Mycobacterium marinum infection in fish and man: epidemiology, pathophysiology and management; a review

Orchestrated immune responses to Mycobacterium marinum natural infection in tongue sole (Cynoglossus semilaevis)

Mycobacterium marinum is a major pathogen in aquaculture, posing a substantial threat to the health and sustainability of tongue sole (Cynoglossus semilaevis) farming. This study investigated the genetic basis of immune response in tongue sole by comparing transcriptome profiles of liver and spleen tissues from symptomatic (susceptible) and healthy (resistant) individuals during a natural M. marinum outbreak. Transcriptomic analyses identified differentially expressed genes and enriched pathways related to immune responses. Key genes, including atp6ap1, gpi, and idh3a, were found to be crucial in immune response to M. marinum infection, involved in immune processes such as signal transduction, antigen processing, and metabolic pathways. Protein-protein interaction networks highlighted central hub genes such as nedd8, jun and junb, which play pivotal roles in immune regulation. These findings provide insights into the orchestrated immune responses to mycobacteriosis, which can inform selective breeding strategies for disease-resistant tongue sole strains. This is the first comprehensive transcriptome analysis of M. marinum natural infection in tongue sole, offering valuable data for future research and disease management in aquaculture.

Seventeen cases of Mycobacterium marinum infection in Italy: A multicenter retrospective study

Mycobacterium marinum infection is rare, misrecognized and underdiagnosed but can cause severe clinical pictures, especially if the diagnosis is late and the patient is immunocompromised. Treatment includes long-term antibiotic therapy combined with surgical therapy when necessary. We performed a multicenter retrospective study with data from five Italian hospitals describing the epidemiological, clinical, bacteriological characteristics, and treatment outcome of subjects diagnosed with M. marinum infection. During the study period 17 subjects were enrolled. The median time from symptoms onset to diagnosis was 124 days. Thirteen out of 17 were bacteriologically confirmed cases. In all cases, expect one, at least two antibiotics were used with a median of 6 months of treatment, leading to clinical resolution. Too often, the diagnosis of M. marinum infection is delayed and it remains largely presumptive. Prospective studies and randomized controlled trials are necessary to better understand the most appropriate therapeutic regimen and duration.

Mycobacterium marinum infection successfully treated with oral administration of minocycline and thermotherapy

We report a case of a woman presenting with an erythematous finger nodule, with a history of exposure to tropical fish. The erythematous nodules subsequently spread proximally from the finger. Initial treatment with oral amoxicillin-clavulanate was unsuccessful, and she developed a drug eruption. Treatment with oral minocycline and thermotherapy was initiated, as we suspected infection with Mycobacterium marinum (M. marinum) from her history and clinical features. A culture from a skin biopsy from the finger grew M. marinum, confirming the diagnosis. There is no established treatment regimen for skin infections caused by M. marinum. In this case, it took time for cultures to confirm the diagnosis of non-tuberculous mycobacterial infection. While it would be ideal to await culture results, we felt it was better for the patient to initiate treatment, and in M. marinum infections, minocycline is considered particularly effective. However, it was envisaged that this would result in a prolonged treatment course, leading to potential resistance. Thermotherapy was added in an attempt to shorten the treatment period. This regime was successful, and the patient has remained free of recurrence since. The early initiation of treatment for cutaneous non-tuberculous mycobacterial infection requires aggressive suspicion. Also, testing, including adequate sampling and culturing, is essential for an accurate diagnosis. Slow-growing mycobacteria may take several months to be definitively diagnosed, as they grow only under certain conditions. Therefore, thorough clinical history-taking and information sharing with the microbiology team are essential. Our case illustrates this, and we believe this has important educational value.

Cutaneous infection due to Mycobacterium marinum: A series of four cases from Kerala, India

Mycobacterium marinum is a non-tuberculous mycobacterium which can be found in naturally occurring, non-chlorinated water sources and is a known pathogen that affects fish. In humans, M. marinum typically results in cutaneous lesions, it can occasionally lead to more invasive disorders. We discuss four cases of M. marinum-related cutaneous infections examined in a tertiary care facility. We want to draw attention to the challenges of accurately diagnosing this infection, stress the significance of having a high level of clinical suspicion in order to identify it, and discuss the available treatment choices.

