrum of biological activities, but with a further improvement of its physicochemical properties it could provide even better bioavailability. The aim of this work was the evaluation of the antibiofilm properties of cinnamon essential oil and its emulsion.

METHODS

In order to evaluate the antibiofilm activity, crystal violet assay was performed to determine biofilm biomass. The main components of the biofilm matrix were measured as well as the motile capacity of the tested strains. Gene expression was monitored with RT-qPCR, while treated biofilms were observed with Raman spectroscopy.

RESULTS

A particularly strong potential against pre-formed biofilm with a decreased biomass of up to 66% was found. The effect was monitored not only with regard to the whole biofilm biomass, but also on the individual components of the biofilm matrix such as exopolysaccharides, proteins, and eDNA molecules. Protein share drops in treated biofilms demonstrated the most consistency among strains and rose to 75%. The changes in strain motility and gene expressions were investigated after the treatments were carried out. Raman spectroscopy revealed the influence of the studied compounds on chemical bond types and the components present in the biofilm matrix of the tested strains.

CONCLUSIONS

The results obtained from this research are promising regarding cinnamon essential oil and its emulsion as potential antibiofilm agents, so further investigation of their activity is encouraged for their potential use in biomedical applications.

The antibacterial capabilities of alginate encapsulated lemon essential oil nanocapsules against multi-drug-resistant Acinetobacter baumannii

Controlling microbial pollutants is a significant public health concern as they cause several chronic microbial infections and illnesses. In recent years, essential oils (EOs) have become intriguing alternatives for synthetic antimicrobials due to their biodegradability, natural source extraction, and strong antibacterial properties. The bactericidal properties of alginate containing lemon essential oil were examined in this investigation. Following the screening of the MDR strains, the morphological properties of the produced nanoparticles were examined using SEM, DLS, and FTIR. Additionally, the durability, effectiveness, and drug dispersion of encapsulation were assessed. Bacterial virulence factor gene amounts were measured using Q-real-time PCR. Concurrently, the cytotoxic effect of the nanomaterials was evaluated using MTT techniques. Nanoparticles of lemon essential oil encapsulated in alginate, measuring 500 ± 19.32 nm in size, with entrapment efficiency of 77.73 ± 1.78% and were stable for 60 days at 4 °C. Alginate encapsulated with lemon essential oil nanoparticles (ALN) exhibited potent antibacterial qualities, according to the biological investigation. Their ability to decrease the transcription of bacterial virulence genes at least statistically significantly (P ≤ 0.05) served as evidence for this. Between 1.56 and 100 µg/mL (P ≤ 0.01), ALN exhibited lower cytotoxicity against CCD841CoN than free lemon essential oil. The findings show that ALN nanoparticles have the potential to be a breakthrough in the fight against highly resistant illnesses. ALN nanoparticles' potent antibacterial efficacy against MDR strains of Acinetobacter baumannii may inspire new directions in antibacterial research.

Polymyxin combined with Ocimum gratissimum essential oil: one alternative strategy for combating polymyxin-resistant Klebsiella pneumoniae

Introduction. Multidrug-resistant infections present a critical public health due to scarce treatment options and high mortality. Ocimum gratissimum L. essential oil (O.geo) is a natural resource rich in eugenol known for its antimicrobial activity.Hypothesis/Gap Statement. O.geo may exert effective antimicrobial activity against polymyxin-resistant Klebsiella pneumoniae and, when combined with Polymyxin B (PMB), may exhibit a synergistic effect, enhancing treatment efficacy and reducing antimicrobial resistance.Aim. This study aims to investigate the antimicrobial activity of O.geo against polymyxin-resistant K. pneumoniae using in vitro tests and an in vivo Caenorhabditis elegans model.Methodology. The O.geo was obtained by hydrodistillation followed by gas chromatography. The MIC and antibiofilm activity were determined using broth microdilution. Checkerboard and time-kill assays evaluated the combination of O.geo and polymyxin B (PMB), whereas a protein leakage assay verified its action.Results. Eugenol (39.67%) was a major constituent identified. The MIC of the O.geo alone ranged from 128 to 512 µg ml-1. The fractional inhibitory concentration index (0.28) and time-kill assay showed a synergism. In addition, O.geo and PMB inhibited biofilm formation and increased protein leakage in the plasma membrane. The treatment was tested in vivo using a Caenorhabditis elegans model, and significantly increased survival without toxicity was observed.Conclusion. O.geo could be used as a potential therapeutic alternative to combat infections caused by multidrug-resistant bacteria, especially in combination with PMB.

