Synergistic potential of essential oil combinations against Microsporum, Trichophyton, and Epidermophyton.

Dermatophyte infections globally account for 20 to 25% of fungal infections. Dermatophytes have begun exhibiting antifungal drug resistance, making it challenging to treat this particular infection. Essential oils could be used as alternative solutions as they have been used for a long period to treat different infections. The research has demonstrated the antifungal efficacy of cinnamon, clove, lemongrass, tea tree, thyme, and garlic essential oils, and the impact of their combinations was assayed against Microsporum canis, Trichophyton tonsurans, T. violaceum, T. verrucosum, and Epidermophyton floccosum. Polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) was used to identify the most prevalent M. canis. The accession number of M. canis was obtained as ON007275. All tested essential oils exhibited antidermatophytic action except garlic. A synergistic effect was attained by cinnamon + clove, cinnamon + lemongrass, clove + lemongrass, clove + tea tree, and thyme + tea tree combinations. Concerning antifungal activity, M. canis was the most susceptible dermatophytic species, except in the case of thyme T. violaceum, which was the most susceptible dermatophytic species. The maximum inhibition was recorded in the cases of cinnamon and cinnamon + lemongrass combination against M. canis. The least minimum inhibitory concentrations were attained by cinnamon and clove against M. canis, cinnamon + clove against M. canis and T. violaceum, and cinnamon + lemongrass against M. canis, T. violaceum, T. verrucosum, and E. floccosum. The least minimum fungicidal concentration showed by cinnamon against M. canis, cinnamon + clove against M. canis and T. violaceum, cinnamon + lemongrass against M. canis, T. violaceum, T. verrucosum, and E. floccosum, and clove + lemongrass against M. canis.

Biosurfactant-capped CuO nanoparticles coated cotton/polypropylene fabrics toward antimicrobial textile applications.

The global COVID-19 pandemic has led to an increase in the importance of implementing effective measures to prevent the spread of microorganisms. Consequently, there is a growing demand for antimicrobial materials, specifically antimicrobial textiles and face masks, because of the surge in diseases caused by bacteria and viruses like SARS-CoV-2. Face masks that possess built-in antibacterial properties can rapidly deactivate microorganisms, enabling reuse and reducing the incidence of illnesses. Among the numerous types of inorganic nanomaterials, copper oxide nanoparticles (CuO NPs) have been identified as cost-effective and highly efficient antimicrobial agents for inactivating microbes. Furthermore, biosurfactants have recently been recognized for their potential antimicrobial effects, in addition to inorganic nanoparticles. Therefore, this research's primary focus is synthesizing biosurfactant-mediated CuO NPs, integrating them into natural and synthetic fabrics such as cotton and polypropylene and evaluating the resulting fabrics' antimicrobial activity. Using rhamnolipid (RL) as a biosurfactant and employing a hydrothermal method with a pH range of 9-11, RL-capped CuO NPs are synthesized (RL-CuO NPs). To assess their effectiveness against gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) microorganisms, the RL-CuO NPs are subjected to antibacterial testing. The RL-capped CuO NPs exhibited antimicrobial activity at much lower concentrations than the individual RL, CuO. RL-CuO NPs have shown a minimum inhibitory concentration (MIC) of 1.2 mg ml-1and minimum bactericidal concentration (MBC) of 1.6 mg ml-1forE. coliand a MIC of 0.8 mg ml-1and a MBC of 1.2 mg ml-1forS. aureus, respectively. Furthermore, the developed RL-CuO NPs are incorporated into cotton and polypropylene fabrics using a screen-printing technique. Subsequently, the antimicrobial activity of the coated fabrics is evaluated, revealing that RL-CuO NPs coated fabrics exhibited remarkable antibacterial properties against both gram-positive and gram-negative bacteria.

Comparing minimum inhibitory concentrations of amikacin for pulmonary Mycobacterium avium complex disease: An analysis of culture media differences.