Current Challenges of Vaccination in Fish Health Management

Vaccination is an essential method of immunological preventive care required for the health management of all animals, including fish. More particularly, immunization is necessary for in-land aquaculture to manage diseases in fish broodstocks and healthy seed production. According to the latest statistics in 2020, 90.3 million tons of capture fishery production was achieved from the aquaculture sector. Out of the above, 78.8 million tons were from marine water aquaculture sectors, and 11.5 million tons were from inland water aquaculture sectors. About a 4% decline in fish production was achieved in 2020 in comparison to 2018 from inland aquaculture sectors. On the other hand, the digestive protein content, healthy fats, and nutritional values of fish products are comparatively more affordable than in other meat sources. In 2014, about 10% of aquatic cultured animals were lost (costing global annual losses > USD 10 billion) due to infectious diseases. Therefore, vaccination in fish, especially in broodstocks, is one of the essential approaches to stop such losses in the aquaculture sector. Fish vaccines consist of whole-killed pathogens, protein subunits, recombinant proteins, DNA, or live-attenuated vaccines. Challenges persist in the adaption of vaccination in the aquaculture sector, the route of administration, the use of effective adjuvants, and, most importantly, the lack of effective results. The use of autogenous vaccines; vaccination via intramuscular, intraperitoneal, or oral routes; and, most importantly, adding vaccines in feed using top dressing methods or as a constituent in fish feed are now emerging. These methods will lower the risk of using antibiotics in cultured water by reducing environmental contamination.

Mycobacterial biofilms: Understanding the genetic factors playing significant role in pathogenesis, resistance and diagnosis

Even though the genus Mycobacterium is a diverse group consisting of a majority of environmental bacteria known as non-tuberculous mycobacteria (NTM), it also contains some of the deadliest pathogens (Mycobacterium tuberculosis) in history associated with chronic disease called tuberculosis (TB). Formation of biofilm is one of the unique strategies employed by mycobacteria to enhance their ability to survive in hostile conditions. Biofilm formation by Mycobacterium species is an emerging area of research with significant implications for understanding its pathogenesis and treatment of related infections, specifically TB. This review provides an overview of the biofilm-forming abilities of different species of Mycobacterium and the genetic factors influencing biofilm formation with a detailed focus on M. tuberculosis. Biofilm-mediated resistance is a significant challenge as it can limit antibiotic penetration and promote the survival of dormant mycobacterial cells. Key genetic factors promoting biofilm formation have been explored such as the mmpL genes involved in lipid transport and cell wall integrity as well as the groEL gene essential for mature biofilm formation. Additionally, biofilm-mediated antibiotic resistance and pathogenesis highlighting the specific niches, sites of infection along with the possible mechanisms of biofilm dissemination have been discussed. Furthermore, drug targets within mycobacterial biofilm and their role as potential biomarkers in the development of rapid diagnostic tools have been highlighted. The review summarises the current understanding of the complex nature of Mycobacterium biofilm and its clinical implications, paving the way for advancements in the field of disease diagnosis, management and treatment against its multi-drug resistant species.

Mycobacterium marinum hand infection: a case report and literature review

Mycobacterium marinum, a photochromogenic, slow-growing mycobacterium, thrives in both marine and freshwater environments. Optimal growth occurs between 25°C and 35°C, with survival becoming challenging above 37°C. Typically, M. marinum enters the body via skin abrasions, often leading to infections of the upper extremities. Diagnosis of M. marinum infection is frequently challenging and delayed due to the difficult pathogen identification. At present, a standardized treatment protocol has yet to be established. Presented herein is a case study detailing an infection of the right hand's middle finger caused by M. marinum. Notably, his occupation as a chef, handling fish and seafood post-injury, was a significant factor. Histological examination of the skin biopsy and positive acid-fast staining were consistent with a diagnosis of mycobacterial infection. Pathological examination confirmed a skin infection with infectious granuloma, and tissue section acid-fast staining revealed acid-fast bacill. Cultures on Columbia blood agar yielded rough, flattened, yellow-fleshy colonies after 10 days, which was identified as M. marinum through 16S rRNA sequencing. The patient responded well to a 3-month regimen of oral moxifloxacin (0.4 qd) and linezolid (0.6 qd), resulting in rash resolution and pain relief, with no recurrence observed for 1-year follow-up. This report presents the first documented acid-fast staining images of M. marinum tissue sections and colony morphology photographs, offering an in-depth view of M. marinum's morphological characteristics. It aims to enhance awareness of M. marinum infections, underscore the necessity for clinicians to delve into patient histories, and provide a review of the clinical manifestations, diagnostic techniques, therapeutic approaches, and pathogenic mechanisms associated with M. marinum.

Mycobacterium marinum cutanous infection misdiagnosed as sporotrichosis in a patient with systemic lupus erythematosus: A case report

Mycobacterium marinum(M. marinum ), a slow-growing bacterium in freshwater and seawater, can cause cutanous and extracutaneous infections. A fisher-woman with systemic lupus erythematosus (SLE) presented with chronic polymorphic rashes in a lymphangitic pattern was initially misdiagnosed as sporotrichosis. The final diagnosis of M. marinum and Candida dubliniensis co-infection was confirmed based on the skin histopathology, pustule culture, MetaCAP sequencing and effective antibiotic combination treatments.

