Antifungal activity of marine-derived actinomycetes against Talaromyces marneffei

Streptomycetes as a promising source of antimicrobial compounds: A GC-MS-based dereplication study

The extensive microbial resistance to existing antimicrobial medicines presents a significant issue in treating diverse microbial infections, whereas actinomycetes remain a viable source of antimicrobial natural products. We planned to employ gas chromatography-mass spectrometry (GC-MS)-based dereplication analysis to investigate the chemical profile of a bioactive actinomycete. Our actinomycete MFS-I31 demonstrated broad antimicrobial potential against the bacterial pathogens Staphylococcus aureus (ATCC 43300), Listeria monocytogenes (ATCC 7644), Escherichia coli (ATCC 25922), and Salmonella enterica (ATCC 14028), as well as the yeast-like fungus Candida albicans (ATCC 60193). The 16S rRNA gene sequencing of the MFS-I31 isolate exhibited a powerful resemblance to Streptomyces species. The characterization of the major antibacterial compounds in its cell-free supernatant (CFS) revealed good stability at different temperatures ranging from 4 °C to 93 °C, whereas the activity was diminished upon precipitation using ammonium sulphate indicating the proteinaceous nature of the major antimicrobial compounds. Notably, the proton nuclear magnetic resonance (1H NMR) revealed peaks in both aromatic and aliphatic areas, demonstrating the variety of the principal secondary metabolites in the crude extract of Streptomyces sp. MFS-I31. Moreover, the GC-MS-based dereplication research of our actinomycete revealed the richness of its chemical profile with different classes of compounds, including volatile molecules with antimicrobial properties. Finally, the contact bioautography demonstrated the good chance of isolating antimicrobial natural products from Streptomyces sp. MFS-I31 if it would be subjected to chemical isolation work. To summarize, soil Streptomycetes remain a valuable source of many antimicrobial natural compounds, particularly when implementing chemical profiling and dereplication studies.

Dermatologic fungal neglected tropical diseases-Part II. Management and morbidity

In this part 2 of a 2-part continuing medical education series, the management, outcomes, and morbidities for fungal skin neglected tropical diseases (NTDs), including eumycetoma, chromoblastomycosis, paracoccidioidomycosis, sporotrichosis, emergomycosis, talaromycosis, and lobomycosis are reviewed. While fungal skin NTDs are associated with poverty in resource-limited settings, they are more often associated with immunosuppression and global migration in the United States. These infections have a high morbidity burden, including disfigurement, physical disability, coinfection, malignant transformation, mental health issues, and financial impact. For most fungal skin NTDs, management is difficult and associated with low cure rates. Dermatologists play a central role in initiating appropriate treatment early in disease course in order to improve patient outcomes.

Exploring marine-derived bacterial compounds targeting the μ-opioid receptor agonists through metabolic profiling to molecular modeling

Given the severe side effects of prolonged morphine use, the search for safer alternatives is a global priority. This study investigates marine bacteria from sediments along the Bejaia coast, Algeria, to identify opioid-like bioactive compounds with potential analgesic properties. A total of 45 bacterial strains were isolated using six different culture media, with 18 strains exhibiting antimicrobial activity. Molecular identification based on 16S rRNA gene sequencing classified these strains into six genera: Streptomyces, Nocardiopsis, Alloalcanivorax, Pseudonocardia, Sinomicrobium, and Lysinibacillus. One strain, S5T2H1, was identified as a new Streptomyces species through a polyphasic approach. LC-HRESIMS analysis of secondary metabolites revealed that strain S56T3J31 produced A58365A, antimycin A, and three potentially novel compounds. However, strain S5T2H1 synthesized cyclo(phenylalanyl-prolyl) and niphimycin Ia, along with three unidentified metabolites, while strain S7T2H1 secreted a single compound identified as berberifuranol. Molecular docking and molecular dynamics simulations demonstrated that A58365A exhibited strong interactions with the μ-opioid receptor (5C1M), showing a stable binding affinity comparable to morphine. These findings highlight marine-derived bacterial compounds as promising candidates for opioid drug development.