Mycobacterium avium complex (MAC) is considered a paramount microbe, especially in East Asia, including Japan. The commonly used commercial Minimum Inhibitory Concentrations (MIC) assay using Middlebrook 7H9 (7H9) medium deviates from the latest Clinical and Laboratory Standards Institute (CLSI) guidelines. Alternatively, measurement with cation-adjusted Mueller-Hinton broth (CAMHB) that conforms to CLSI standards is not yet widely available. Following the approval and commercialization of amikacin liposome inhalation suspension (ALIS) in 2021, a more precise evaluation of amikacin (AMK) susceptibility in MAC is necessary for treatment decisions. In the present study, 33 sputum samples were extracted from 27 patients, and MICs of AMK were compared between the frequently used 7H9 and the recommended CAMHB of the isolated MAC strains. The history of exposure to aminoglycosides for each sample was also added as clinical information. The findings indicated that there was only an 18% concordance rate in MIC between the two media, with 19 samples (58%) indicating lower MICs in 7H9 relative to CAMHB. The 17 samples had a history of exposure to aminoglycosides for periods ranging from 1.5 to 28 months. Specifically, 10 samples were exposed to amikacin by inhalation and intravenous injection, and the remaining seven samples had a history of ALIS inhalation. Samples with a prior utilization of aminoglycosides were significantly predisposed to developing resistance to ALIS compared to those without such a history (P = 0.046). Physicians are encouraged to scrutinize the findings of susceptibility testing utilizing CLSI-endorsed MIC assay using CAMHB medium to ascertain the optimal therapeutic approach.

Udder health, bacterial isolation and antimicrobial sensitivity of Staphylococcus species from non-dairy goats on smallholder farms in Hong Kong.

This research article describes an investigation into the udder health, bacterial isolation and antimicrobial sensitivity of three staphylococcal species isolated from the milk of non-dairy goats, suckling their kids, on two smallholder farms in the Hong Kong Special Administrative Region. Udder lesions were visually noted in 21 of 34 goats and two goats had palpable abnormalities. Collected milk samples grew a total of 11 bacterial organisms and the most frequently isolated organism was Staphylococcus chromogenes. Selected isolates of S. aureus, caprae and simulans from both farms were tested by antimicrobial sensitivity testing for 23 antimicrobials and all isolates showed antimicrobial resistance to doxycycline and tetracycline. Less common resistance was shown to ampicillin, chloramphenicol, penicillin and rifampicin. This preliminary study confirms the presence of udder lesions and mastitis bacteria in non-dairy goats in Hong Kong, along with the first information on the antimicrobial profile of three common Staphylococcus species bacteria affecting goats.

Cold maceration extraction of wild fruit Terminalia bellirica (Gaertn.) Roxb.: exploring its bioactives for biomedical applications.

Terminalia bellirica (T. bellirica) (Gaertn.) Roxb. is a well-known traditional medicinal plants that show promising treatment because of fewer side effects in humans. In the present study, the total phenol, flavonoid, condensed and hydrolyzable tannins extracted and analyzed from cold macerated (CM) T. bellirica (Gaertn.) Roxb. fruit (TBF) and leaves (TBL) extract with the identification of bioactive compounds using GC-MS/MS technique. The highest amount of bioactive content was found in ethanolic extract than toluene. Current experimental data of TBF extract shows the maximum and significant biological activity like free radical scavenging activity against DPPH and FRAP assays with IC50 values of 51.07 ± 0.52 µg/ml and 63.14 ± 0.59 µg/ml respectively. However, IC50 cytotoxicity values of TBF extract on MCF-7 cells for 24 hrs was found to be 6.34 ± 0.72 µg/ml. Minimum inhibitory concentration (MIC) for infectious pathogens Escherichia coli and Bacillus cereus was >12.5 µg/ml and >100 µg/ml respectively, however, anti-inflammatory activity was demonstrated as an IC50 value of 509.1 ± 1.72 µg/ml. Cold macerated fruit extract revealed threatening inhibitory potential against the α-amylase and α-glucosidase enzymes, with IC50 of 50.98 ± 0.23 µg/ml and 46.70 ± 1.38 µg/ml respectively. Finally, the outcome of this study showed that T. bellirica (Gaertn.) Roxb. fruit extract could be an effective source of bioactives with efficient biomedical properties.