A Rapid PCR-Based Diagnostic Method for Skin Infection with Mycobacterium marinum

Objective

The increasing incidence of chronic skin infections caused by Mycobacterium marinum, coupled with the time-consuming and low detection rates nature of traditional culture and histological-based diagnostic methods, underscores the need for an expedited approach. The study aims to develop a rapid and efficient method for detecting M. marinum with PCR technology.

Methods

We designed four pairs of primers based on DNA sequences from GeneBank and prior studies, we utilized both PCR and Real-time PCR to identify M. marinum. Specificity and sensitivity assessments were conducted in vitro by DNAs extracted from M. marinum and other bacterial or fungal cultures. Further validation was performed through the implementation of a mouse skin infection model to optimize and confirm the efficacy of the detection method in both fresh and paraffin-embedded skin tissues. The same PCR testing system was further confirmed with paraffin-embedded skin tissues samples from patients as well.

Results

The results of the study indicate promising outcomes for the four-pair primers system. It demonstrated 100% sensitivity in detecting M. marinum from purified cultures, including typical strains and nine clinical isolates, while achieving a specificity of 100%. This specificity was evidenced by the absence of PCR products from 12 bacterial species, 12 fungi species, and six other non-tuberculous mycobacterium (NTM) species. In the animal model, the PCR assay exhibited high detection efficacy for both infected fresh tissues and paraffin-embedded tissues, with a slight superiority observed in fresh tissues. However, the PCR assay exhibited high detection efficacy for clinical paraffin-embedded tissues. These findings collectively underscore the robust detection capabilities of our four-pair primers in both in vitro and in vivo settings.

Conclusion

A sensitive and highly specific rapid detection system has been successfully developed that can be used to detect M. marinum in both infected fresh tissues and paraffin-embedded tissues.

Genomic and phenotypic characterization of Mycobacterium tuberculosis' closest-related non-tuberculous mycobacteria

Four species of non-tuberculous mycobacteria (NTM) rated as biosafety level 1 or 2 (BSL-1/BSL-2) organisms and showing higher genomic similarity with Mycobacterium tuberculosis (Mtb) than previous comparator species Mycobacterium kansasii and Mycobacterium marinum were subjected to genomic and phenotypic characterization. These species named Mycobacterium decipiens, Mycobacterium lacus, Mycobacterium riyadhense, and Mycobacterium shinjukuense might represent "missing links" between low-virulent mycobacterial opportunists and the highly virulent obligate pathogen Mtb. We confirmed that M. decipiens is the closest NTM species to Mtb currently known and found that it has an optimal growth temperature of 32°C-35°C and not 37°C. M. decipiens showed resistance to rifampicin, isoniazid, and ethambutol, whereas M. lacus and M. riyadhense showed resistance to isoniazid and ethambutol. M. shinjukuense was sensitive to all three first-line TB drugs, and all four species were sensitive to bedaquiline, a third-generation anti-TB drug. Our results suggest these four NTM may be useful models for the identification and study of new anti-TB molecules, facilitated by their culture under non-BSL-3 conditions as compared to Mtb. M. riyadhense was the most virulent of the four species in cellular and mouse infection models. M. decipiens also multiplied in THP-1 cells at 35°C but was growth impaired at 37°C. Genomic comparisons showed that the espACD locus, essential for the secretion of ESX-1 proteins in Mtb, was present only in M. decipiens, which was able to secrete ESAT-6 and CFP-10, whereas secretion of these antigens varied in the other species, making the four species interesting examples for studying ESX-1 secretion mechanisms.IMPORTANCEIn this work, we investigated recently identified opportunistic mycobacterial pathogens that are genomically more closely related to Mycobacterium tuberculosis (Mtb) than previously used comparator species Mycobacterium kansasii and Mycobacterium marinum. We confirmed that Mycobacterium decipiens is the currently closest known species to the tubercle bacilli, represented by Mycobacterium canettii and Mtb strains. Surprisingly, the reference strain of Mycobacterium riyadhense (DSM 45176), which was purchased as a biosafety level 1 (BSL-1)-rated organism, was the most virulent of the four species in the tested cellular and mouse infection models, suggesting that a BSL-2 rating might be more appropriate for this strain than the current BSL-1 rating. Our work establishes the four NTM species as interesting study models to obtain new insights into the evolutionary mechanisms and phenotypic particularities of mycobacterial pathogens that likely have also impacted the evolution of the key pathogen Mtb.

