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Toxins May 2023"Recognizing a surprising fact is the first step towards discovery." This famous quote from Louis Pasteur is particularly appropriate to describe what led us to study... (Review)
Review
"Recognizing a surprising fact is the first step towards discovery." This famous quote from Louis Pasteur is particularly appropriate to describe what led us to study mycolactone, a lipid toxin produced by the human pathogen . is the causative agent of Buruli ulcer, a neglected tropical disease manifesting as chronic, necrotic skin lesions with a "surprising" lack of inflammation and pain. Decades after its first description, mycolactone has become much more than a mycobacterial toxin. This uniquely potent inhibitor of the mammalian translocon (Sec61) helped reveal the central importance of Sec61 activity for immune cell functions, the spread of viral particles and, unexpectedly, the viability of certain cancer cells. We report in this review the main discoveries that marked our research into mycolactone, and the medical perspectives they opened up. The story of mycolactone is not over and the applications of Sec61 inhibition may go well beyond immunomodulation, viral infections, and oncology.
Topics: Animals; Humans; Buruli Ulcer; Mycobacterium ulcerans; Macrolides; Bacterial Toxins; Mammals
PubMed: 37368670
DOI: 10.3390/toxins15060369 -
Antimicrobial Agents and Chemotherapy Apr 2022Buruli ulcer disease is a neglected necrotizing and disabling cutaneous tropical illness caused by Mycobacterium ulcerans. Fluoroquinolone (FQ), used in the treatment of...
Buruli ulcer disease is a neglected necrotizing and disabling cutaneous tropical illness caused by Mycobacterium ulcerans. Fluoroquinolone (FQ), used in the treatment of this disease, has been known to act by inhibiting the enzymatic activities of DNA gyrase. However, the detailed molecular basis of these characteristics and the FQ resistance mechanisms in M. ulcerans remains unknown. This study investigated the detailed molecular mechanism of M. ulcerans DNA gyrase and the contribution of FQ resistance using recombinant proteins from the M. ulcerans subsp. shinshuense and Agy99 strains with reduced sensitivity to FQs. The IC of FQs against Ala91Val and Asp95Gly mutants of M. ulcerans shinshuense and Agy99 GyrA subunits were 3.7- to 42.0-fold higher than those against wild-type (WT) enzyme. Similarly, the quinolone concentrations required to induce 25% of the maximum DNA cleavage (CC) was 10- to 210-fold higher than those for the WT enzyme. Furthermore, the interaction between the amino acid residues of the WT/mutant M. ulcerans DNA gyrase and FQ side chains were assessed by molecular docking studies. This was the first elaborative study demonstrating the contribution of mutations in M. ulcerans DNA GyrA subunit to FQ resistance .
Topics: DNA Gyrase; Drug Resistance, Bacterial; Fluoroquinolones; Microbial Sensitivity Tests; Molecular Docking Simulation; Mutation; Mycobacterium ulcerans; Quinolones
PubMed: 35041504
DOI: 10.1128/AAC.01902-21 -
Microbiology Spectrum Jun 2023Mycobacterium ulcerans, an environmental opportunistic pathogen, causes necrotic cutaneous and subcutaneous lesions, named Buruli ulcers, in tropical countries....