Two Antimicrobial Peptides Derived from Bacillus and Their Properties.

Growth promotion and disease prevention are important strategies in the modern husbandry industry, and for this reason, antibiotics are widely used as animal feed additives. However, the overuse of antibiotics has led to the serious problem of increasing resistance of pathogenic microorganisms, posing a major threat to the environment and human health. "Limiting antibiotics" and "Banning antibiotics" have become the inevitable trends in the development of the livestock feed industry, so the search for alternative antimicrobial agents has become a top priority. Antimicrobial peptides (AMPs) produced by Bacillus spp. have emerged as a promising alternative to antibiotics, due to their broad-spectrum antimicrobial activity against resistant pathogens. In this study, two strains of Bacillus velezensis 9-1 and B. inaquosorum 76-1 with good antibacterial activity were isolated from commercial feed additives, and the antimicrobial peptides produced by them were purified by ammonium sulfate precipitation, anion exchange chromatography, gel chromatography, and RP-HPLC. Finally, two small molecule peptides, named peptide-I and peptide-II, were obtained from strain 9-1 and 76-1, respectively. The molecular weight and sequences of the peptides were analyzed and identified by LC-MS/MS, which were 988.5706 Da and VFLENVLR, and 1286.6255 Da and FSGSGSGTAFTLR, respectively. The results of an antibacterial activity and stability study showed that the two peptides had good antibacterial activity against Staphylococcus aureus, B. cereus, and Salmonella enterica, and the minimum inhibitory concentrations were 64 µg/mL and 16 µg/mL, 32 µg/mL and 64 µg/mL, and 8 µg/mL and 8 µg/mL, respectively. All of them have good heat, acid, and alkali resistance and protease stability, and can be further developed as feed antibiotic substitutes.

Cell free extract-mediated biogenic synthesis of ZnONPs and their application with kanamycin as a bactericidal combination.

Antimicrobial resistance (AMR) is a main public health issue and a challenge for the scientific community all over the globe. Hence, there is a burning need to build new bactericides that resist the AMR. The ZnONPs were produced by cell free extract of mint (Mentha piperita L.) leaves. Antibiotics that are ineffective against resistant bacteria like Escherichia coli and Staphylococcus aureus were treated. The antibiotics were first screened, and then antibacterial activity was checked by disk diffusion, and MIC of Mp-ZnONPs individually and using Kanamycin (KAN) were determined against these pathogens by broth microdilution method. The synergism between Mp-ZnONPs and KAN was confirmed by checkerboard assay. The MIC showed robust antibacterial activity against the tested pathogens. The combination of KAN and Mp-ZnONPs reduces the MIC of KAN as it efficiently inhibits E. coli's growth, and KAN significantly enhances the antibacterial activity of Mp-ZnONPs. Taken together, Mp-ZnONPs have strong antimicrobial activity, and KAN significantly improves it against the tested pathogens, which would offer an effective, novel, and benign therapeutic methodology to regulate the incidence. The combination of Mp-ZnONPs and KAN would lead to the development of novel bactericides, that could be used in the formulation of pharmaceutical products.

In-vitro Antimicrobial Study of Non/irradiated Ylang-ylang Essential Oil Against Multi Drug Resistant Pathogens with Reference to Microscopic Morphological Alterations.