Facile green synthesis of silver nanoparticles derived from the medicinal plant Clerodendrum serratum and its biological activity against Mycobacterium species

The emergence of multidrug-resistant mycobacterial strains is a significant crisis that has led to higher treatment failure rates and more toxic and expensive medications for tuberculosis (TB). The urgent need to develop novel therapeutics has galvanized research interest towards developing alternative antimicrobials such as silver nanoparticles (AgNPs). The current study focused on the anti-mycobacterial activity of green-synthesized AgNPs and its polyethylene glycol encapsulated derivative (PEG-AgNPs) with improved stability using the leaves extract of Clerodendrum serratum. Different characterization methods were used to analyze them. DLS analysis revealed a lower polydispersity index of PEG-AgNPs, suggesting a more uniform size distribution than that of AgNPs. The HR-TEM results revealed that the AgNPs and PEG-AgNPs have predominantly spherical shapes in the size range of 9-35 nm and 15-60 nm, respectively, while positive values of Zeta potential indicate their stability. FTIR-ATR analysis confirmed the presence of functional groups responsible for reducing and capping the bio-reduced AgNPs, whereas the XRD data established its crystalline nature. Impressively, the PEG-AgNPs exhibited maximum inhibitory activity against different Tubercular and Non-Tuberculous Mycobacterium species i.e., Mycobacterium smegmatis, Mycobacterium fortuitum and Mycobacterium marinum, relative to those of AgNPs and Linezolid. The flow cytometry assay showed that the anti-mycobacterial action was mediated by an increase in cell wall permeability. Notably, the results of AFM confirm their ability to inhibit mycobacterial biofilm significantly. We demonstrated the nontoxic nature of these AgNPs, explicated by the absence of hemolytic activity against human RBCs. Overall, the results suggest that PEG-AgNPs could offer a novel therapeutic approach with potential anti-mycobacterial activity and can overcome the limitations of existing TB therapies.

Review of methods for detection and characterization of non-tuberculous mycobacteria in aquatic organisms

Mycobacteriosis is an emerging and often lethal disease of aquatic organisms caused by several non-tuberculous mycobacteria (NTM) species. Early diagnosis of mycobacteriosis in aquaculture and aquatic settings is critical; however, clinical diagnoses and laboratory detection are challenging, and the available literature is scarce. In an attempt to fill the gap, here we review the most relevant approaches to detect and characterize mycobacteria in clinical specimens of aquatic organisms. Emphasis is given to recent advances in molecular methods used to differentiate NTM species spanning from targeted gene sequencing to next-generation sequencing. Further, given that there are major gaps in our understanding of the prevalence of the different NTM species, partially because of their distinct requirements for in vitro growth, we also reviewed the most relevant NTM species reported to cause disease in aquatic organisms and their specific in vitro growth conditions. We also highlight that traditional bacterial culture continues to be relevant for NTM identification, particularly in non-automated laboratories. However, for NTM species discrimination, a high level of accuracy can be achieved with MALDI-TOF MS and molecular approaches, especially targeted gene sequencing applied from clinical specimens or from pure NTM isolates.

Broad-Spectrum In Vitro Activity of Nα-Aroyl-N-Aryl-Phenylalanine Amides against Non-Tuberculous Mycobacteria and Comparative Analysis of RNA Polymerases

This study investigates the in vitro activity of Nα-aroyl-N-aryl-phenylalanine amides (AAPs), previously identified as antimycobacterial RNA polymerase (RNAP) inhibitors, against a panel of 25 non-tuberculous mycobacteria (NTM). The compounds, including the hit compound MMV688845, were selected based on their structural diversity and previously described activity against mycobacteria. Bacterial strains, including the M. abscessus complex, M. avium complex, and other clinically relevant NTM, were cultured and subjected to growth inhibition assays. The results demonstrate significant activity against the most common NTM pathogens from the M. abscessus and M. avium complexes. Variations in activity were observed against other NTM species, with for instance M. ulcerans displaying high susceptibility and M. xenopi and M. simiae resistance to AAPs. Comparative analysis of RNAP β and β' subunits across mycobacterial species revealed strain-specific polymorphisms, providing insights into differential compound susceptibility. While conservation of target structures was observed, differences in compound activity suggested influences beyond drug-target interactions. This study highlights the potential of AAPs as effective antimycobacterial agents and emphasizes the complex interplay between compound structure, bacterial genetics, and in vitro activity.

Syringaldehyde Exhibits Antibacterial and Antioxidant Activities against Mycobacterium marinum Infection

Tuberculosis (TB) is caused by infection with Mycobacterium tuberculosis (Mtb), which has a unique resistance to many antimicrobial agents. TB has emerged as a significant worldwide health issue because of the rise of multidrug-resistant strains causing drug-resistant TB (DR-TB). As a result, the development of new drugs or effective strategies is crucial for patients with TB. Mycobacterium marinum (Mm) and Mtb are both species of mycobacteria. In zebrafish, Mm proliferates and forms chronic granulomatous infections, which are similar to Mtb infections in lung tissue. Syringaldehyde (SA) is a member of the phenolic aldehyde family found in various plants. Here, we investigated its antioxidative and antibacterial properties in Mm-infected cells and zebrafish. Our results demonstrated that SA inhibits Mm-infected pulmonary epithelial cells and inhibits the proliferation of Mm in Mm-infected zebrafish, suggesting that SA provides an antibacterial effect during Mm infection. Further study demonstrated that supplementation with SA inhibits the production of malondialdehyde (MDA) and reactive oxygen species (ROS) and increases the levels of reduced glutathione (GSH) in Mm-infection-induced macrophages. SA inhibits the levels of MDA in Mm-infected zebrafish, suggesting that SA exerts antioxidative effects in vivo. Additionally, we found that SA promotes the expression of NRF2/HO-1/NQO-1 and the activation of the AMPK-α1/AKT/GSK-3β signaling pathway. In summary, our data demonstrated that SA exerts antioxidative and antibacterial effects during Mm infection both in vivo and in vitro and that the antioxidative effects of SA may be due to the regulation of NRF2/HO-1/NQO-1 and the AMPK-α1/AKT/GSK-3β signaling pathway.