Mycobacterium ulcerans, an environmental opportunistic pathogen, causes necrotic cutaneous and subcutaneous lesions, named Buruli ulcers, in tropical countries. PCR-derived tests used to detect M. ulcerans in environmental and clinical samples do not allow one-shot detection, identification, and typing of M. ulcerans among closely related Mycobacterium marinum complex mycobacteria. We established a 385-member M. marinum/M. ulcerans complex whole-genome sequence database by assembling and annotating 341 M. marinum/M. ulcerans complex genomes and added 44 M. marinum/M. ulcerans complex whole-genome sequences already deposited in the NCBI database. Pangenome, core genome, and single-nucleotide polymorphism (SNP) distance-based comparisons sorted the 385 strains into 10 M. ulcerans taxa and 13 M. marinum taxa, correlating with the geographic origin of strains. Aligning conserved genes identified one (proline-proline-glutamate) gene sequence to be species and intraspecies specific, thereby genotyping the 23 M. marinum/M. ulcerans complex taxa. PCR sequencing of the gene correctly genotyped nine M. marinum/M. ulcerans complex isolates among one M. marinum taxon and three M. ulcerans taxa in the African taxon (T2.4). Further, successful gene PCR sequencing in 15/21 (71.4%) swabs collected from suspected Buruli ulcer lesions in Côte d'Ivoire exhibited positive M. ulcerans 2404 real-time PCR and identified the M. ulcerans T2.4.1 genotype in eight swabs and M. ulcerans T2.4.1/T2.4.2 mixed genotypes in seven swabs. gene sequencing could be used as a proxy for whole-genome sequencing for the one-shot detection, identification, and typing of clinical M. ulcerans strains, offering an unprecedented tool for identifying M. ulcerans mixed infections. We describe a new targeted sequencing approach that characterizes the gene to disclose the simultaneous presence of different variants of a single pathogenic microorganism. This approach has direct implications on the understanding of pathogen diversity and natural history and potential therapeutic implications when dealing with obligate and opportunistic pathogens, such as Mycobacterium ulcerans presented here as a prototype.
Topics: Humans; Buruli Ulcer; Mycobacterium ulcerans; Cote d'Ivoire; Real-Time Polymerase Chain Reaction; Personal Protective Equipment
PubMed: 37222600
DOI: 10.1128/spectrum.00342-23 -
Frontiers in Immunology 2021Mycobacterial diseases are a major public health challenge. Their causative agents include, in order of impact, members of the complex (causing tuberculosis), (causing... (Review)
Review
Mycobacterial diseases are a major public health challenge. Their causative agents include, in order of impact, members of the complex (causing tuberculosis), (causing leprosy), and non-tuberculous mycobacterial pathogens including Macrophages are mycobacterial targets and they play an essential role in the host immune response to mycobacteria. This review aims to provide a comprehensive understanding of the immune-metabolic adaptations of the macrophage to mycobacterial infections. This metabolic rewiring involves changes in glycolysis and oxidative metabolism, as well as in the use of fatty acids and that of metals such as iron, zinc and copper. The macrophage metabolic adaptations result in changes in intracellular metabolites, which can post-translationally modify proteins including histones, with potential for shaping the epigenetic landscape. This review will also cover how critical tuberculosis co-morbidities such as smoking, diabetes and HIV infection shape host metabolic responses and impact disease outcome. Finally, we will explore how the immune-metabolic knowledge gained in the last decades can be harnessed towards the design of novel diagnostic and therapeutic tools, as well as vaccines.
Topics: Adaptation, Physiological; Animals; Host-Pathogen Interactions; Humans; Macrophages; Mycobacterium; Mycobacterium Infections
PubMed: 34630426
DOI: 10.3389/fimmu.2021.747387 -
Scientific Reports Feb 2021Mycobacterium ulcerans secrete a series of non-ribosomal-encoded toxins known as mycolactones that are responsible for causing a disabling ulceration of the skin and...
Mycobacterium ulcerans secrete a series of non-ribosomal-encoded toxins known as mycolactones that are responsible for causing a disabling ulceration of the skin and subcutaneous tissues named Buruli ulcer. The disease is the sole non-contagion among the three most common mycobacterial diseases in humans. Direct contact with contaminated wetlands is a risk factor for Buruli ulcer, responsible for M. ulcerans skin carriage before transcutaneous inoculation with this opportunistic pathogen. In this study, we analysed the bacterial and fungal skin microbiota in individuals exposed to M. ulcerans in Burkina Faso. We showed that M. ulcerans-specific DNA sequences were detected on the unbreached skin of 6/52 (11.5%) asymptomatic farmers living in Sindou versus 0/52 (0%) of those living in the non-endemic region of Tenkodogo. Then, we cultured the skin microbiota of asymptomatic M. ulcerans carriers and negative control individuals, all living in the region of Sindou. A total of 84 different bacterial and fungal species were isolated, 21 from M. ulcerans-negative skin samples, 31 from M. ulcerans-positive samples and 32 from both. More specifically, Actinobacteria, Aspergillus niger and Aspergillus flavus were significantly associated with M. ulcerans skin carriage. We further observed that in vitro, mycolactones induced spore germination of A. flavus, attracting the fungal network. These unprecedented observations suggest that interactions with fungi may modulate the outcome of M. ulcerans skin carriage, opening new venues to the understanding of Buruli ulcer pathology, prophylaxis and treatment of this still neglected tropical infection.