Essential oils have proven to possess great potential in the field of biomedicine due to their ability to effectively eradicate a diverse range of pathogenic microbes. In this study, the antimicrobial activity of ylang-ylang essential oil (YY-EO) was screened against twelve multidrug-resistant pathogens. The YY-EO was effective up to 536 µg/ml, with the highest inhibition zone in case of S. aureus MMCC21 and Escherichia coli MMCC24. The least effect on both Bacillus cereus MMCC11 and Klebsiella pneumonia MMCC16. The major components of the essential oil were identified using GC-MS analysis. Different gamma irradiation doses against the YY-EO were evaluated as a tool of natural decontamination. Moreover, the antimicrobial assay after irradiation proved no significant changes regarding the antimicrobial activity before and after irradiation of EO at the applied dose. The minimum inhibitory concentration (MIC) for the EO against the tested pathogens was detected. The possible morphological changes in some of the bacterial and yeast cells at the recognized MIC and 2MIC were detected using the scanning electron microscope (SEM). Results revealed a notable change in terms of both the microbial cell population and the morphology of the tested bacterial and yeast cells. The cytotoxicity of ylang-ylang EO was evaluated against normal skin tissue culture and showed a potential cytotoxic effect at concentrated doses. These results refer to the importance of YY-EO as a natural antimicrobial agent and the possible application of YY-EO as a surface decontaminant, but they also draw attention to the importance of the EO concentration used in different applications to avoid possible toxic effects. Supplementary Information: The online version contains supplementary material available at 10.1007/s12088-023-01122-4.

In vitro assessment of 17 antimicrobial agents against clinical Mycobacterium avium complex isolates.

BACKGROUND: Recently, Mycobacterium avium complex (MAC) infections have been increasing, especially in immunocompromised and older adults. The rapid increase has triggered a global health concern due to limited therapeutic strategies and adverse effects caused by long-term medication. To provide more evidence for the treatment of MAC, we studied the in vitro inhibitory activities of 17 antimicrobial agents against clinical MAC isolates. RESULTS: A total of 111 clinical MAC isolates were enrolled in the study and they were identified as M. intracellulare, M. avium, M. marseillense, M. colombiense, M. yongonense, and two isolates could not be identified at the species level. MAC strains had relatively low (0-21.6%) resistance to clarithromycin, amikacin, bedaquiline, rifabutin, streptomycin, and clofazimine, and the resistant rates to isoniazid, rifampin, linezolid, doxycycline, and ethionamide were very high (72.1-100%). In addition, M. avium had a significantly higher resistance rate than that of M. intracellulare for ethambutol (92.3% vs 40.7%, P < 0.001), amikacin (15.4% vs 1.2%, P = 0.049), and cycloserine (69.2% vs 25.9%, P = 0.004). CONCLUSIONS: Our results supported the current usage of macrolides, rifabutin, and aminoglycosides in the regimens for MAC infection, and also demonstrated the low resistance rate against new drugs, such as clofazimine, tedizolid, and bedaquiline, suggesting the possible implementation of these drugs in MAC treatment.

Prevalence of Heterotrophic Methylmercury Detoxifying Bacteria across Oceanic Regions.

Microbial reduction of inorganic divalent mercury (Hg2+) and methylmercury (MeHg) demethylation is performed by the mer operon, specifically by merA and merB genes, respectively, but little is known about the mercury tolerance capacity of marine microorganisms and its prevalence in the ocean. Here, combining culture-dependent analyses with metagenomic and metatranscriptomic data, we show that marine bacteria that encode mer genes are widespread and active in the global ocean. We explored the distribution of these genes in 290 marine heterotrophic bacteria (Alteromonas and Marinobacter spp.) isolated from different oceanographic regions and depths, and assessed their tolerance to diverse concentrations of Hg2+ and MeHg. In particular, the Alteromonas sp. ISS312 strain presented the highest tolerance capacity and a degradation efficiency for MeHg of 98.2% in 24 h. Fragment recruitment analyses of Alteromonas sp. genomes (ISS312 strain and its associated reconstructed metagenome assembled genome MAG-0289) against microbial bathypelagic metagenomes confirm their prevalence in the deep ocean. Moreover, we retrieved 54 merA and 6 merB genes variants related to the Alteromonas sp. ISS312 strain from global metagenomes and metatranscriptomes from Tara Oceans. Our findings highlight the biological reductive MeHg degradation as a relevant pathway of the ocean Hg biogeochemical cycle.

Antimicrobial susceptibility of cinnamon and red and common thyme essential oils and their main constituent compounds against Streptococcus suis.