A Review of the Industrial Importance, Common Bacterial Diseases, and Zoonotic Risks of Freshwater Aquarium Fish

Background: The ever-increasing popularity of home aquariums, most often involving freshwater varieties, has exploded in recent years partially due to the Coronavirus pandemic and related to stay-at-home public health precautions for social distancing. With this ever-increasing popularity of aquariums as a hobby, and whether this involves freshwater or marine fish species, a number of important economic, ecological, and public health issues arise for both fish and hobbyists alike. Materials and Methods: This review highlights the history and genesis of aquariums as both a hobby and an important economic factor (industrial, commercial) for many countries on a global basis. Types of aquarium fish are described, and culture conditions leading to homeostasis in aquatic environments are detailed. When these conditions are not met and aquatic systems are out of balance, the disease can result due to stressed fish. Results: Major bacterial diseases associated with freshwater aquarium fish are reviewed, as are potential human infections related to the care and maintenance of home aquaria. Conclusion: Besides, scientific information was also combined with the false facts of hobbyists who tried to identify and treat diseases during an outbreak in the aquarium. Finally, unresolved issues and important misconceptions regarding the field are discussed.

Application of Genomic Epidemiology of Pathogens to Farmed Yellowtail Fish Mycobacteriosis in Kyushu, Japan

To investigate mycobacterial cases of farmed yellowtail fish in coastal areas of western Japan (Kagoshima, Kyushu), where aquaculture fisheries are active, Mycobacterium pseudoshottsii, the causative agent, was isolated from six neighboring fishing ports in 2012 and 2013. A phylogenetic ana-lysis revealed that the strains isolated from one fishing port were closely related to those isolated from other regions of Japan, suggesting the nationwide spread of a single strain. However, strains from Japan were phylogenetically distinct from those from the Mediterranean and the United States; therefore, worldwide transmission was not observed based on the limited data obtained on the strains exami-ned in this study. The present results demonstrate that a bacterial genomic ana-lysis of infected cases, a mole-cular epidemiology strategy for public health, provides useful data for estimating the prevalence and transmission pathways of M. pseudoshottsii in farmed fish. A bacterial genome ana-lysis of strains, such as that performed herein, may play an important role in monitoring the prevalence of this pathogen in fish farms and possible epidemics in the future as a result of international traffic, logistics, and trade in fisheries.

Environmental Sources and Transmission of Nontuberculous Mycobacteria

The field of environmental nontuberculous mycobacteria (NTM) is benefiting from a new era of genomics that has catapulted our understanding of preferred niches, transmission, and outbreak investigations. The ability to forecast environmental features that promote or reduce environmental NTM prevalence will greatly improve with coordinated environmental sampling and by elevating the necessity for uniform disease notifications. Studies that synergize environmental biology, isolate notifications, and comparative genomics in prospective, longitudinal studies, particularly during climate changes and weather events, will be useful to solve longstanding NTM public health quandaries.

The role of marine pollution on the emergence of fish bacterial diseases

Marine pollution and bacterial disease outbreaks are two closely related dilemmas that impact marine fish production from fisheries and mariculture. Oil, heavy metals, agrochemicals, sewage, medical wastes, plastics, algal blooms, atmospheric pollutants, mariculture-related pollutants, as well as thermal and noise pollution are the most threatening marine pollutants. The release of these pollutants into the marine aquatic environment leads to significant ecological degradation and a range of non-infectious disorders in fish. Marine pollutants trigger numerous fish bacterial diseases by increasing microbial multiplication in the aquatic environment and suppressing fish immune defense mechanisms. The greater part of these microorganisms is naturally occurring in the aquatic environment. Most disease outbreaks are caused by opportunistic bacterial agents that attack stressed fish. Some infections are more serious and occur in the absence of environmental stressors. Gram-negative bacteria are the most frequent causes of these epizootics, while gram-positive bacterial agents rank second on the critical pathogens list. Vibrio spp., Photobacterium damselae subsp. Piscicida, Tenacibaculum maritimum, Edwardsiella spp., Streptococcus spp., Renibacterium salmoninarum, Pseudomonas spp., Aeromonas spp., and Mycobacterium spp. Are the most dangerous pathogens that attack fish in polluted marine aquatic environments. Effective management strategies and stringent regulations are required to prevent or mitigate the impacts of marine pollutants on aquatic animal health. This review will increase stakeholder awareness about marine pollutants and their impacts on aquatic animal health. It will support competent authorities in developing effective management strategies to mitigate marine pollution, promote the sustainability of commercial marine fisheries, and protect aquatic animal health.