Topics: Aspergillosis; Aspergillus; Burkina Faso; Buruli Ulcer; DNA, Bacterial; Fungi; Humans; Microbiota; Mycobacterium ulcerans; Skin
PubMed: 33580189
DOI: 10.1038/s41598-021-83236-7 -
PLoS Neglected Tropical Diseases Dec 2023Chronic tropical cutaneous ulcers remain a neglected medical condition in West Africa, particularly Buruli ulcer, which is caused by mycolactone cytotoxin-secreting...
BACKGROUND
Chronic tropical cutaneous ulcers remain a neglected medical condition in West Africa, particularly Buruli ulcer, which is caused by mycolactone cytotoxin-secreting Mycobacterium ulcerans (M. ulcerans). Medical management of this highly debilitating and necrotising skin infection may be modified by colonisation and co-infection of the ulcer by opportunistic and pathogenic microorganisms, which considerably delays and increases the cost of treatment.
METHODOLOGY/PRINCIPAL FINDING
We diagnosed chronic tropical cutaneous ulcers in nine patients in Côte d'Ivoire using M. ulcerans-specific PCRs and culturomics. This revealed M. ulcerans in 7/9 ulcer swabs and 5/9 control swabs as well as an additional 122 bacterial species, 32 of which were specific to ulcers, 61 specifics to the controls, and 29 which were shared, adding 40 bacterial species to those previously reported. Whole genome sequencing of four Bordetella trematum (B. trematum) isolates in four Buruli ulcer swabs and no controls indicated cytolethal distending toxins, as confirmed by cytotoxic assay.
CONCLUSIONS/SIGNIFICANCE
In four cases of Buruli ulcer in Côte d'Ivoire, B. trematum was a co-pathogen which was resistant to rifampicin and clarithromycin, unmatching M. ulcerans antibiotic susceptibility profile and counteracting the current treatment of Buruli ulcer in West Africa and Australia. Thus, we report here chronic mixed M. ulcerans-B. trematum chronic tropical ulcer as a specific form of Buruli ulcer in West Africa.
Topics: Humans; Mycobacterium ulcerans; Buruli Ulcer; Ulcer; Cote d'Ivoire; Skin Ulcer; Communicable Diseases
PubMed: 38060465
DOI: 10.1371/journal.pntd.0011413 -
Impact of Temperature and Oxygen Availability on Gene Expression Patterns of Mycobacterium ulcerans.Microbiology Spectrum Mar 2023Buruli ulcer disease is a neglected tropical disease caused by the environmental pathogen Mycobacterium ulcerans. The M. ulcerans major virulence factor is mycolactone,...