Antibacterial Activity and Proposed Mode of Action of Extracts from Selected Zimbabwean Medicinal Plants against Acinetobacter baumannii

Acinetobacter baumannii was identified by the WHO as a priority pathogen in which the research and development of new antibiotics is urgently needed. Plant phytochemicals have potential as sources of new antimicrobials. The objective of the study was to determine the antibacterial activity of extracts of selected Zimbabwean medicinal plants against A. baumannii and determine their possible mode of action. Extracts were prepared from the leaves of the eight plants including the bark of Erythrina abyssinica using solvents of different polarities. Antibacterial activity was evaluated using the microbroth dilution method coupled with the in vitro iodonitrotetrazolium colorimetric assay. The effect of the extracts on membrane integrity was determined by quantifying the amount of protein and nucleic acid leaked from the cells after exposure to the extracts. The effects of the extracts on biofilms were investigated. Toxicity studies were carried out using sheep erythrocytes and murine peritoneal cells. Seven out of eight evaluated plant extracts were found to have antibacterial activity. The Combretum apiculatum acetonie (CAA) extract showed the highest inhibitory activity against A. baumannii with a minimal inhibitory concentration of 125 µg/mL. The minimum inhibitory concentration (MIC) of the CAA extract caused a protein leakage of 32 µg/mL from A. baumannii. The Combretum apiculatum acetonie (CAA), C. apiculatum methanolic (CAM), Combretum zeyheri methanolic (CZM), and Erythrina abyssinica methanolic (EAM) extracts inhibited A. baumannii biofilm formation. The EAM extract was shown to disrupt mature biofilms. The potent extracts were nontoxic to sheep erythrocytes and mouse peritoneal cells. The activities shown by the extracts indicate that the plants have potential as sources of effective antibacterial and antibiofilm formation agents against A. baumannii.

Treatment and Management of Acinetobacter Pneumonia: Lessons Learned from Recent World Event

Acinetobacter pneumonia is a significant healthcare-associated infection that poses a considerable challenge to clinicians due to its multidrug-resistant nature. Recent world events, such as the COVID-19 pandemic, have highlighted the need for effective treatment and management strategies for Acinetobacter pneumonia. In this review, we discuss lessons learned from recent world events, particularly the COVID-19 pandemic, in the context of the treatment and management of Acinetobacter pneumonia. We performed an extensive literature review to uncover studies and information pertinent to the topic. The COVID-19 pandemic underscored the importance of infection control measures in healthcare settings, including proper hand hygiene, isolation protocols, and personal protective equipment use, to prevent the spread of multidrug-resistant pathogens like Acinetobacter. Additionally, the pandemic highlighted the crucial role of antimicrobial stewardship programs in optimizing antibiotic use and curbing the emergence of resistance. Advances in diagnostic techniques, such as rapid molecular testing, have also proven valuable in identifying Acinetobacter infections promptly. Furthermore, due to the limited availability of antibiotics for treating infections caused A. baumannii, alternative strategies are needed like the use of antimicrobial peptides, bacteriophages and their enzymes, nanoparticles, photodynamic and chelate therapy. Recent world events, particularly the COVID-19 pandemic, have provided valuable insights into the treatment and management of Acinetobacter pneumonia. These lessons emphasize the significance of infection control, antimicrobial stewardship, and early diagnostics in combating this challenging infection.