Streptococcus suis is an emerging zoonotic pathogen causing different diseases, in both humans and pigs. Generally, the control of this pathogen is based on antimicrobial therapy, but the development of bacterial resistance has led one to look for new options. In this sense, the essential oils (EOs) constitute a promising alternative. The activity of cinnamon, common thyme and red thyme EOs and their main active compounds (cinnamaldehyde and thymol) against S. suis isolates from pigs (n = 50) and humans (n = 6) was determined by the broth microdilution method. MIC50-90, MBC50-90 and the bactericidal index (BI) (minimal bactericidal concentration (MBC)/minimal inhibitory concentration (MIC)) were calculated. Also, the time-kill curve of each product against the S. suis P1/7 European reference strain was determined. No differences in the MIC or MBC values were observed between all the tested products, which suggest a homogeneous behaviour of S. suis, independently of their origin, organ of isolation or resistance profile. All the products showed a concentration-dependent and time-dependent killing activity and achieved the virtual eradication of S. suis at supra-inhibitory concentrations within the first 5 min of exposure, except cinnamaldehyde that showed only bacteriostatic effect. It suggests that these products could be utilized as antimicrobials in veterinary medicine for the control of this zoonotic pathogen.

Evaluation of the Astragalus exscapus L. subsp. transsilvanicus Roots' Chemical Profile, Phenolic Composition and Biological Activities.

Novel and natural molecules for pharmaceutical applications are a contemporary preoccupation in science which prompts research in underexplored environments. Astragalus exscapus ssp. transsilvanicus (Schur) Nyár. (ASTRA) is a plant species endemic to Transylvania, having a very similar root system with that of A. membranaceus (Fisch.) Bunge, known for its health promoting properties. The present study endeavored to perform basic characterization of the ASTRA roots by proximate analysis, to investigate the fatty acid profile of the lipids extracted from the ASTRA roots, to examine the phenolic composition of the root extracts by liquid chromatography, and to evaluate the biological activities through determination of the antioxidant, antimicrobial and cytotoxic capacities of the extracts. The primary compounds found in the ASTRA roots were carbohydrates and lipids, and the fatty acid composition determined by GC-MS showed linoleic acid as preponderant compound with 31.10%, followed by palmitic, oleic and α-linolenic acids with 17.30%, 15.61% and 14.21%, respectively. The methanol extract of the ASTRA roots presented highest phenolic content, Astragaloside IV being the predominant compound with 425.32 ± 0.06 µg/g DW. The antimicrobial assay showed remarkable antimicrobial potential of the extract at a concentration of 0.356 and 0.703 mg ASTRA root powder (DW)/mL, highlighting its efficacy to inhibit S. aureus and S. epidermidis bacterial strains. Furthermore, the cell proliferation assessment showed the noteworthy proficiency of the treatment in inhibiting the proliferation of B16F10 melanoma cells.

Potential Efficacy of ß-Amyrin Targeting Mycobacterial Universal Stress Protein by In Vitro and In Silico Approach.

The emergence of drug resistance and the limited number of approved antitubercular drugs prompted identification and development of new antitubercular compounds to cure Tuberculosis (TB). In this work, an attempt was made to identify potential natural compounds that target mycobacterial proteins. Three plant extracts (A. aspera, C. gigantea and C. procera) were investigated. The ethyl acetate fraction of the aerial part of A. aspera and the flower ash of C. gigantea were found to be effective against M. tuberculosis H37Rv. Furthermore, the GC-MS analysis of the plant fractions confirmed the presence of active compounds in the extracts. The Mycobacterium target proteins, i.e., available PDB dataset proteins and proteins classified in virulence, detoxification, and adaptation, were investigated. A total of ten target proteins were shortlisted for further study, identified as follows: BpoC, RipA, MazF4, RipD, TB15.3, VapC15, VapC20, VapC21, TB31.7, and MazF9. Molecular docking studies showed that ß-amyrin interacted with most of these proteins and its highest binding affinity was observed with Mycobacterium Rv1636 (TB15.3) protein. The stability of the protein-ligand complex was assessed by molecular dynamic simulation, which confirmed that ß-amyrin most firmly interacted with Rv1636 protein. Rv1636 is a universal stress protein, which regulates Mycobacterium growth in different stress conditions and, thus, targeting Rv1636 makes M. tuberculosis vulnerable to host-derived stress conditions.