Integration of Transcriptomics and Proteomics to Elucidate Inhibitory Effect and Mechanism of Antifungalmycin B from Marine Streptomyces hiroshimensis in Treating Talaromyces marneffei

Talaromyces marneffei (TM) is an opportunistic pathogenic fungus that mainly infects immunocompromised patients. Currently, the global prevalence of talaromycosis caused by TM is increasing, leading to an increased demand for anti-TM drugs. In our previous study, a novel 28-membered macrolide compound, antifungalmycin B (ANB), was isolated from Streptomyces hiroshimensis GXIMD 06359, exhibiting significant antifungal properties. However, its in vivo mechanisms and direct antifungal effects warrant further investigation. In this study, we employed a mouse model in conjunction with transcriptomic and proteomic approaches to explore the antifungal activity of ANB against T. marneffei. In an in vivo mouse model infected with T. marneffei infection, ANB significantly reduced fungal burdens in the liver, spleen, lungs, and kidneys. Additionally, it markedly decreased the levels of reactive oxygen species (ROS) and cytokines, including interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α. Proteomic and transcriptomic studies, complemented by parallel reaction monitoring (PRM) analysis, revealed that ANB effectively disrupted acid biosynthesis and cellular energy metabolism, thereby impairing mitochondrial functions in T. marneffei. These effects were exerted through multiple pathways. These findings highlight the potential of ANB as a versatile inhibitor of polyene macrolide-resistant fungi, offering a promising therapeutic avenue for the treatment of talaromycosis.

GC/MS Fatty Acid Profile of Marine-Derived Actinomycetes from Extreme Environments: Chemotaxonomic Insights and Biotechnological Potential

This study investigated the fatty acids (FA) profile of 54 actinomycete strains isolated from marine sediments collected off the Portugal continental coast, specifically from the Estremadura Spur pockmarks field, by GC/MS. Fatty acid methyl esters (FAMEs) were prepared from the ethyl acetate lipidic extracts of these strains and analyzed by gas chromatography-mass spectrometry (GC/MS), with FA identification performed using the NIST library. The identified FAs varied from C12:0 to C20:0, where 32 distinct FAs were identified, including 7 branched-chain fatty acids (BCFAs), 9 odd-chain fatty acids (OCFAs), 8 monounsaturated fatty acids (MUFAs), 6 saturated fatty acids (SFAs), 1 polyunsaturated fatty acid (PUFA), and 1 cyclic chain fatty acid (CCFA). The average expressed content was BCFA (47.54%), MUFA (28.49%), OCFA (26.93%), and SFA (22.16%), of which i-C16:0, C18:1ω9, and C16:0 were predominant, while PUFA (3.58%) and CCFA (0.41%) were identified as minor components. The identified BCFA were i-C16:0, a-C15:0, i-C15:0, i-C15:1ω6, a-C16:0, a-C14:0, and i-C17:0, which include combined branching and unsaturation and branching and odd. SFAs were present in all species, with C16:0 and C18:0 being the most representative. Rare OCFAs C19:1ω9, C17:1ω7, C15:0, and C17:0 were expressed. PUFA C18:1ω9 was detected; within this class, omega families ω9, ω7, ω6, and ω5 were identified, and no ω3 was detected. The only CCFA was benzene-butanoic acid (benzene-C4:0). These findings highlight the metabolic versatility of actinomycetes, providing valuable insights into microbial chemotaxonomy and offering promising biochemical leads for the development of biofuel, nutraceutical, and antifungal agents. Furthermore, these results underline the diversity and biotechnological potential of FAs in actinomycetes, uncovering their potential to be used as microbial cell factories, and paving the way for innovations in biofuels, pharmaceuticals, and eco-friendly industrial products.

Antifungal activity of bamemacrolactine C against Talaromyces marneffei and its possible mechanisms of action

AIMS

The present study aims to investigate the in vitro antifungal activity and mechanism of action of bamemacrolactine C (BAC), a new 24-membered macrolide compound, against Talaromyces marneffei.