Synergistic Antibiofilm Action of Cinnamomum verum and Brazilian Green Propolis Hydroethanolic Extracts against Multidrug-Resistant Strains of Acinetobacter baumannii and Pseudomonas aeruginosa and Their Biocompatibility on Human Keratinocytes

The accumulated dental biofilm can be a source of oral bacteria that are aspirated into the lower respiratory tract causing ventilator-associated pneumonia in hospitalized patients. The aim of this study was to evaluate the synergistic antibiofilm action of the produced and phytochemically characterized extracts of Cinnamomum verum and Brazilian green propolis (BGP) hydroethanolic extracts against multidrug-resistant clinical strains of Acinetobacter baumannii and Pseudomonas aeruginosa, in addition to their biocompatibility on human keratinocyte cell lines (HaCaT). For this, High-performance liquid chromatography analysis of the plant extracts was performed; then the minimum inhibitory and minimum bactericidal concentrations of the extracts were determined; and antibiofilm activity was evaluated with MTT assay to prevent biofilm formation and to reduce the mature biofilms. The cytotoxicity of the extracts was verified using the MTT colorimetric test, evaluating the cellular enzymatic activity. The data were analyzed with one-way ANOVA and Tukey's tests as well as Kruskal-Wallis and Dunn's tests, considering a significance level of 5%. It was possible to identify the cinnamic aldehyde in C. verum and p-coumaric, caffeic, and caffeoylquinic acids as well as flavonoids such as kaempferol and kaempferide and Artepillin-C in BGP. The combined extracts were effective in preventing biofilm formation and reducing the mature biofilms of A. baumannii and P. aeruginosa. Moreover, both extracts were biocompatible in different concentrations. Therefore, C. verum and BGP hydroethanolic extracts have bactericidal and antibiofilm action against multidrug resistant strains of A. baumannii and P. aeruginosa. In addition, the combined extracts were capable of expressively inhibiting the formation of A. baumannii and P. aeruginosa biofilms (prophylactic effect) acting similarly to 0.12% chlorhexidine gluconate.

Enhanced activity of Ellagic acid in lipid nanoparticles (EA-liposomes) against Acinetobacter baumannii in immunosuppressed mice

Acinetobacter baumannii infections have come to the surface in huge numbers in the recent decades. Furthermore, A. baumannii has adopted great ability to nullify the majority of currently available antibiotics. With the purpose of finding a nontoxic and efficient therapeutic agent, we analyzed the activity of Ellagic acid (EA) against the multidrug-resistant A. baumannii. EA not only demonstrated its activity against A. baumannii, but also inhibited the biofilm formation. Since EA shows poor solubility in an aqueous environment, a lipid nanoparticle-based (liposomal) formulation of EA (EA-liposomes) was prepared and its effectiveness was assessed to treat bacterial infection in the immunocompromised murine model. Therapy with EA-liposomes imparted greater protection to infected mice by increasing the survival and decreasing the bacterial load in the lungs. A. baumannii infected mice treated with EA-liposomes (100 mg/kg) showed 60% survival rate as compared to 20% of those treated with free EA at the same dose. The bacterial load was found to be 32778 ± 12232 in the lungs of EA-liposomes (100 mg/kg)-treated mice, which was significantly lower to 165667 ± 53048 in the lung tissues of free EA treated mice. Likewise, EA-liposomes also restored the liver function (AST and ALT) and kidney function parameters (BUN and creatinine). The broncho-alveolar fluid (BALF) from infected mice contained greater quantities of IL-6, IL-1β and TNF-α, which were significantly alleviated in EA-liposomes treated mice. These findings together support the possible implication of EA-liposomes to treat A. baumannii infection, especially in immunocompromised mice.

Antimicrobial Efficacy of Essential Oils and Their Combination Against Microorganisms Associated With Postradiation Therapy in Patients With Head and Neck Cancer: An In Vitro Study