Association between high vancomycin minimum inhibitory concentration and clinical outcomes in patients with methicillin-resistant Staphylococcus aureus bacteraemia - A retrospective cohort study.

The purpose of this study is to determine the role of high (≥ 1.5 mg/L) vancomycin minimum inhibitory concentration (VMIC) in predicting clinical outcomes in patients with methicillin-resistant Staphylococcus aureus bacteraemia (MRSAB). A retrospective study was conducted at Mayo Clinic, Minnesota. Patients ≥ 18 years with a 3-month follow-up were included. Outcomes were defined as 30-day all-cause in-hospital mortality, median duration of bacteraemia, metastatic infectious complications, and relapse of MRSAB. A total of 475 patients with MRSAB were identified, and 93 (19.6%) of them had high VMIC isolates. Sixty-four percent of patients were male with a mean age of 69.0 years. Active solid organ malignancy and skin and soft tissue infection as source of MRSAB were associated with high VMIC, while septic arthritis as a complication was significantly associated with low VMIC on multivariate analysis. Eighty-one (17.1%) patients died within 30 days of hospitalization, with no significant difference in mortality rates between the two groups. In-hospital mortality, median duration of bacteraemia, and metastatic infectious complications were not significantly associated with high VMIC MRSAB.

Association between high vancomycin minimum inhibitory concentration and clinical outcomes in patients with methicillin-resistant Staphylococcus aureus bacteremia: a meta-analysis.

PURPOSE: To assess the relationship between high vancomycin minimum inhibitory concentrations (MIC), in patients with methicillin-resistant Staphylococcus aureus bacteremia (MRSAB), and both mortality and complicated bacteremia. METHODS: Embase, Medline, EBM, Scopus and Web of Science were searched for studies published from January 1st 2014 to February 29th 2020. "High" vancomycin MIC cut off was defined as ≥ 1.5 mg/L. Three referees independently reviewed studies that compared outcomes in patients with MRSAB stratified by vancomycin MIC. Subgroup analyses were performed for rates of mortality and complicated bacteremia. RESULTS: A total of 13 studies with 2089 patients were included. Overall, mortality was 27.7% and 23.3% in the high and low vancomycin MIC group, respectively. No significant difference was found between vancomycin MIC groups for overall mortality, in-hospital mortality, late mortality, persistent bacteremia, severe sepsis or septic shock, acute renal failure, septic emboli or endocarditis, and osteomyelitis or septic arthritis. Early mortality was significantly associated with low vancomycin MIC. Mortality in studies using broth microdilution method (BMD) and need for mechanical ventilation were significantly associated with high vancomycin MIC. CONCLUSION: Overall mortality and complicated bacteremia were not significantly associated with high vancomycin MICs in a patient with MRSAB. Randomized controlled trials to assess the utility of vancomycin MIC values in predicting mortality and other adverse clinical outcomes are warranted.

A review on antimicrobial botanicals, phytochemicals and natural resistance modifying agents from Apocynaceae family: Possible therapeutic approaches against multidrug resistance in pathogenic microorganisms.

