The in vitro antimicrobial effect of azelaic acid

Molecular mechanisms of microbiome modulation by the eukaryotic secondary metabolite azelaic acid

Photosynthetic eukaryotes, such as microalgae and plants, foster fundamentally important relationships with their microbiome based on the reciprocal exchange of chemical currencies. Among these, the dicarboxylate metabolite azelaic acid (Aze) appears to play an important, but heterogeneous, role in modulating these microbiomes, as it is used as a carbon source for some heterotrophs but is toxic to others. However, the ability of Aze to promote or inhibit growth, as well as its uptake and assimilation mechanisms into bacterial cells are mostly unknown. Here, we use transcriptomics, transcriptional factor coexpression networks, uptake experiments, and metabolomics to unravel the uptake, catabolism, and toxicity of Aze on two microalgal-associated bacteria, Phycobacter and Alteromonas, whose growth is promoted or inhibited by Aze, respectively. We identify the first putative Aze transporter in bacteria, a 'C4-TRAP transporter', and show that Aze is assimilated through fatty acid degradation, with further catabolism occurring through the glyoxylate and butanoate metabolism pathways when used as a carbon source. Phycobacter took up Aze at an initial uptake rate of 3.8×10-9 nmol/cell/hr and utilized it as a carbon source in concentrations ranging from 10 μM to 1 mM, suggesting a broad range of acclimation to Aze availability. For growth-impeded bacteria, we infer that Aze inhibits the ribosome and/or protein synthesis and that a suite of efflux pumps is utilized to shuttle Aze outside the cytoplasm. We demonstrate that seawater amended with Aze becomes enriched in bacterial families that can catabolize Aze, which appears to be a different mechanism from that in soil, where modulation by the host plant is required. This study enhances our understanding of carbon cycling in the oceans and how microscale chemical interactions can structure marine microbial populations. In addition, our findings unravel the role of a key chemical currency in the modulation of eukaryote-microbiome interactions across diverse ecosystems.

Extraction and Quantification of Azelaic Acid from Different Wheat Samples (Triticum durum Desf.) and Evaluation of Their Antimicrobial and Antioxidant Activities

Azelaic Acid (AzA) is a 9-carbon atom dicarboxylic acid, with numerous pharmacological uses in dermatology. Its effectiveness in papulopustular rosacea and acne vulgaris, among other dermatological disorders such as keratinization and hyper-pigmentation, is thought to be related to its anti-inflammatory and antimicrobial properties. It is a by-product of Pityrosporum fungal mycelia metabolism but also it is found in different cereals such as barley, wheat, and rye. Diverse topical formulations of AzA exist in commerce, and it is mainly produced via chemical synthesis. In this study we describe the extraction of AzA from whole grains and whole-grain flour (Triticum durum Desf.) through green methods. Seventeen different extracts were prepared and analyzed for their AzA content by HPLC-MS methods and then screened for their antioxidant activity using spectrophotometric assays (ABTS, DPPH, and Folin-Ciocalteu). Minimum-inhibitory-concentration (MIC) assays against several bacterial and fungal pathogens were performed, to validate their antimicrobial activity. The obtained results indicate that whole grain extracts provide a wider spectrum of activity than the flour matrix; in particular, the Naviglio^® extract showed higher AzA content, while the hydroalcoholic ultrasound-assisted extract provided better antimicrobial and antioxidant activity. The data analysis was performed using principal component analysis (PCA), as an unsupervised-pattern-recognition technique, to extract useful analytical and biological information.

Host-guest synergistic enhancement of antibacterial effect by a supramolecular strategy

A supramolecular synergistic antibacterial strategy involving direct complexation of a commercial antibacterial agent, azelaic acid (AzA) by a cationic pillar[5]arene (WP5A) is described. The formation of AzA/WP5A complex could exert synergistic antibacterial effect, leading to promote wound healing efficacy and reduce bacterial burden on S. aureus-infected mice models.

The Genus Alternanthera: Phytochemical and Ethnopharmacological Perspectives

Ethnopharmacological relevance: The genus Alternanthera (Amaranthaceae) comprises 139 species including 14 species used traditionally for the treatment of various ailments such as hypertension, pain, inflammation, diabetes, cancer, microbial and mental disorders.

Aim of the review: To search research gaps through critical assessment of pharmacological activities not performed to validate traditional claims of various species of Alternanthera. This review will aid natural product researchers in identifying Alternanthera species with therapeutic potential for future investigation.

Materials and methods: Scattered raw data on ethnopharmacological, morphological, phytochemical, pharmacological, toxicological, and clinical studies of various species of the genus Alternanthera have been compiled utilizing search engines like SciFinder, Google Scholar, PubMed, Science Direct, and Open J-Gate for 100 years up to April 2021.