Background Head and neck cancer ranks as the sixth most common cancer globally. Reduced saliva production brought on by postradiation therapy upsets the delicate balance between bacterial load and a weakened immune system. Oral hygiene is commonly neglected in patients who have undergone radiotherapy and they often develop dry mouth, mucositis due to radiation therapy, etc., as side effects. Despite being a part of the current standard, chlorhexidine carries numerous disadvantages such as taste alteration, teeth staining, and dry mouth. An extensive review of the literature demonstrates the antibacterial properties of essential oils (EOs) derived from plant materials, which may be able to prevent the development of such opportunistic microorganisms in the oral cavity. Methodology The cinnamon bark EO and Cajeput EO were procured and checked for their solubility. The final ratio at which the oils were found to be soluble was the 1:1 (w/v) ratio. The minimum inhibitory concentration (MIC) of cinnamon bark oil (Cinnamomum verum) and Cajeput oil (Melaleuca leucadendron) against Staphylococcus aureus, Enterococcus faecalis, and Candida albicans was determined by serial dilution method using Resazurin dye, and the minimum bactericidal concentration (MBC) was done by a spread plating method. The polyherbal mouthwash was subjected to cytotoxicity assay against human gingival fibroblasts. All the experiments were performed in triplicates. Results The overall results showed that cinnamon bark EO had the strongest efficacy against S. aureus (0.33 ± 0.14 mg/mL) and E. faecalis (0.41 ± 0.14 mg/mL), but not against C. albicans (2.85 ± 2.11 mg/mL). Cajeput EO showed the least efficacy against all the groups; whereas the combination of EOs proved to be the most efficacious and showed good antimicrobial activity against these most commonly encountered microorganisms in head and neck cancer postradiotherapy. Conclusions Cinnamon and Cajeput EOs in combination proved to be effective in this in vitro study against the most common microorganisms encountered in patients with head and neck cancer postradiotherapy and are comparable to 0.2% chlorhexidine.

Cinnamon oil solid self-microemulsion mediates chronic mild stress-induced depression in mice by modulating monoamine neurotransmitters, corticosterone, inflammation cytokines, and intestinal flora

Cinnamon oil (CO) is a classic Chinese medicine with excellent soothing effects on exhaustion, weakness and depression. Cinnamaldehyde is the main active ingredient of cinnamic oil. Although CO have antidepression-like effects, limited information is available. Furthermore, the disadvantages of CO, such as low oral availability and difficult portability, limit its development. In this study, a Cinnamon Oil Solid Self-Microemulsifying Drug Delivery System (CO-S-SME) was designed, prepared. In addition, we explored the effects and mechanisms of CO-S-SME on chronic unpredictable mild stress (CUMS)-induced depression-like behavior, monoamine neurotransmitters, inflammatory factors, intestinal flora in mice. Mice were subjected CUMS to establish the depression model. The antidepressant effect of CO-S-SME was evaluated by behavioral tests. In addition, the expression levels of neurotransmitters, corticosterone (CORT) and inflammatory factors in CUMS mice were analyzed by enzyme-linked immunosorbent assay. In addition, we explored the effects of CO-S-SME on the diversity and richness of intestinal flora of mice in each group. Behavioral tests showed that CO-S-SME could effectively improve depression-like behaviors in CUMS mice. Specifically, CO-S-SME treatment effectively increased neurotransmitter levels and reduced the expressions of corticosterone and inflammatory factors in CUMS mice. CO-S-SME also changed the intestinal flora composition, decreased the ratio of Firmicutes to Bacteroidetes, reduced relative abundances of Lactobacillus, modulated Alpha diversity and beta diversity. These results suggest that CO-S-SME an act as a good antidepressant, exhibiting effects via monoamine neurotransmitters, CORT, inflammation cytokines, and intestinal flora.

Herbal Products and Their Active Constituents Used Alone and in Combination with Antibiotics against Multidrug-Resistant Bacteria

The purpose of this review is to summarize the current knowledge acquired on herbal products and their active constituents with antimicrobial activity used alone and in combination with antibiotics against multidrug-resistant bacteria. The most promising herbal products and active constituents used alone against multidrug-resistant bacteria are Piper betle (methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus, extended-spectrum beta-lactamase, Acinetobacter baumannii, Pseudomonas aeruginosa), Glycyrrhiza glabra (methicillin-resistant S. aureus, vancomycin-resistant Enterococcus, P. aeruginosa), and berberine (methicillin-resistant S. aureus, A. baumannii, P. aeruginosa), respectively. The synergistic effect of the combination of herbal products and their active constituents with antibiotics against multidrug-resistant bacteria are also described. These natural antibacterial agents can be promising sources of inhibitors, which can modulate antibiotic activity against multidrug-resistant bacteria, especially as efflux pump inhibitors. Other possible mechanisms of action of herbal therapy against multidrug-resistant bacteria including modification of the bacterial cell wall and/or membrane, inhibition of the cell division protein filamenting temperature sensitive Z-ring, and inhibition of protein synthesis and gene expression, all of which will also be discussed. Our review suggests that combination herbal therapy and antibiotics can be effectively used to expand the spectrum of their antimicrobial action. Therefore, combination therapy against multidrug-resistant bacteria may enable new choices for the treatment of infectious diseases and represents a potential area for future research.