Accelerated emergence of drug- resistant pathogenic microbes, their unbeatable virulence and a gradual loss of efficacy of currently used antimicrobial agents over the last decade, have expanded the scope of herbal medicine to combat this emerging challenge to have a wide spectrum of activity to develop effective medicines with lesser untoward side effects. Plant-based natural products should be of utmost interest to today's pharmaceutical industries since they are a primary source of new chemical entities directed at new drug targets. Apocynaceae or 'Dogbane' family has attained a global reputation as a source of some life-saving plant-derived products and novel compounds. Members of this family have also been extensively investigated against several nosocomial pathogenic microbes through in vitro and in vivo experimental settings. Several plant-derived components obtained from members of this family have also exhibited remarkable microbial growth inhibitory properties. Popular and widely accepted international databases such as PubMed, Science Direct, ResearchGate, Scopus, Google Scholar, JSTOR and more were searched using the various search strings such as Apocynaceae, antimicrobials, multidrug resistance, resistance modifying agents and pathogenic microorganisms were used in various combinations to retrieve several citations related to the topic. The current review encompasses recent developments in experimental studies and phytochemical analyses which correlates with antimicrobial efficacy of selected Apocynaceous plants along with synergistic mechanism and structural details. The present review recognizes and leverages the importance of Apocynaceae plants, which could be of significant interest in the development of more effective and less toxic antimicrobial drugs which may surmount multidrug resistance. Three different paradigm models harnessing clinical antimicrobial resistance (AMR) including the plant family Apocynaceae, Gram-positive and Gram-negative bacterial species have been broadly discussed in this review. In a nutshell, the present review represents a comprehensive account on the antimicrobials and resistance modifying agents obtained from the members of the plant family Apocynaceae and derived phytochemicals. It also gives an insight into the underlying mode of action of these phytochemicals against an array of pathogenic bacteria, their mechanism of antibiosis, plant parts from which the phytochemicals were isolated or the extracts was prepared with a critical discussion on the botanically-derived antibiotics as a template for antimicrobial drug development.

Antibacterial Activity and Amphidinol Profiling of the Marine Dinoflagellate Amphidinium carterae (Subclade III).

Microalgae have received growing interest for their capacity to produce bioactive metabolites. This study aimed at characterising the antimicrobial potential of the marine dinoflagellate Amphidinium carterae strain LACW11, isolated from the west of Ireland. Amphidinolides have been identified as cytotoxic polyoxygenated polyketides produced by several Amphidinium species. Phylogenetic inference assigned our strain to Amphidinium carterae subclade III, along with isolates interspersed in different geographic regions. A two-stage extraction and fractionation process of the biomass was carried out. Extracts obtained after stage-1 were tested for bioactivity against bacterial ATCC strains of Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa. The stage-2 solid phase extraction provided 16 fractions, which were tested against S. aureus and E. faecalis. Fractions I, J and K yielded minimum inhibitory concentrations between 16 µg/mL and 256 µg/mL for both Gram-positive. A targeted metabolomic approach using UHPLC-HRMS/MS analysis applied on fractions G to J evidenced the presence of amphidinol type compounds AM-A, AM-B, AM-22 and a new derivative dehydroAM-A, with characteristic masses of m/z 1361, 1463, 1667 and 1343, respectively. Combining the results of the biological assays with the targeted metabolomic approach, we could conclude that AM-A and the new derivative dehydroAM-A are responsible for the detected antimicrobial bioactivity.

In vitro assessment of the effect of probiotic lactobacillus reuteri on peri-implantitis microflora.

BACKGROUND: Probiotics affect both the development and stability of microbiota by altering the colonization of pathogens and thus helps in stimulating the immune system of the individual. The aim of the present study is to assess the effect of probiotics on peri-implantitis microflora, by determining the minimum inhibitory concentration (MIC) of Lactobacillus reuteri, that can be effectively administered as an antimicrobial agent on specific peri-implantitis pathogens. Hence, this study will be helpful in finding the MIC of L. Reuteri that can be effectively administered as an antimicrobial agent on specific peri-implantitis pathogens. METHODS: This experimental research was conducted on patients visiting the periodontology department in M. A. Rangoonwala college of dental sciences and research centre. Sub-gingival plaque samples were collected from peri-implantitis patients to identify various peri-implantitis microorganisms. The identified microorganisms were compared to each other and Chi-Square test was used to calculate statistical significance. The isolated microorganisms were subjected to the effect of probiotic Lactobacillus reuteri in-vitro. Minimum inhibitory concentration (MIC) was assessed using serial dilution method. RESULTS: The research results showed the presence of Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Prevotella intermedia, Streptococcus salivaris and Staphylococcus aureus in the subgingival samples from peri-implantitis patients. Statistically, significantly higher proportion of samples had Porphyromonas gingivalis. When subjected to the effect of L. reuteri, all the microorganisms were affected by L.reuteri except Aggregatibacter actinomycetemcomitans. CONCLUSION: This study provides the various MIC value for each isolated pathogen against L.reuteri. The authors recommend to avoid using standard guidelines for probiotic dose in the treatment of peri-implant infections as the antimicrobial profile is different for each periodontal pathogen.