METHODS AND RESULTS

The test drug BAC initially demonstrated antifungal activity through a paper disk diffusion assay, followed by determination of the minimum inhibitory concentration value of 35.29 μg ml-1 using microdilution. The association study revealed that combination therapy exhibited additive effects (0.5 < FICI < 1.0) when combined BAC with either amphotericin B or fluconazole. A time-growth assay confirmed that treatment with 35.29 μg ml-1 of BAC completely inhibited the growth of T. marneffei and exhibited antifungal effects. Micromorphological analysis using scanning electron microscopy and transmission electron microscopy photomicrographs revealed that BAC treatment induced morphological damage in fungal cells compared to the control group. Transmembrane protein assays showed a significant reduction in the levels of Na+/K+-ATPase (P < .05) and Ca2+-ATPase (P < .01) compared to the control group. Intracellular enzyme assays demonstrated that BAC treatment significantly decreased ATP, malate dehydrogenase, and succinate dehydrogenase content (P < .01). The combination of proteomics and parallel reaction monitoring (PRM) verification indicated that BAC exhibits an antifungal mechanism against T. marneffei by downregulating ATP citric acid lyase (ACLY) levels , potentially affecting the tricarboxylic acid (TCA) cycle. Besides, the binding model of BAC and the ACLY also shows a good docking score.

CONCLUSIONS

The findings suggest that BAC exhibits antifungal activity against T. marneffei, elucidating its multifaceted mechanism of action involving disruption of cell membranes' integrity and inhibition of intracellular enzyme activities, in which the modulation of ACLY in the TCA cycle may play an important role.

Development and validation of a colorimetric antifungal susceptibility testing method for the dimorphic fungus Talaromyces marneffei

Antifungal drug resistance is an emerging cause of treatment failure in invasive fungal infections, and antifungal susceptibility testing (AFST) may inform treatment decisions. Currently, there are no established AFST guidelines for Talaromyces marneffei (Tm) or other dimorphic fungi. We developed a colorimetric AFST method using a fluorescent redox indicator alamarBlue, which changes from blue to pink in proportion to cellular metabolic activity. We determined the optimal time for alamarBlue addition to be 24 h post-inoculation and for MIC reading to be 72 h post-inoculation. Our method allows three ways to determine minimum inhibitory concentration (MIC): visual inspection of color change, optical density, and fluorescence intensity. We validated the assay by determining the MICs for seven antifungals against 32 Tm clinical isolates and assessed the essential agreement (EA) and inter-rater reliability between our alamarBlue and the Clinical Laboratory Standard Institute (CLSI) broth microdilution methods. The MIC ranges (from low to high) were: 0.008-0.025 μg/ml for itraconazole, 0.004-0.13 μg/ml for voriconazole, 0.03-0.13 μg/ml for posaconazole, 0.06-0.5 µg/ml for flucytosine, 0.5-1 µg/ml for amphotericin B, 0.5-4 µg/ml for caspofungin, and 0.5-16 µg/ml for fluconazole. The EAs were 100% between all three MIC readouts of the alamarBlue method, and 94%-100% between the alamarBlue and CLSI methods. Our alamarBlue method had substantially higher inter-rater agreement and offers a more reliable method that can be standardized across laboratories in both high- and low-resource settings compared to the established CLSI methodology.

Metabolic Profiling, Antiviral Activity and the Microbiome of Some Mauritian Soft Corals

Soft corals, recognized as sessile marine invertebrates, rely mainly on chemical, rather than physical defense, by secreting intricate secondary metabolites with plausible pharmaceutical implication. Their ecological niche encompasses a diverse community of symbiotic microorganisms which potentially contribute to the biosynthesis of these bioactive metabolites. The emergence of new viruses and heightened viral resistance underscores the urgency to explore novel pharmacological reservoirs. Thus, marine organisms, notably soft corals and their symbionts, have drawn substantial attention. In this study, the chemical composition of four Mauritian soft corals: Sinularia polydactya, Cespitularia simplex, Lobophytum patulum, and Lobophytum crassum was investigated using LC-MS techniques. Concurrently, Illumina 16S metagenomic sequencing was used to identify the associated bacterial communities in the named soft corals. The presence of unique biologically important compounds and vast microbial communities found therein was further followed up to assess their antiviral effects against SARS-CoV-2 and HPV pseudovirus infection. Strikingly, among the studied soft corals, L. patulum displayed an expansive repertoire of unique metabolites alongside a heightened bacterial consort. Moreover, L. patulum extracts exerted some promising antiviral activity against SARS-CoV-2 and HPV pseudovirus infection, and our findings suggest that L. patulum may have the potential to serve as a therapeutic agent in the prevention of infectious diseases, thereby warranting further investigation.