Investigating the Antibacterial Properties of Prospective Scabicides

Scabies is a dermatological disease found worldwide. Mainly in tropical regions, it is also the cause of significant morbidity and mortality due to its association with potentially severe secondary bacterial infections. Current treatment strategies for scabies do not consider the role of opportunistic bacteria, and here we investigate whether current and emerging scabicides can offer any anti-bacterial protection. Using the broth microdilution method, we examined antimicrobial potential of the current scabicide ivermectin and emerging scabies treatments: abametapir, mānuka oil, and its individual β-triketones. Our results demonstrate that the two novel scabicides abametapir and mānuka oil have antimicrobial properties against common scabies-associated bacteria, specifically Staphylococcus aureus, Streptococcus pyogenes, Streptococcus dysgalactiae subsp. equisimilis and Acinetobacter baumannii. The current scabicide ivermectin offers some antimicrobial activity and is capable of inhibiting the growth aforementioned bacteria. This research is important as it could help to inform future best treatment options of scabies, and scabies-related impetigo.

Cinnamon essential oil and its emulsion as efficient antibiofilm agents to combat Acinetobacter baumannii

Acinetobacter baumannii is an emerging nosocomial pathogen resistant to a wide spectrum of antibiotics, with great potential to form a biofilm, which further aggravates treatment of infections caused by it. Therefore, searching for new potent agents that are efficient against A. baumannii seems to be a necessity. One of them, which has already been proven to possess a wide spectrum of biological activities, including antimicrobial effect, is cinnamon essential oil. Still, further increase of antibacterial efficacy and improvement of bioavailability of cinnamon oil is possible by emulsification process. The aim of this study was comparative analysis of cinnamon essential oil and its emulsion against biofilm forming A. baumannii clinical isolates. Furthermore, the investigation of toxicological aspects of possible applications of essential oil and emulsion was done as well. Gas chromatography–mass spectrometry of essential oil indicated trans-cinnamaldehyde as the most abundant component. The cinnamon emulsion was synthesized from cinnamon essential oil by combining modified low- and high- energy methods. Synthesized emulsion was characterized with Fourier-transform infrared spectroscopy and photon correlation spectroscopy. Both substances exhibited significant antibacterial (minimal inhibitory concentrations in the range 0.125–0.5 mg/ml) and antibiofilm effects (inhibitions of formation and reduction of pre-formed biofilm were 47–81 and 30–62%, respectively). Compared to essential oil, the efficacy of emulsion was even stronger considering the small share of pure oil (20%) in the emulsion. The result of biofilm eradication assay was confirmed by scanning electron microscopy. Even though the cytotoxicity was high especially for the emulsion, genotoxicity was not determined. In conclusion, strong antibacterial/antibiofilm effect against A. baumannii of the cinnamon essential oil and the fact that emulsification even potentiated the activity, seems to be of great significance. Observed cytotoxicity implicated that further analysis is needed in order to clearly determine active principles being responsible for obtained antibacterial/antibiofilm and cytotoxic properties.

Ocimum Species: A Review on Chemical Constituents and Antibacterial Activity

Infection by bacteria is one of the main problems in health. The use of commercial antibiotics is still one of the treatments to overcome these problems. However, high levels of consumption lead to antibiotic resistance. Several types of antibiotics have been reported to experience resistance. One solution that can be given is the use of natural antibacterial products. There have been many studies reporting the potential antibacterial activity of the Ocimum plant. Ocimum is known to be one of the medicinal plants that have been used traditionally by local people. This plant contains components of secondary metabolites such as phenolics, flavonoids, steroids, terpenoids, and alkaloids. Therefore, in this paper, we will discuss five types of Ocimum species, namely O. americanum, O. basilicum, O. gratissimum, O. campechianum, and O. sanctum. The five species are known to contain many chemical constituents and have good antibacterial activity against several pathogenic bacteria.