Buruli ulcer disease is a neglected tropical disease caused by the environmental pathogen Mycobacterium ulcerans. The M. ulcerans major virulence factor is mycolactone, a lipid cytotoxic compound whose genes are carried on a plasmid. Although an exact reservoir and mode(s) of transmission are unknown, data provide evidence of both. First, Buruli ulcer incidence and M. ulcerans presence have been linked to slow-moving water with low oxygen. M. ulcerans has also been suggested to be sensitive to UV due to termination in , encoding a phytoene dehydrogenase, required for carotenoid production. Further, M. ulcerans has been shown to cause disease following puncture but not when introduced to open abrasion sites, suggesting that puncture is necessary for transmission and pathology. Despite these findings, the function and modulation of mycolactone and other genes in response to dynamic abiotic conditions such as UV, temperature, and oxygen have not been shown. In this study, we investigated modulation of mycolactone and other genes on exposure to changing UV and oxygen microenvironmental conditions. Mycolactone expression was downregulated on exposure to the single stress high temperature and did not change significantly with exposure to UV; however, it was upregulated when exposed to microaerophilic conditions. Mycolactone expression was downregulated under combined stresses of high temperature and low oxygen, but there was upregulation of several stress response genes. Taken together, results suggest that temperature shapes M. ulcerans metabolic response more so than UV exposure or oxygen requirements. These data help to define the environmental niche of M. ulcerans and metabolic responses during initial human infection. Buruli ulcer is a debilitating skin disease caused by the environmental pathogen Mycobacterium ulcerans. M. ulcerans produces a toxic compound, mycolactone, which leads to tissue necrosis and ulceration. Barriers to preventing Buruli ulcer include an incomplete understanding of M. ulcerans reservoirs, how the pathogen is transmitted, and under what circumstances mycolactone and other M. ulcerans genes are expressed and produced in its natural environment and in the host. We conducted a study to investigate M. ulcerans gene expression under several individual or combined abiotic conditions. Our data showed that mycolactone expression was downregulated under combined stresses of high temperature and low oxygen but there was upregulation of several stress response genes. These data are among only a few studies measuring modulation of mycolactone and other M. ulcerans genes that could be involved in pathogen fitness in its natural environment and virulence while within the host.
PubMed: 36912651
DOI: 10.1128/spectrum.04968-22 -
Vaccines Mar 2022The genus mycobacterium includes several species that are known to cause infections in humans. The microorganisms are classified into tuberculous and non-tuberculous... (Review)
Review
The genus mycobacterium includes several species that are known to cause infections in humans. The microorganisms are classified into tuberculous and non-tuberculous based on their morphological characteristics, defined by the dynamic relationship between the host defenses and the infectious agent. Non-tuberculous mycobacteria (NTM) include all the species of mycobacterium other than the ones that cause tuberculosis (TB). The group of NTM contains almost 200 different species and they are found in soil, water, animals-both domestic and wild-milk and food products, and from plumbed water resources such as sewers and showerhead sprays. A systematic review of Medline between 1946 and 2014 showed an 81% decline in TB incidence rates with a simultaneous 94% increase in infections caused by NTM. Prevalence of infections due to NTM has increased relative to infections caused by TB owing to the stringent prevention and control programs in Western countries such as the USA and Canada. While the spread of typical mycobacterial infections such as TB and leprosy involves human contact, NTM seem to spread easily from the environment without the risk of acquiring from a human contact except in the case of in patients with cystic fibrosis, where human transmission as well as transmission through fomites and aerosols has been recorded. NTM are opportunistic in their infectious processes, making immunocompromised individuals such as those with other systemic infections such as HIV, immunodeficiencies, pulmonary disease, or usage of medications such as long-term corticosteroids/TNF-α inhibitors more susceptible. This review provides insight on pathogenesis, treatment, and BCG vaccine efficacy against and some important NTM infections.