An Overview of Diagnostic and Management Strategies for Talaromycosis, an Underrated Disease

Underrated and neglected, talaromycosis is a life-threatening fungal disease endemic to the tropical and subtropical regions of Asia. In China, it has been reported that talaromycosis mortality doubles from 24 to 50% when the diagnosis is delayed, and reaches 100% when the diagnosis is missed. Thus, the accurate diagnosis of talaromycosis is of utmost importance. Herein, in the first part of this article, we provide an extensive review of the diagnostic tools used thus far by physicians in the management of cases of talaromycosis. The challenges encountered and the perspectives which may aid in the discovery of more accurate and reliable diagnostic approaches are also discussed. In the second part of this review, we discuss the drugs used to prevent and treat T. marneffei infection. Alternative therapeutic options and potential drug resistance reported in the contemporary literature are also discussed. We aim to guide researchers towards the discovery of novel approaches to prevent, diagnose, and treat talaromycosis, and therefore improve the prognosis for those afflicted by this important disease.

An Overlooked and Underrated Endemic Mycosis-Talaromycosis and the Pathogenic Fungus Talaromyces marneffei

Talaromycosis is an invasive mycosis endemic in tropical and subtropical Asia and is caused by the pathogenic fungus Talaromyces marneffei. Approximately 17,300 cases of T. marneffei infection are diagnosed annually, and the reported mortality rate is extremely high (~1/3). Despite the devastating impact of talaromycosis on immunocompromised individuals, particularly HIV-positive persons, and the increase in reported occurrences in HIV-uninfected persons, diagnostic and therapeutic approaches for talaromycosis have received far too little attention worldwide. In 2021, scientists living in countries where talaromycosis is endemic raised a global demand for it to be recognized as a neglected tropical disease. Therefore, T. marneffei and the infectious disease induced by this fungus must be treated with concern. T. marneffei is a thermally dimorphic saprophytic fungus with a complicated mycological growth process that may produce various cell types in its life cycle, including conidia, hyphae, and yeast, all of which are associated with its pathogenicity. However, understanding of the pathogenic mechanism of T. marneffei has been limited until recently. To achieve a holistic view of T. marneffei and talaromycosis, the current knowledge about talaromycosis and research breakthroughs regarding T. marneffei growth biology are discussed in this review, along with the interaction of the fungus with environmental stimuli and the host immune response to fungal infection. Importantly, the future research directions required for understanding this serious infection and its causative pathogenic fungus are also emphasized to identify solutions that will alleviate the suffering of susceptible individuals worldwide.

Juxtaposing Caenorhabditis elegans-Pathogenic Mould Model with Other Models; How Reliable Is This Nematode Model? A Mini Review

The application of Caenorhabditis elegans as a pathogenic model has spanned decades. Its use for pathogenic mould modeling has been attracting some attention lately, though not without some reservations. Several studies have shown C. elegans to be a reliable model for evaluating moulds' virulence factors and patterns as well as for screening the pathogenicity of mutant strains alongside their parental/wild type and revertant/complementary strains. There is a very high degree of reported similarities between the virulence patterns demonstrated in C. elegans and those of other invertebrate and vertebrate models. We have here presented several works in which this nematode model was adopted for virulence evaluation, and other comparative research in which virulence in C. elegans model were juxtaposed with other models. We have further presented possible reasons why there might have been variations of virulence in a few cases, thereby validating C. elegans to be an effective and reliable tool in the study of pathogenic moulds.

Metabolites extracted from microorganisms as potential inhibitors of glycosidases (α-glucosidase and α-amylase): A review

α-Glucosidase and α-amylase are the two main glycosidases that participate in the metabolism of carbohydrates. Inhibitors of these two enzymes are considered an important medical treatment for carbohydrate uptake disorders, such as diabetes and obesity. Microbes are an important source of constituents that have the potential to inhibit glycosidases and can be used as sources of new drugs and dietary supplements. For example, the α-glucosidase inhibitor acarbose, isolated from Actinoplanes sp., has played an important role in adequately controlling type 2 diabetes, but this class of marketed drugs has many drawbacks, such as poor compliance with treatment and expense. This demonstrates the need for new microorganism-derived resources, as well as novel classes of drugs with better compliance, socioeconomic benefits, and safety. This review introduces the literature on microbial sources of α-glucosidase and α-amylase inhibitors, with a focus on endophytes and marine microorganisms, over the most recent 5 years. This paper also reviews the application of glycosidase inhibitors as drugs and dietary supplements. These studies will contribute to the future development of new microorganism-derived glycosidase inhibitors.