Plant-based oral care product exhibits antibacterial effects on different stages of oral multispecies biofilm development in vitro.

BACKGROUND: Excessive biofilm formation on surfaces in the oral cavity is amongst the main reasons for severe infection development like periodontitis and peri-implantitis. Mechanical biofilm removal as well as the use of adjuvant antiseptics supports the prevention of pathogenic biofilm formation. Recently, the antibacterial effect of the oral care product REPHA-OS®, based on medicinal plant extracts and essential oils, has been demonstrated on oral pathogens grown on agar plates. In the present study, the effectiveness of the product on medical relevant oral biofilm development should be demonstrated for the first time. METHODS: An established in vitro oral multispecies biofilm, composed of Streptococcus oralis, Actinomyces naeslundii, Veillonella dispar and Porphyromonas gingivalis, was used to analyze the antibacterial effect of different REPHA-OS® concentrations on planktonic bacteria, biofilm formation and mature biofilms. It was quantified using metabolic activity assays and live/dead fluorescence staining combined with three-dimensional confocal laser-scanning microscopy. Additionally, effects on species distribution inside the biofilm were assessed by means of quantitative real-time PCR. RESULTS: REPHA-OS® showed statistically significant antimicrobial effects on all stages of biofilm development: a minimal inhibitory concentration of 5% could be detected for both, for planktonic bacteria and for biofilm formation. Interestingly, only a slightly higher concentration of 10% was necessary to completely kill all bacteria in mature biofilms also. In contrast, an influence on the biofilm matrix or the species distribution could not be observed. The effect could be attributed to the herbal ingredients, not to the contained ethanol. CONCLUSION: The strong antibacterial effect of REPHA-OS® on different stages of oral biofilm development strengthens its application as an alternative adjuvant in oral care therapies.

Lipophilic Arginine Esters: The Gateway to Preservatives without Side Effects.

This study hypothesized that long carbon chain cationic arginine (Arg) esters can be considered as toxicologically harmless preservatives. Arg-esters with C18 and C24 carbon chains, namely, arginine-oleate (Arg-OL) and arginine-decyltetradecanoate (Arg-DT), were synthesized. Structures were confirmed by FT-IR, 1H NMR, and mass spectroscopy. Both Arg-esters were tested regarding hydrophobicity in terms of log Poctanol/water, critical micelle concentration (CMC), biodegradability, cytotoxicity, hemolysis, and antimicrobial activity against Escherichiacoli (E. coli), Staphylococcusaureus (S. aureus), Bacillussubtilis (B. subtilis), and Enterococcusfaecalis (E. faecalis). Log Poctanol/water of arginine was raised from -1.9 to 0.3 and 0.6 due to the attachment of C18 and C24 carbon chains, respectively. The critical micelle concentration of Arg-OL and Arg-DT was 0.52 and 0.013 mM, respectively. Both Arg-esters were biodegradable by porcine pancreatic lipase. In comparison to the well-established antimicrobials, benzalkonium chloride (BAC) and cetrimide, Arg-esters showed significantly less cytotoxic and hemolytic activity. Both esters exhibited pronounced antimicrobial properties against Gram-positive and Gram-negative bacteria comparable to that of BAC and cetrimide. The minimum inhibitory concentration (MIC) of Arg-esters was <50 µg mL-1 against all tested microbes. Overall, results showed a high potential of Arg-esters with long carbon chains as toxicologically harmless novel preservatives.