Current risks of microbial infections in fish and their prevention methods: A review

A fast-expanding sector of agriculture worldwide is aquaculture. The production of fish internationally accounts for around 44 % of the total. Even though the aquaculture environment presents several difficulties, the current development in aquaculture production comes with an increase in infectious diseases, which significantly impacts the production, profitability, and sustainability of the worldwide aquaculture business. Many infectious agents, such as bacteria, viruses, fungi and parasites are causative agents for fish infections. Most infectious diseases found in all types of fish like marine water, freshwater and ornamental fishes are caused by bacteria, with many of them serving as secondary opportunistic invaders that attack sick animals by affecting their natural host immunity. To overcome this, addressing health issues based on methods that have been scientifically verified and advised will help lessen the effects of fish disease. This review aims to highlight some of the common microbial-infecting agents of fish in all types of aquatic systems and their effective methods for preventing infections in aquaculture.

Rapid diagnosis of Mycobacterium marinum infection using targeted nanopore sequencing: a case report

Mycobacterium marinum (M. marinum) is a non-tuberculous mycobacterium (NTM) that can cause infectious diseases in aquatic animals and humans. Culture-based pathogen detection is the gold standard for diagnosing NTM infection. However, this method is time-consuming and has low positivity rates for fastidious organisms. Oxford Nanopore MinION sequencing is an emerging third-generation sequencing technology that can sequence DNA or RNA directly in a culture-independent manner and offers rapid microbial identification. Further benefits include low cost, short turnaround time, long read lengths, and small equipment size. Nanopore sequencing plays a crucial role in assessing drug resistance, clinical identification of microbes, and monitoring infectious diseases. Some reports on Mycobacterium tuberculosis (MTB) using nanopore sequencing have been published, however, there are few reports on NTM, such as M. marinum. Here, we report the use of nanopore sequencing for the diagnosis of M. marinum.

Bacterial diseases in marine fish species: current trends and future prospects in disease management

The fisheries sub-sector of aquaculture-i.e., the pisciculture industry, contributes significantly to a country's economy, employing a sizable proportion of the population. It also makes important contributions to household food security because the current demand for animal protein cannot be fulfilled by harvesting wild fish from riverines, lakes, dams, and oceans. For good pond management techniques and sustaining fish health, the fisherfolk, and the industry require well-established regulatory structures, efficient disease management strategies, and other extended services. In rearing marine fish, infections resulting from disease outbreaks are a weighty concern because they can cause considerable economic loss due to morbidity and mortality. Consequently, to find effective solutions for the prevention and control of the major diseases limiting fish production in aquaculture, multidisciplinary studies on the traits of potential fish pathogens, the biology of the fish as hosts, and an adequate understanding of the global environmental factors are fundamental. This review highlights the various bacterial diseases and their causative pathogens prevalent in the pisciculture industry and the current solutions while emphasising marine fish species. Given that preexisting methods are known to have several disadvantages, other sustainable alternatives like antimicrobial peptides, synthetic peptides, probiotics, and medicinal treatments have emerged to be an enormous potential solution to these challenges.

Treatment of non-tuberculosis mycobacteria skin infections

Non-tuberculosis mycobacteria (NTM) skin infections have become increasingly prevalent in recent years, presenting a unique challenge in clinical management. This review explored the complexities of NTM infections localized to the superficial tissues and provided valuable insights into the optimal therapeutic strategies. The antibiotic selection should base on NTM species and their susceptibility profiles. It is recommended to adopt a comprehensive approach that considers the unique characteristics of superficial tissues to improve treatment effectiveness and reduce the incidence of adverse reactions, infection recurrence, and treatment failure. Infection control measures, patient education, and close monitoring should complement the treatment strategies to achieve favorable outcomes in managing NTM skin infections. Further efforts are warranted to elucidate factors and mechanisms contributing to treatment resistance and relapse. Future research should focus on exploring novel treatment options, innovative drug development/delivery platforms, and precise methodologies for determining therapeutic duration. Longitudinal studies are also needed to assess the long-term safety profiles of the integrated approaches.