Clinical Characteristics, Laboratory Findings, and Prognosis in Patients With Talaromyces marneffei Infection Across Various Immune Statuses

Objective

Talaromyces marneffei (TM) is an opportunistic fungus that is predominantly prevalent among patients who are HIV-positive in South-East Asia. However, few studies focused on the clinical features, laboratory findings, and prognosis across varying immune states.

Methods

A total of 54 patients with TM infection in Xiangya Hospital of Central South University from January 1, 2006 to October 31, 2021 were retrospectively analyzed. Clinical profiles were compared across the different immune statuses by HIV-positive (HIV group, n = 18), HIV negative but with immunocompromised conditions (Non-HIV with IC Group, n = 11), and immunocompetent patients (n = 25).

Results

All the patients were diagnosed by pathogen culture or by metagenomic next-generation sequencing (mNGS). The median age was 50, and patients with HIV were much younger compared to the other two groups. The most common symptom at presentation was fever (79.6%), followed by cough (70.4%), weight loss (61.1%), and expectoration (53.7%). The patients with HIV were more likely to develop into a subtype of disseminated TM affecting multiple organs including lymph node, liver, skin, and spleen, thus, resulting in higher hospital mortality compared to the other two groups. Patients without HIV but with immunocompromised conditions presented similar hospital mortality rates compared to immunocompetent patients, while experiencing longer days of hospitalization to recover from the diseases. Additionally, in this study, the pathogen culture easily confirmed the patients with HIV. However, mNGS presented as a promising tool to confirm TM infection in those suspicious patients without HIV.

Conclusions

In summary, patients with HIV were more likely to develop into disseminated TM, resulting in higher mortality compared to those patients without HIV. Additionally, mNGS presented as an important supplementary tool to confirm TM infection in patients without HIV, particularly in those with immunocompromised diseases.

Caenorhabditis elegans as an Infection Model for Pathogenic Mold and Dimorphic Fungi: Applications and Challenges

The threat burden from pathogenic fungi is universal and increasing with alarming high mortality and morbidity rates from invasive fungal infections. Understanding the virulence factors of these fungi, screening effective antifungal agents and exploring appropriate treatment approaches in in vivo modeling organisms are vital research projects for controlling mycoses. Caenorhabditis elegans has been proven to be a valuable tool in studies of most clinically relevant dimorphic fungi, helping to identify a number of virulence factors and immune-regulators and screen effective antifungal agents without cytotoxic effects. However, little has been achieved and reported with regard to pathogenic filamentous fungi (molds) in the nematode model. In this review, we have summarized the enormous breakthrough of applying a C. elegans infection model for dimorphic fungi studies and the very few reports for filamentous fungi. We have also identified and discussed the challenges in C. elegans-mold modeling applications as well as the possible approaches to conquer these challenges from our practical knowledge in C. elegans-Aspergillus fumigatus model.

Marine Bacterial Secondary Metabolites: A Treasure House for Structurally Unique and Effective Antimicrobial Compounds

The prevalence of antimicrobial resistance reduces the effectiveness of antimicrobial drugs in preventing and treating infectious diseases caused by pathogenic organisms, such as bacteria, fungi, and viruses. Because of the burgeoning growth of microbes with antimicrobial-resistant traits, there is a dire need to identify and develop novel and effective antimicrobial agents to treat infections from antimicrobial-resistant strains. The marine environment is rich in ecological biodiversity and can be regarded as an untapped resource for prospecting novel bioactive compounds. Therefore, exploring the marine environment for antimicrobial agents plays a significant role in drug development and biomedical research. Several earlier scientific investigations have proven that bacterial diversity in the marine environment represents an emerging source of structurally unique and novel antimicrobial agents. There are several reports on marine bacterial secondary metabolites, and many are pharmacologically significant and have enormous promise for developing effective antimicrobial drugs to combat microbial infections in drug-resistant pathogens. In this review, we attempt to summarize published articles from the last twenty-five years (1996–2020) on antimicrobial secondary metabolites from marine bacteria evolved in marine environments, such as marine sediment, water, fauna, and flora.