PubMed: 35335022
DOI: 10.3390/vaccines10030390 -
Journal of Clinical Microbiology Jun 2023Buruli ulcer (BU) is a neglected tropical disease caused by Mycobacterium ulcerans. Early diagnosis is crucial to prevent morbidity. In November 2012, a field laboratory... (Review)
Review
Buruli ulcer (BU) is a neglected tropical disease caused by Mycobacterium ulcerans. Early diagnosis is crucial to prevent morbidity. In November 2012, a field laboratory fully equipped for the rapid on-site quantitative PCR (qPCR) diagnosis of M. ulcerans was established at the Buruli ulcer treatment center (CDTLUB) center in Pobè Benin, a region where BU is endemic. We describe its first 10 years of activity and its gradual evolution into an expert laboratory for BU diagnosis. From 2012 to 2022, the laboratory analyzed 3,018 samples from patients attending consultations for suspected BU at the CDTLUB in Pobè. Ziehl-Neelsen staining and qPCR targeting the IS2404 sequence were performed. Since 2019, the laboratory has also received and analyzed 570 samples from other centers. The laboratory confirmed the diagnosis of BU by qPCR for 39.7% samples: M. ulcerans DNA was detected in 34.7% of swabs, 47.2% of all fine needle aspiration samples (FNA) and 44.6% of all skin biopsy specimens. Positive Ziehl-Neelsen staining results were obtained for 19.0% samples. Bacterial load, estimated by qPCR, was significantly greater for the Ziehl-Neelsen-positive samples than for Ziehl-Neelsen-negative samples, and detection rates were highest for FNA samples. Overall, 26.3% of the samples received from other centers were positive for BU. Most of these samples were sent by the CDTLUBs of Lalo, Allada, and Zagnanado, Benin. The establishment of the laboratory in the CDTLUB of Pobè has been a huge success. Optimal patient care depends on the close proximity of a molecular biology structure to BU treatment centers. Finally, FNA should be promoted among caregivers. Here, we describe the first 10 years of activity at a field laboratory established at the Buruli ulcer treatment center (CDTLUB) in Pobè, Benin, a country in which Mycobacterium ulcerans is endemic. Between 2012 and 2022, the laboratory analyzed 3,018 samples from patients consulting the CDTLUB of Pobè with a suspected clinical BU. Ziehl-Neelsen staining and qPCR targeting the IS2404 sequence were performed. In total, 39.7% of samples tested positive by qPCR and 19.0% tested positive by Ziehl-Neelsen staining. Detection rates were highest for FNA samples, and the bacterial loads estimated by qPCR were significantly higher for Ziehl-Neelsen-positive samples than for Ziehl-Neelsen-negative samples. Since 2019, the laboratory has also analyzed 570 samples received from outside the CDTLUB of Pobè, 26.3% of which were positive for BU. Most of these samples were sent by the CDTLUBs of Lalo, Allada, and Zagnanado in Benin. The establishment of the laboratory in the CDTLUB of Pobè has been a huge success, with major benefits for both the medical staff and patients. Our findings illustrate that the usefulness and feasibility of having a diagnostic center in rural Africa, where the disease is endemic, is a key part of optimal patient care, and that FNA should be promoted to increase detection rates.
Topics: Humans; Benin; Buruli Ulcer; Coloring Agents; Mobile Health Units; Mycobacterium ulcerans; Polymerase Chain Reaction
PubMed: 37212702
DOI: 10.1128/jcm.00274-23 -
Frontiers in Immunology 2022is the causative agent of Buruli ulcer (BU), the third most common mycobacterial infection. Virulent secretes mycolactone, a polyketide toxin. Most observations of...
is the causative agent of Buruli ulcer (BU), the third most common mycobacterial infection. Virulent secretes mycolactone, a polyketide toxin. Most observations of infection are described as an extracellular milieu in the form of a necrotic ulcer. While some evidence exists of an intracellular life cycle for during infection, the exact role that mycolactone plays in this process is poorly understood. Many previous studies have relied upon the addition of purified mycolactone to cell-culture systems to study its role in pathogenesis and host-response modulation. However, this sterile system drastically simplifies the infection model and assumes that mycolactone is the only relevant virulence factor expressed by . Here we show that the addition of purified mycolactone to macrophages during infection overcomes the bacterial activation of the mechanistic target of rapamycin (mTOR) signaling pathway that plays a substantial role in regulating different cellular processes, including autophagy and apoptosis. To further study the role of mycolactone during infection, we have developed an inducible mycolactone expression system. Utilizing the mycolactone-deficient ::Tn118 strain that contains a transposon insertion in the putative beta-ketoacyl transferase (), we have successfully restored mycolactone production by expressing in a tetracycline-inducible vector system, which overcomes growth defects associated with constitutive complementation. The inducible mycolactone-expressing bacteria resulted in the establishment of infection in a murine footpad model of BU similar to that observed during the infection with wild-type . This mycolactone inducible system will allow for further analysis of the roles and functions of mycolactone during infection.
Topics: Animals; Bacterial Toxins; Buruli Ulcer; Macrolides; Mice; Mycobacterium ulcerans
PubMed: 35401531
DOI: 10.3389/fimmu.2022.750643