Results: Few species of Alternanthera genus have been exhaustively investigated phytochemically, and about 129 chemical constituents related to different classes such as flavonoids, steroids, saponins, alkaloids, triterpenoids, glycosides, and phenolic compounds have been isolated from 9 species. Anticancer, antioxidant, antibacterial, CNS depressive, antidiabetic, analgesic, anti-inflammatory, and immunomodulator effects have been explored in the twelve species of the genus. A toxicity study has been conducted on 3 species and a clinical study on 2 species.

Conclusions: The available literature on pharmacological studies of Alternanthera species reveals that few species have been selected based on ethnobotanical surveys for scientific validation of their traditional claims. But most of these studies have been conducted on uncharacterized and non-standardized crude extracts. A roadmap of research needs to be developed for the isolation of new bioactive compounds from Alternanthera species, which can emerge out as clinically potential medicines.

Gas chromatography–mass spectrometry (GC–MS) analysis of ethyl acetate root bark extract of Strychnos innocua (Delile)

Background

Majority of phytochemicals have been known to bear valuable therapeutic activities such as insecticidal, antibacterial, antifungal, anticonstipative, spasmolytic, antiplasmodial and antioxidant activities. Strychnos innocua is straight-stemmed tree belonging to the family Loganiaceae and can grow up to 18 m tall. The plant is used for various pharmacological purposes. The aim of this study was to determine the chemical composition of the ethyl acetate extract of root bark of S. innocua using GC–MS analysis. The root bark was collected, air-dried and then crushed to powder. Standard extraction method (maceration) was used to obtain the ethyl acetate extract. The GC–MS was carried out on the extract using GC 7890B, MSD 5977A, Agilent Tech.

Results

Thirty-seven compounds were identified among which dibutyl benzene-1,2-dicarboxylate showed the highest peak area (31.03%) and monomethyl pimelate showed the lowest peak area (0.39%). The major compounds identified were cyclooctane (methoxymethoxy), 2,4-dimethylheptanedioic acid dimethyl ester, azelaic acid, 1,2-benzenedicarboxylic acid, bis(2-methylpropyl) ester, dibutyl benzene-1,2-dicarboxylate, butyl 8-methylnonyl benzene-1,2-dicarboxylate, 9,15-octadecadienoic acid, methyl ester, cis-vaccenic acid, linoleic acid ethyl ester and ethyl oleate.

Conclusions

In conclusion, these phytoconstituents might be responsible for the medicinal efficacy of the root bark of S. innocua and can be used as a source therapeutic drug.

[Malassezia spp.: interactions with topically applied lipids-a review : Malassezia and topically applied lipids]

Lipophilic Malassezia yeasts are an important part of the human resident skin flora, especially in seborrheic areas. Besides mutualistic interactions with the host they are also linked to diseases although the specific causes are not yet comprehensively understood. The amount of available lipids on the skin correlates with the Malassezia density and also with the occurrence of certain diseases like tinea versicolor. Here, the naturally produced lipids of the sebaceous glands play a role. Hardly studied thus far is the impact of topically applied lipids. Here, growth promotion as well as inhibition of Malassezia cells as well as the production of new metabolites through ester cleavage are possible. One example is the release of antimicrobial fatty acids from hydroxypropyl caprylate through the action of Malassezia lipases. This "self-kill" principle results in the reduction of the amount of Malassezia cells and can be applied as new therapy option for dandruff treatment. A better understanding of the interaction between topica and Malassezia would increase their skin tolerance and open new therapy options.

Preparation and Evaluation of Azelaic Acid Topical Microemulsion Formulation: In Vitro and In Vivo Study

The aim of this study was to design oil in water (O/W) microemulsion formulations for the topical administration of azelaic acid. The permeability of azelaic acid through rat skin and the anti-inflammatory activities of the formulations were conducted to examine the efficacy of the designed formulations. Skin irritation and stability tests were also performed. The permeability of azelaic acid was significantly increased by using O/W microemulsions as carriers. The edema index of ear swelling percentage was significantly recovered by the 5% drug-loaded formulation and a 20% commercial product, demonstrating that the experimental formulation possessed comparable effect with the commercial product on the improvement of inflammation. The experimental formulation did not cause significant skin irritation compared to the negative control group. Moreover, the drug-loaded formulation also showed thermodynamic stability and chemical stability after storage for 30 days. In conclusion, the O/W microemulsion was a potential drug delivery carrier for azelaic acid topical application.