Photodynamic therapy: a new approach to the treatment of Nontuberculous Mycobacterial skin and soft tissue infections

Nontuberculous mycobacterial skin and soft tissue infections are rising and are causing social concern due to the growth of cosmetic dermatology and immune-compromised populations. For the treatment of nontuberculous mycobacteria, several novel strategies have been investigated. One of them, photodynamic therapy, is a recently developed therapeutic strategy that has shown promise in managing nontuberculous mycobacterial skin and soft tissue infections. In this review, we first present an overview of the current status of the therapy and then summarize and analyze the cases of photodynamic therapy used to treat nontuberculous mycobacterial skin and soft tissue infections. We also discussed the feasibility of photodynamic therapy for treating nontuberculous mycobacterial skin soft tissue infections and the related mechanisms, providing a potential new option for clinical treatment.

Mycobacterium marinum: A Case-Based Narrative Review of Diagnosis and Management

Skin and soft tissue infections caused by non-tuberculous mycobacteria are occurring more frequently in recent years. However, chronic skin and soft tissue lesions present a challenge for clinicians, as the diagnostic work-up and definitive diagnosis require knowledge and available laboratory resources. We present here the case of a 66-year-old male patient who presented with painful abscess-like nodules on his right hand and forearm, which worsened after treatment with an anti-TNF-a agent. The fluid specimen taken from the lesion was positive for mycobacteria according to the acid-fast stain. Mycobacterium marinum was identified, first by next-generation sequencing and finally grown on culture, after eight weeks. Acknowledging the complexity of diagnosing and managing infections by non-tuberculous mycobacteria, and especially Mycobacterium marinum, we provide a review of the current epidemiology, clinical characteristics, diagnosis and management of Mycobacterium marinum infection.

Adenitis as Initial Mycobacterium marinum Presentation

Mycobacterium marinum is a ubiquitous and opportunist agent that may cause infections related to water activities in humans. It causes mainly skin and soft tissue infections, and other forms of presentation are uncommon. A 27-year-old man presented to the Emergency Department of a tertiary hospital due to a cervical foreign-body sensation that evolved into right cervical swelling and consumption symptoms. He was a waiter on a cruise in the Douro river. Weeks after the initial presentation, the diagnosis of Mycobacterium marinum infection was made by positive nucleic acid amplification tests (NAAT) in tissues obtained by excisional biopsy of cervical adenopathy. Treatment with rifampicin and clarithromycin was started. The symptoms improved, and there was a decrease in the adenopathy number and size. Although Mycobacterium marinum adenitis as initial presentation of the disease is rare, the identification of the agent by NAAT and favorable response to treatment supported the diagnosis.

Ruxolitinib Treatment During Myelofibrosis Leads to Cutaneous Mycobacterium marinum Infection: A Case Report

Mycobacterium marinum is an atypical bacterium, and skin infections caused by it are relatively rare, usually occurring in workers engaged in seafood processing and housewives who clean and prepare fish for consumption. The infection often occurs after the skin is punctured by fish scales, spines, etc. The JAK/STAT signaling pathway is closely related to the human immune response to infections. Therefore, JAK inhibitors may induce and exacerbate various infections in clinical practice. This article reports a case of mycobacterium marinum skin infection in the left upper limb of a female patient with chronic idiopathic myelofibrosis during treatment with ruxolitinib. The patient denied being punctured or scratched by fish scales or spines. Clinical manifestations included multiple infiltrative erythemas and subcutaneous nodules in the thumb and forearm. Histopathological examination showed infiltration of mixed acute and chronic inflammatory cells in the subcutaneous tissue. The diagnosis was ultimately confirmed by NGS sequencing. The patient was cured after taking moxifloxacin and clarithromycin for 10 months. Infection is a common adverse reaction of JAK inhibitors, but no literature has reported on mycobacterium marinum skin infections occurring during JAK inhibitor treatment, which is relatively rare. As the clinical application of JAK inhibitors becomes more widespread, the skin infections they cause may present in various forms and require the attention of clinicians.

Sorbed environmental contaminants increase the harmful effects of microplastics in adult zebrafish, Danio rerio

Aquatic animals ingest Microplastics (MPs) which have the potential to affect the uptake and bioavailability of sorbed co-contaminants. However, the effects on living organisms still need to be properly understood. The present study was designed to assess the combined effects of MPs and environmental contaminants on zebrafish (Danio rerio) health and behavior. Adult specimens were fed according to three different protocols: 1) untreated food (Control group); 2) food supplemented with 0.4 mg/L pristine polyethylene-MPs (PE-MPs; 0.1-0.3 mm diameter) (PEv group); 3) food supplemented with 0.4 mg/L PE-MPs previously incubated (PEi group) for 2 months in seawater. Analysis of contaminants in PEi detected trace elements, such as lead and copper. After 15 days of exposure, zebrafish underwent behavioral analysis and were then dissected to sample gills and intestine for histology, and the latter also for microbiome analysis. Occurrence of PEv and PEi in the intestine and contaminants in the fish carcass were analyzed. Both PEv- and PEi-administered fish differed from controls in the assays performed, but PEi produced more harmful effects in most instances. Overall, MPs after environmental exposure revealed higher potential to alter fish health through combined effects (e.g. proportion of microplastics, pollutants and/or microorganisms).