Synergy based extracts of medicinal plants: Future antimicrobials to combat multidrug resistance

The use of herbal medicines and supplements in the last thirty years has increased enormously. Herbal medication has demonstrated promising and effective potential against various diseases. Herbal and phytoconstituent medications are gaining popularity globally and many people are adopting herbal remedies to deal with different health issues. The indiscriminate use of antibiotics, due to the development of antimicrobial resistance, poses an unprecedented problem for human civilization. Bacterial infections are difficult to cure because of the propensity of microbes to acquire resistance to a wide range of antimicrobial drugs. New compounds are being explored and quantified for possible antibacterial activity with little or no side effects. Researchers are investigating the range of therapeutic plants mentioned in Unani, Ayurveda, and Siddha around the globe. Known and commonly acclaimed global databases such as PubMed, Research Gate, Science Direct, Google Scholar, were searched using different search strings such as Indian medicinal plants, multidrug resistance (MDR), thin layer chromatography (TLC), antimicrobials, and Synergism were used in diverse combinations to reclaim numerous citations associated with this area. Thus, the current review aims to shed a light on the information of medicinal plants as a potential foundation of herbal drugs and elucidate how synergism and TLC bioautography plays a crucial role in finding antimicrobial compounds.

Preparation and Characterization of Ginger Essential Oil Microcapsule Composite Films

New food packaging has shown research significance in the face of increasing demand for high-quality foods and growing attention paid to food safety. In this study, ginger essential oil microcapsule composite films were prepared by combining microcapsules prepared by a complex coacervation method with gelatin films, and the mechanical properties and active functions of the composite films were analyzed. Fourier-transform infrared spectroscopy and differential scanning calorimetry confirmed the successful encapsulation of ginger essential oil. The scanning electron microscopy of the composite films showed the microcapsules and gelatin film matrix were highly compatible. During the entire storage period, the antioxidant capacity of the ginger essential oil microcapsule films weakened more slowly than ginger essential oil microcapsules and could be maintained at a relatively high level for a long time. The microcapsule films had excellent inhibitory effects on Escherichia coli, Staphylococcus aureus, and Bacillus subtilis. Therefore, the direct addition of microcapsules to a film matrix can broaden the application range of microcapsules and increase the duration of the release of active ingredients. Ginger essential oil microcapsule films are potential biodegradable food packaging films with long-lasting activity.

In vitro evaluation of the antibacterial effects of Cinnamomum zeylanicum essential oil against clinical multidrug-resistant Shigella isolates

As there are little data about the antimicrobial effects of the cinnamon essential oils (EO) against multidrug-resistant (MDR) Shigella species, this study aimed to evaluate the antibacterial activities of Cinnamomum zeylanicum EO against the clinical MDR Shigella isolates. Totally 50 MDR Shigella isolates including 17 (34%) S. flexneri, 20 (40%) S. sonnei, and 13 (26%) S. boydii were collected. The isolates were identified by standard phenotypic and molecular methods. The MDR phenotypes were determined as resistant to three antibiotic classes using disc diffusion. The C. zeylanicum EO was analyzed by gas chromatography/mass spectrometry (GC/MS). The minimum inhibitory concentration (MIC) of cinnamon EO was evaluated by microtiter broth dilution. The most Shigella isolates 38% (n = 19) were resistant to six antibiotics. The ampicillin-amikacin-cefotaxime-erythromycin-ciprofloxacin-cotrimoxazole resistotype was the most prevalent pattern detected in five S. sonnei, four S. boydii, and three S. flexneri isolates. The result of GC/MS revealed the cinnamaldehyde (84.8%) as the main ingredient of C. zeylanycum EO. The most susceptible strain to the C. zeylanycum EO was S. boydii (MIC range = 0.15-0.62 μl/ml) followed by S. flexneri (MIC range = 0.07-1.25 μl/ml), and S. sonnei (MIC range = 0.15-1.25 μl/ml). The observed ranges of MIC and MBC values of cinnamon EO against Shigella spp. were 0.07-1.25 μl/ml and 0.31-1.25 μl/ml, respectively. The antibacterial effects of cinnamon EO in this study may increase the hope of finding suitable plant compounds to treat infections caused by MDR Shigella isolates.