Antibacterial Activity and Metabolomics Profiling of Torch Ginger (Etlingera elatior Jack) Flower Oil Extracted Using Subcritical Carbon Dioxide (CO2)

The aim of this study was to identify the bioactive compound and evaluate the antibacterial activity of torch ginger flower oil extracted using subcritical carbon dioxide. The antibacterial activity was evaluated in agar diffusion assay, while MIC and MBC were determined using the microdilution broth assay. The essential oil was subjected to metabolomics profiling using GC-MS and 1H-NMR techniques. The results demonstrated strong antibacterial activity towards Salmonella typhimurium, Staphylococcus aureus, and Escherichia coli. The MIC values were 0.0625, 0.25, and 0.25 mg/mL, and the MBC values were 0.25, 0.5, and 1 mg/mL towards S. typhimurium, S. aureus, and E. coli, respectively. A total of 33 compounds were identified using GC-MS including 15 compounds (45%) known for their antimicrobial activity. In addition, sixteen metabolites were identified using NMR analysis and 8 out of the sixteen metabolites (50%) have antibacterial activity. The extracted oil demonstrated broad range for antibacterial activity and has high potential for applications in pharmaceutical and food industries. Practical Applications. The oil extracted from the torch ginger flower was found very stable and has promising applications as antibacterial agent for food and pharmaceutical industries.

Fatty Acids and Antioxidants in Multiple Sclerosis: Therapeutic Role of GEMSP

Multiple sclerosis is a high-frequency neurological disorder in young adults. Although there are some genetic and environmental factors that have been related to the onset of the disease, these are still not completely understood and nowadays multiple sclerosis can neither be prevented, nor its symptom effectively treated due to disease heterogeneity. For this reason, the search of prognostic factors and new therapeutic compounds for MS has long aroused among clinicians and researchers. Among these therapeutic compounds, GEMSP, which consists of a mixture of functional constituents as fatty acids, antioxidants, free radical scavengers and amino acids linked individually to poly-L-Lysine (PL), is emerging as a promising drug for MS treatment. Pre-clinical studies using GEMSP have demonstrated that this drug strongly inhibits brain leukocyte infiltration and completely abolishes experimental autoimmune encephalomyelitis. In addition, in an open clinical trial in humans treated with GEMSP, in 72% of the cases, a positive evolution of the state of the MS patients treated with GMSP was observed. In this review a biochemical characterization of main constituents of GEMSP, which include fatty acids as oleic acid, linoleic acid or azelaic acid and the antioxidants alpha-tocopherol or ascorbic acid, will be provided in order to understand their proved therapeutic effects in MS.

In vitro Antimicrobial Activity of Acne Drugs Against Skin-Associated Bacteria

Acne is a common skin affliction that involves excess sebum production and modified lipid composition, duct blockage, colonization by bacteria, and inflammation. Acne drugs target one or more of these steps, with antibiotics commonly used to treat the microbial infection for moderate to severe cases. Whilst a number of other acne therapies are purported to possess antimicrobial activity, this has been poorly documented in many cases. We conducted a comparative analysis of the activity of common topical acne drugs against the principal etiological agent associated with acne: the aerotolerant anaerobic Gram-positive organism Propionibacterium acnes (recently renamed as Cutibacterium acnes). We also assessed their impact on other bacteria that could also be affected by topical treatments, including both antibiotic-sensitive and antibiotic-resistant strains, using broth microdilution assay conditions. Drugs designated specifically as antibiotics had the greatest potency, but lost activity against resistant strains. The non-antibiotic acne agents did possess widespread antimicrobial activity, including against resistant strains, but at substantially higher concentrations. Hence, the antimicrobial activity of non-antibiotic acne agents may provide protection against a background of increased drug-resistant bacteria.

The spent culture supernatant of Pseudomonas syringae contains azelaic acid

Background

Pseudomonas syringae pv. actinidiae (PSA) is an emerging kiwifruit bacterial pathogen which since 2008 has caused considerable losses. No quorum sensing (QS) signaling molecule has yet been reported from PSA and the aim of this study was to identify possible intercellular signals produced by PSA.

Results

A secreted metabolome analysis resulted in the identification of 83 putative compounds, one of them was the nine carbon saturated dicarboxylic acid called azelaic acid. Azelaic acid, which is a nine-carbon (C9) saturated dicarboxylic acid, has been reported in plants as a mobile signal that primes systemic defenses. In addition, its structure,(which is associated with fatty acid biosynthesis) is similar to other known bacterial QS signals like the Diffusible Signal Facor (DSF). For these reason it could be acting as s signal molecule. Analytical and structural studies by NMR spectroscopy confirmed that in PSA spent supernatants azelaic acid was present. Quantification studies further revealed that 20 μg/L of were present and was also found in the spent supernatants of several other P. syringae pathovars. The RNAseq transcriptome study however did not determine whether azelaic acid could behave as a QS molecule.

Conclusions

This study reports of the possible natural biosynthesis of azelaic acid by bacteria. The production of azelaic acid by P. syringae pathovars can be associated with plant-bacteria signaling.

Electronic supplementary material

The online version of this article (10.1186/s12866-018-1352-z) contains supplementary material, which is available to authorized users.

Shaping of cutaneous function by encounters with commensals

The skin is the largest organ in the human body and provides the first line of defence against environmental attack and pathogen invasion. It harbor multiple commensal microbial communities at different body sites, which play important roles in sensing the environment, protecting against colonization and infection of pathogens, and guiding the host immune system in response to foreign invasions. The skin microbiome is largely variable between individuals and body sites, with several core commensal members commonly shared among individuals at the healthy state. These microbial commensals are essential to skin health and can potentially lead to disease when their abundances and activities change due to alterations in the environment or in the host. While recent advances in sequencing technologies have enabled a large number of studies to characterize the taxonomic composition of the skin microbiome at various body sites and under different physiological conditions, we have limited understanding of the microbiome composition and dynamics at the strain level, which is highly important to many microbe-related diseases. Functional studies of the skin microbial communities and the interactions among community members and with the host are currently scant, warranting future investigations. In this review, we summarize the recent findings on the skin microbiome, highlighting the roles of the major commensals, including bacteria, fungi and bacteriophages, in modulating skin functions in health and disease. Functional studies of the skin microbiota at the metatranscriptomic and proteomic levels are also included to illustrate the interactions between the microbiota and the host skin.

Metal organic frameworks based on bioactive components

This review highlights the latest advances of Metal Organic Frameworks (MOFs) in the promising biomedical domain, from their synthesis to their biorelated activities.

A prodrug approach to enhance azelaic acid percutaneous availability

Azelaic acid is a dicarboxylic acid compound used in treatment of acne vulgaris. However, high concentration (ca 20%) is needed to guarantee the drug availability in the skin. The latter increases the incidence of side effects such as local irritation. The prodrug strategy to enhance azelaic acid diffusion through skin was not reported before. Thus, a lipophilic prodrug of azelaic acid (diethyl azelate [DEA]) was synthesized and investigated to improve percutaneous availability of azelaic acid, with a subsequent full physical, chemical, and biological characterization. Expectedly, DEA exhibited a significant increase in diffusion compared to azelaic acid through silicone membrane. In contrast, the diffusion results through human stratum corneum (SC) displayed weaker permeation for DEA with expected retention in the SC. Therefore, a desorption study of DEA from SC was conducted to examine the reservoir behavior in SC. Results showed an evidence of sustained release behavior of DEA from SC. Consequently, enhancement of keratolytic effect is expected due to azelaic acid produced from enzymatic conversion of DEA released from SC.

Experience of applying azelaic acid in dermatology

The article presents current published data on 30 years of experience in applying of azelaic acid in dermatology. Data on pharmacokinetics, efficacy and safety in the international practice; results of study and therapeutic efficacy of different dosage forms are presented.

Influence of azelaic acid on acne pathogenesis

I In current literature review the physicochemical properties, peculiarities of mode of action and pharmacokinetics of azelaic and influence of azelaic on pathogenetic aspects of acne are characterized.

The Role of Topical Brimonidine Tartrate Gel as a Novel Therapeutic Option for Persistent Facial Erythema Associated with Rosacea

Rosacea is a chronic inflammatory skin condition that commonly presents with persistent facial erythema with or without the coincident presence of flushing, telangiectasias, inflammatory papules or pustules, phymatous changes, or ocular involvement. Patients often present with a constellation of various signs and symptoms of the disease, and an individualized treatment plan should be tailored to a patient's unique clinical presentation. Previously available medications for rosacea have all targeted the inflammatory erythematous papules and pustules frequently associated with the disease, leaving a therapeutic gap for the common manifestation of persistent facial erythema. Brimonidine tartrate 0.33% gel was approved by the US Food and Drug Administration in August 2013 as the first medication available for the topical treatment of persistent facial erythema associated with rosacea. Brimonidine gel is a highly selective α2-adrenergic receptor agonist with potent vasoconstrictive effects, which leads to significant reduction of persistent facial erythema in the majority of patients when applied once daily. Based on large-scale clinical trials and post-marketing reports, brimonidine gel has maintained a good safety profile with a minority of patients experiencing adverse effects from its use, most of which are cutaneous in nature, mild-to-moderate in degree, occur early after initiation of treatment, often resolve spontaneously with continued use, and generally resolve after discontinuation of use. Among the reported adverse effects, two distinct manifestations of worsened erythema have been described. Brimonidine gel can be integrated into a treatment regimen along with concomitant therapies for facial papules and pustules with no increased risk of adverse events with combination therapy. Education about optimal application methods, setting reasonable expectations for treatment, and minimizing inflammation are important factors for the successful use of brimonidine gel as part of a patient's overall rosacea treatment regimen.