Chemical Composition and Antimicrobial Effectiveness of Ocimum gratissimum L. Essential Oil Against Multidrug-Resistant Isolates of Staphylococcus aureus and Escherichia coli

The study investigated the antimicrobial activity of the essential oil extract of Ocimum gratissimum L. (EOOG) against multiresistant microorganisms in planktonic and biofilm form. Hydrodistillation was used to obtain the EOOG, and the analysis of chemical composition was done by gas chromatography coupled with mass spectrometry (GC/MS) and flame ionization detection (GC/FID). EOOG biological activity was verified against isolates of Staphylococcus aureus and Escherichia coli, using four strains for each species. The antibacterial action of EOOG was determined by disk diffusion, microdilution (MIC/MBC), growth curve under sub-MIC exposure, and the combinatorial activity with ciprofloxacin (CIP) and oxacillin (OXA) were determined by checkerboard assay. The EOOG antibiofilm action was performed against the established biofilm and analyzed by crystal violet, colony-forming unit count, and SEM analyses. EOOG yielded 1.66% w/w, with eugenol as the major component (74.83%). The MIC was 1000 µg/mL for the most tested strains. The growth curve showed a lag phase delay for both species, mainly S. aureus, and reduced the growth level of E. coli by half. The combination of EOOG with OXA and CIP led to an additive action for S. aureus. A significant reduction in biofilm biomass and cell viability was verified for S. aureus and E. coli. In conclusion, EOOG has relevant potential as a natural alternative to treat infections caused by multiresistant strains.

Essential Oils as Antimicrobial Agents-Myth or Real Alternative?

Herbs and the essential oils derived from them have been used from the beginning of human history for different purposes. Their beneficial properties have been applied to mask unpleasant odors, attract the attention of other people, add flavor and aroma properties to prepared dishes, perfumes, and cosmetics, etc. Herbs and essential oils (EOs) have also been used in medicine because of their biological properties, such as larvicidal action, analgesic and anti-inflammatory properties, antioxidant, fungicide, and antitumor activities, and many more. Many EOs exhibit antimicrobial properties, which is extremely important in fields of science and industry, such as medicine, agriculture, or cosmetology. Among the 250 EOs which are commercially available, about a dozen possess high antimicrobial potential. According to available papers and patents, EOs seem to be a potential alternative to synthetic compounds, especially because of the resistance that has been increasingly developed by pathogenic microorganisms. In this review we summarize the latest research studies about the most-active EOs that are known and used because of their antimicrobial properties. Finally, it is noteworthy that the antimicrobial activities of EOs are not preeminent for all strains. Further investigations should, thus, focus on targeting EOs and microorganisms.

Recent perspectives on the virulent factors and treatment options for multidrug-resistant Acinetobacter baumannii

Acinetobacter baumannii (AB) is one of the most notorious and opportunistic pathogens, which caused high morbidity and mortality rate and World Health Organization (WHO) declared this bacterium as priority-1 pathogen in 2017. The current antibacterial agents, such as colistins, carbapenems, and tigecyclines have limited applications, which necessitate novel and alternative therapeutic remedies. Thus, the understanding of recent perspectives on the virulent factors and antibiotic resistance mechanism exhibited by the bacteria are extremely important. In addition to many combinatorial therapies of antibacterial, there is several natural compounds demonstrated significant antibacterial potential towards these bacteria. The computational systems biology and high throughput screening approaches provide crucial insights in identifying novel drug targets and lead molecules with therapeutics potential. Hence, this review provides profound insight on the recent aspects of the virulent factors associated with AB, role of biofilm formation in drug resistance and the mechanisms of multidrug resistance. This review further illustrates the status of current therapeutic agents, scope, and applications of natural therapeutics, such as herbal medicines and role of computational biology, immunoinformatics and virtual screening in novel lead developments. Thus, this review provides novel insight on latest developments in drug-resistance mechanism of multidrug-resistant A. baumannii (MDRAB) and discovery of probable therapeutic interventions.