Topical acne treatments in Europe and the issue of antimicrobial resistance

Acne vulgaris (acne) is a chronic inflammatory disease of the sebaceous gland, characterized by follicular hyperkeratinization, excessive colonization by Propionibacterium acnes (P. acnes) as well as immune reactions and inflammation. Despite an armamentarium of topical treatments available including benzoyl peroxide, retinoids and azelaic acid, topical antibiotics in monotherapies, especially erythromycin and clindamycin, are still used in Europe to treat acne. This intensive use led to antimicrobial-resistant P. acnes and staphylococci strains becoming one of the main health issues worldwide. This is an update on the current topical acne treatments available in Europe, their mechanism of action, their potential to induce antimicrobial resistance and their clinical efficacy and safety.

Skin diseases associated with Malassezia yeasts: facts and controversies

The implication of the yeast genus Malassezia in skin diseases has been characterized by controversy, since the first description of the fungal nature of pityriasis versicolor in 1846 by Eichstedt. This is underscored by the existence of Malassezia yeasts as commensal but also by their implication in diseases with distinct absence of inflammation despite the heavy fungal load (pityriasis versicolor) or with characteristic inflammation (eg, seborrheic dermatitis, atopic dermatitis, folliculitis, or psoriasis). The description of 14 Malassezia species and subsequent worldwide epidemiologic studies did not reveal pathogenic species but rather disease-associated subtypes within species. Emerging evidence demonstrates that the interaction of Malassezia yeasts with the skin is multifaceted and entails constituents of the fungal wall (melanin, lipid cover), enzymes (lipases, phospholipases), and metabolic products (indoles), as well as the cellular components of the epidermis (keratinocytes, dendritic cells, and melanocytes). Understanding the complexity of their interactions will highlight the controversies on the clinical presentation of Malassezia-associated diseases and unravel the complexity of skin homeostatic mechanisms.

Azelaic acid: Properties and mode of action

Acne is a common skin disorder that can be problematic for adults as well as for adolescents. It has several key pathophysiological features such as follicular hyperkeratosis, elevated Propionibacterium acnes proliferation, and reactive inflammation, all of which should be targeted for an optimal outcome. Azelaic acid (AzA) has profound anti-inflammatory, antioxidative effects, and is bactericidal against a range of Gram-negative and Gram-positive microorganisms as well, including antibiotic-resistant bacterial strains. In addition, AzA's antikeratinizing effects are inhibitory toward comedones. AzA is effective overall in targeting multiple causes of acne and has been proven to be well tolerated in numerous clinical trials.

[Pityriasis versicolor : new aspects of an old disease]

Pityriasis versicolor (PV) is one of the most common infectious skin diseases, as well as the most common dermatosis associated with pigmentation alterations of the skin. PV is prevalent in 1% of the population living in temperate climate zones and more common during the summer. In tropical areas, PV is found in up to 50% of all patients consulting a dermatologist. Of the known Malassezia species, M. globosa is currently felt to play a key role in the pathogenesis of PV, as it is most commonly found in PV lesions. In addition, its round-shaped cells may contribute to the characteristic histology of the disease ("spaghetti and meatballs"). However, the clinical appearance of PV including hyper- and hypopigmentation, fluorescence of the lesions, as well as a lack of inflammation despite high fungal load cannot fully be explained by the presence of M. globosa, which is also found on healthy skin. In M. furfur a tryptophan-dependent metabolic pathway generates a number of indole pigments, which may be associated with the clinical appearance of PV. In the model organism Ustilago maydis it was shown that the formation of the indole compounds occurs spontaneously after initial conversion of tryptophan into indole pyruvate controlled by the key enzyme aminotransferase Tam 1. We review the present knowledge of PV and highlight the potential role of Tam1 in explaining the poorly understood aspects of the disease. Promising therapeutic results using the application of Tam1 inhibitors to treat PV support the enzyme's important role in the disease pathogenesis.

The Malassezia genus in skin and systemic diseases

In the last 15 years, the genus Malassezia has been a topic of intense basic research on taxonomy, physiology, biochemistry, ecology, immunology, and metabolomics. Currently, the genus encompasses 14 species. The 1996 revision of the genus resulted in seven accepted taxa: M. furfur, M. pachydermatis, M. sympodialis, M. globosa, M. obtusa, M. restricta, and M. slooffiae. In the last decade, seven new taxa isolated from healthy and lesional human and animal skin have been accepted: M. dermatis, M. japonica, M. yamatoensis, M. nana, M. caprae, M. equina, and M. cuniculi. However, forthcoming multidisciplinary research is expected to show the etiopathological relationships between these new species and skin diseases. Hitherto, basic and clinical research has established etiological links between Malassezia yeasts, pityriasis versicolor, and sepsis of neonates and immunocompromised individuals. Their role in aggravating seborrheic dermatitis, dandruff, folliculitis, and onychomycosis, though often supported by histopathological evidence and favorable antifungal therapeutic outcomes, remains under investigation. A close association between skin and Malassezia IgE binding allergens in atopic eczema has been shown, while laboratory data support a role in psoriasis exacerbations. Finally, metabolomic research resulted in the proposal of a hypothesis on the contribution of Malassezia-synthesized aryl hydrocarbon receptor (AhR) ligands to basal cell carcinoma through UV radiation-induced carcinogenesis.

Steroid-induced periorificial dermatitis in children--clinical features and response to azelaic acid

Periorificial dermatitis, a common skin disease in young women, has been occasionally reported in children. This study elaborates the clinical features of periorificial dermatitis in children as well as possible pathogenetic factors and the response to 20% azelaic acid cream. A total of 10 children aged 3 to 12 (mean 7.7) years suffering from nongranulomatous periorificial dermatitis for 3 to 7 (mean 4.9) months were evaluated, and dermatologic examination was carried out. Pretreatment was documented. Skin prick tests with a panel of six common inhalative allergens and patch tests with the European Standard Series were performed. An association between atopy and periorificial dermatitis was evaluated, and patients were screened for skin colonization by fungi, bacteria, and Demodex mites. They were treated with 20% azelaic acid cream, which was topically applied twice daily on all affected areas, until complete resolution was achieved. Treatment period was followed by an individual observation period. Periorificial dermatitis had developed in typical distribution and morphology. In all patients, low- to high-potency topical corticosteroids had been used on the face prior to manifestation. Atopy was found in half of the patients. Allergological, bacteriological, and mycological examinations did not reveal pathologic results. Demodex mites could not be demonstrated by skin surface biopsy. Treatment with 20% azelaic acid cream led to complete resolution of skin lesions after 4 to 8 (mean 5.4) weeks in all patients. Transient exacerbation of skin condition with a peak between the 2nd and 6th day of treatment could be observed in three patients. Side effects of 20% azelaic acid cream were registered in six patients and were predominantly present in the first 2 weeks of treatment. Side effects were minimal and became rarer with ongoing treatment. No recurrences were seen within a follow-up period of 2 to 8 (mean 4.4) months. Treatment with 20% azelaic acid cream could provide an effective and safe alternative therapeutic option in children with nongranulomatous periorificial dermatitis.

An in vitro study of antimicrobial activity and efficacy of iodine-generating hydrogel dressings

OBJECTIVE

To determine the antimicrobial activity and efficacy of different formulations of novel bioxygenating hydrogel dressings (which deliver both iodine and oxygen into the wound) against various target organisms by means of an in vitro test system that more effectively mimics the conditions encountered when dressings are in contact with wounds.

METHOD

Three bioxygenating hydrogels were tested: Oxyzyme, which releases low levels of iodine into the wound, and Iodozyme 402 and Iodozyme 401, which release higher levels of iodine, with Iodozyme 402 releasing twice the amount of 401. Cellulose filter disks (n = 32) were inoculated with indicator species and placed equidistant from each other as a matrix onto agar test beds. Cut squares of control or test dressings were placed on top of each disk. Kill curves were constructed from determinations of the numbers of survivors (log cfu per disk) over time by removing disk samples at various time points.

RESULTS

Significant differences (p < 0.05) were observed between the controls and test samples. The order of sensitivity for Oxyzyme was Fusobacterium nucleatum, Bacteroides fragilis, Propionibacterium acnes, Staphylococcus epidermidis, methicillin-resistant Staphylococcus aureus (MRSA), Candida albicans and Pseudomonas aeruginosa. The order of efficacy of the three hydrogel dressings (Iodozyme 402, followed by Iodozyme 401 and then Oxyzyme) was the same regardless of the target species.

CONCLUSION

The novel hydrogel skin surface wound dressings are broad-spectrum in activity, encompassing antibiotic-resistant organisms, anaerobes and yeasts; their antimicrobial function appears to be rapidly effective.

In vitro method to assess the antimicrobial activity and potential efficacy of novel types of wound dressings

AIMS

To develop a simple, reproducible in vitro static diffusion method using cellulose disks and defined species to test antimicrobial efficacy of wound dressings.

METHODS AND RESULTS

Cellulose disks were inoculated by immersion in cell suspensions of target species Staphylococcus epidermidis, Candida albicans and Fusobacterium nucleatum. Test and control wound dressings were cut into equal sized squares (25 x 25 mm) and applied to the surface of 10-mm thick tryptone yeast extract agar on test beds. Following a 2-h equilibration period, inoculated cellulose disks were inserted (one per dressing) at the interface between dressing and agar surface and a small weight applied over each square. At various sampling times, disks were removed and surviving cells enumerated by viable counts. Disk to disk variation for microbial loading was assessed using S. epidermidis for both initial (n = 16) and standard treatment (n = 16) conditions. The coefficient of variation was low (<5%) indicating good reproducibility for cell loading and treatment position on the test bed. Replicate assays (n = 6) using S. epidermidis and oxyzyme gels produced similar kill rates with low scatter (R2 > 0.9) indicating good reproducibility between assays. Significant differences (P < 0.05) in kill rates were observed for different target species, types of dressing and test bed conditions (+/-blood and nutrients).

CONCLUSIONS

The method is reproducible and useful in tracking the death kinetics of test species, enabling the comparison of different types of dressing.

SIGNIFICANCE AND IMPACT OF THE STUDY

The reported method has significant advantages over established test procedures; it can be applied equally across a wide range of target species (including anaerobes and yeasts), a wide range of conditions, and different types of surface dressings, including those relying upon oxygen diffusion.

Evaluation of the antibacterial efficacy of diesters of azelaic acid

A number of diesters of the topical dermatosis treatment azelaic (nonanedioic) acid were prepared and tested for antibacterial effect. Two esters, bis-[(hexanoyloxy)methyl] nonanedioate and especially bis-[(butanoyloxy)methyl] nonanedioate showed promising activity against acne related bacteria in vitro. No activity of azelaic acid was detected in Mueller Hinton II agar at pH 7.3 when using the agar diffusion method, whereas both esters gave zones of growth inhibition. At pH 5.6, activity of azelaic acid was detected. At this pH, the zones of inhibition and MIC values obtained with azelaic acid were smaller than those of bis-[(butanoyloxy)methyl] nonanedioate for all test organisms. A preparation for topical use containing 20% (w/w) bis-[(butanoyloxy)methyl] nonanedioate, and the commercially available Skinoren (20% (w/w) azelaic acid), were compared for antibacterial effect against cutaneous bacteria using contact plate analyses of the skin. Though Skinoren was usually most effective, the differences were not statistically significant. Furthermore, bacteria surviving contact with the topical preparations were invariably more sensitive to the ester than to azelaic acid upon subculturing onto agar (pH 5.6) containing either preparation at 0.2-0.7 mg/ml. This might indicate that other factors, such as the composition of the cream base, mitigate the antibacterial activity of the ester. It is proposed that the pharmacological and microbiological properties of bis-[(butanoyloxy)methyl] nonanedioate are worthy of further study based on an extended screening of acne sufferers.

The thioredoxin system?From science to clinic

The thioredoxin system-formed by thioredoxin reductase and its characteristic substrate thioredoxin-is an important constituent of the intracellular redox milieu. Interactions with many different metabolic pathways such as DNA-synthesis, selenium metabolism, and the antioxidative network as well as significant species differences render this system an attractive target for chemotherapeutic approaches in many fields of medicine-ranging from infectious diseases to cancer therapy. In this review we will present and evaluate the preclinical and clinical results available today. Current trends in drug development are emphasized.

Immunology of diseases associated with Malassezia species

Malassezia species are members of the human cutaneous commensal flora, in addition to causing a wide range of cutaneous and systemic diseases in suitably predisposed individuals. Studies examining cellular and humoral immune responses specific to Malassezia species in patients with Malassezia-associated diseases and healthy controls have generally been unable to define significant differences in their immune response. The use of varied antigenic preparations and strains from different Malassezia classifications may partly be responsible for this, although these problems can now be overcome by using techniques based on recent work defining some important antigens and also a new taxonomy for the genus. The finding that the genus Malassezia is immunomodulatory is important in understanding its ability to cause disease. Stimulation of the reticuloendothelial system and activation of the complement cascade contrasts with its ability to suppress cytokine release and downregulate phagocytic uptake and killing. The lipid-rich layer around the yeast appears to be pivotal in this alteration of phenotype. Defining the nonspecific immune response to Malassezia species and the way in which the organisms modulate it may well be the key to understanding how Malassezia species can exist as both commensals and pathogens.

Frequency and spectrum of Malassezia yeasts in the area of the prepuce and glans penis

OBJECTIVE

To investigate the frequency and spectrum of lipophilic Malassezia yeasts within the area of the glans penis and preputial space in healthy men, most of whom were uncircumcised.

SUBJECTS AND METHODS

As the glans penis and the prepuce are abundant in sebaceous glands, 130 clinically healthy men were examined for the presence of Malassezia spp. Two impression preparations each were made on modified Dixon (mDixon) and Leeming-Notman agar. The media were used with no added cycloheximide to allow the identification of the full spectrum of Candida yeasts. After 10 days of incubation at 32 degrees C Malassezia and Candida yeasts were differentiated by micromorphological and biochemical criteria.

RESULTS

Malassezia spp. were found as part of the microflora of the glans penis in 49% of the men. The two media yielded comparable results for isolation frequency and spectrum: On mDixon agar, 47.6% of the isolates were identified as M. sympodialis, 42.8% as M. globosa, 4.8% as M. pachydermatis and 2.4% as M. furfur. Candida spp. (especially C. albicans) were found in 20.8%. There were no significant differences in the distribution of different Malassezia spp with age.

CONCLUSIONS

Malassezia yeasts may belong to the resident microflora of the male genital region, which is supported by the finding that free sebaceous glands ('Tyson's glands') normally occur at this site. They may also be involved in pathological processes of the glans penis, e.g. balanitis, seborrheic eczema or psoriasis.

Follicular concentrations of azelaic acid after a single topical application

Follicular concentrations of azelaic acid (AzA) were determined in vivo using a rapid, non-invasive method, after a single topical application of 20% (w/w) AzA cream, in order to establish whether the in vitro antimicrobial effects observed in previous studies are relevant in vivo. Preweighed amounts of 20% (w/w) AzA cream were applied over demarcated areas on the forehead and back of nine young adults, and samples were taken over a period of 5 h. AzA was removed from the skin surface by washing with acetone, and follicular casts were collected using cyanacrylate gel. The samples were centrifuged to remove particulate matter, and the supernatants derivatized for analysis by HPLC. Although the results showed wide-ranging variability, the follicular concentration increased as the amount present on the surface declined. The maximum follicular concentrations of AzA attained ranged from 7.5 to 52.5 ng (micrograms of follicular casts)-1 and 0.5 to 23.4 ng (micrograms of follicular casts)-1 in samples taken from the back and forehead, respectively. Assuming an average density of follicular material of 0.9 g ml-1, the mean maximum follicular concentration attained on the back was between 36 and 251 mmol/l, and on the forehead was between 2 and 112 mmol/l, and indicates that the concentration of AzA attained in follicular casts after a single topical application is comparable with the concentration required to inhibit the growth of Propionibacterium acnes and Staphylococcus epidermidis, in vitro.

Inhibitory effect of azelaic acid on neutrophil functions: a possible cause for its efficacy in treating pathogenetically unrelated diseases

It has been shown that acne, hyperpigmentation and lentigo malignant are more or less related pathogenetically to reactive oxygen species (ROS). It has recently been reported that azelaic acid is effective in treating these conditions and that it possesses anti-enzymatic and antimitochondrial activity, including cytochrome-P450 reductase and 5 alpha-reductase in microsomal preparations with nicotinamide adenine dinucleotide phosphate (NADPH). We therefore investigated the effects of azelaic acid on human neutrophil functions, such as chemotaxis, phagocytosis and ROS generation. ROS generation in a cell-free system was also assessed. The results revealed that neutrophil chemotaxis and phagocytosis as well as ROS generated in a xanthine-xanthine-oxidase system were not significantly changed in the presence of azelaic acid. However, azelaic acid markedly decreased O2- and OH. generated by neutrophils. It may be concluded that the reported clinical effectiveness of azelaic acid is partly due to its inhibitory action on neutrophil-generated ROS, leading to a reduction both in oxidative tissue injury at sites of inflammation and in melanin formation.

Azelaic acid. A review of its pharmacological properties and therapeutic efficacy in acne and hyperpigmentary skin disorders

Azelaic acid is a naturally occurring saturated dicarboxylic acid which, on topical application (usually as a 20% cream), has been shown to be effective in the treatment of comedonal acne and inflammatory (papulopustular, nodular and nodulocystic) acne, as well as various cutaneous hyperpigmentary disorders characterised by hyperactive/abnormal melanocyte function, including melasma and, possibly, lentigo maligna. In addition, azelaic acid has an antiproliferative and cytotoxic effect on the human malignant melanocyte, and preliminary findings indicate that it may arrest the progression of cutaneous malignant melanoma. The mechanism of this selective cytotoxic action of azelaic acid is unclear, but may possibly be related to its inhibition of mitochondrial oxidoreductase activity and DNA synthesis. In controlled studies, topical azelaic acid demonstrated comparable anti-acne efficacy to topical tretinoin, benzoyl peroxide, erythromycin and oral tetracycline, while in patients with melasma azelaic acid proved at least as effective as topical hydroquinone. On topical application azelaic acid is well tolerated, with adverse effects apparently limited to a generally mild and transient local cutaneous irritation. Thus, topical azelaic acid, employed either as monotherapy or in combination with other treatments, is likely to prove of value in the management of acne and several hyperpigmentary disorders, most notably melasma.