Lower Extremity Nodules After Spelunking in Mexico

Mycobacterium marinum is a non-tuberculous mycobacterium that presents as a nodular granulomatous disease. The bacillus can infect humans when broken skin is exposed to a contaminated aquatic environment. M. marinum infections are usually isolated to the skin and soft tissues and can spread in a lymphatic distribution. A 26-year-old male cut his right ankle while spelunking in Tulum, Mexico. He presented to his primary care physician three months after he sustained the laceration with a nonhealing wound on the right lateral posterior ankle. Examination of the lesion demonstrated erythematous, violaceous, and hyperpigmented indurated plaques with satellite lesions noted at the right medial, posterior, and lateral ankle. The lesion characteristics raised initial suspicion for an invasive fungal infection. Biopsy of the lesion demonstrated epidermal ulceration covered by neutrophilic serum, marked underlying dermal acute inflammation, and granulation tissue. A mild perivascular, predominantly lymphocytic infiltrate was present in the deep dermis with no evidence of granuloma. Acid-fast bacilli culture plated onto chocolate agar confirmed the species M. marinum.

Molecular epidemiology of nontuberculous mycobacteria isolated from tuberculosis-suspected patients

It is a growing problem around the world to deal with nontuberculous mycobacteria infection (NTM), but its clinical significance is still largely unknown. This study aims to investigate the epidemiology of NTM infections from various clinical samples and determine their clinical significance. From December 2020 to December 2021, 6125 clinical samples were collected. In addition to phenotypic detection, genotypic detection through multilocus sequence typing (hsp65, rpoB, and 16S rDNA genes) and sequencing was also conducted. Records of patients were consulted for clinical information, such as symptoms and radiological findings. Of the 6,125 patients, 351 (5.7%) were positive for acid-fast bacteria (AFB). Out of 351 AFB, 289 (82.3%) and 62 (17.7%) subjects were identified as M. tuberculosis complex (MTC) and NTM strains, respectively. Isolates of Mycobacterium simiae and M. fortuitum were the most frequent, followed by isolates of M. kansasii and M. marinum. We also isolated M. chelonae, M. canariasense, and M. jacuzzii, which are rarely reported. Symptoms (P = 0.048), radiographic findings (P = 0.013), and gender (P = 0.039) were associated with NTM isolates. M. Fortuitum, M. simiae, and M. kansasii presented with bronchiectasis, infiltration, and cavitary lesions most frequently, while cough was the most common symptom. In conclusion, Mycobacterium simiae and M. fortuitum were presented in seventeen and twelve NTM isolates from the collected samples. There is evidence that NTM infections in endemic settings may contribute to the dissemination of various diseases and the control of tuberculosis. In spite of this, further research is needed to evaluate the clinical significance of NTM isolates.

Current treatment options for Mycobacterium marinum cutaneous infections

INTRODUCTION

Mycobacterium marinum is a slowly growing photochromogenic nontuberculous mycobacterium that has special growth characteristics. It causes a uniquely human disease, a cutaneous syndrome named fish tank granuloma or swimming pool granuloma because of the strong epidemiological links with water. The treatment of this disease involves the use of different antimicrobials alone and in combination, depending on the severity of the disease. The antibiotics most frequently used are macrolides, tetracyclines, cotrimoxazole, quinolones, aminoglycosides, rifamycins, and ethambutol. Other approaches include the use of surgery in some cases. New treatment options, like new antibiotics, phage therapy, phototherapy, and others are currently being developed with good in vitro experimental results. In any case, the disease is usually a mild one, and the outcome is good in most of the treated patients.

AREAS COVERED

We have searched the literature for treatment schemes and drugs used for treatment of M. marinum disease, as well as other therapeutic options.

EXPERT OPINION

Medical treatment is the most recommended approach option, as M. marinum is usually susceptible to tetracyclines, quinolones, macrolides, cotrimoxazole, and some tuberculostatic drugs, usually used in a combined therapeutic scheme. Surgical treatment is an option that can be curative and diagnostic in small lesions.

Complete Genome Sequence of Mycobacterium marinum Strain 050012 Isolated from Infected Skin Tissue

We report the complete genome sequence of a Mycobacterium marinum strain, which was isolated from skin tissue of a wound infection. This strain was subjected to short- and long-read sequencing. Its complete genome contains a single 6,393,703-bp circular chromosome. Phylogenomic analysis of all M. marinum genomes assigned this strain to cluster I.

First identification of mycobacteriosis in Atlantic mackerel (Scomber scombrus)

Mycobacterium infection in fish is a well-known disease problem globally, mainly in the farming of ornamental fish or fish for food. Less is known about the prevalence, distribution and the effects such infections have on wild fish species. Presumptive mycobacteriosis has previously been observed in Atlantic mackerel (Scomber scombrus). Since 2018, there has been an increase in reports of granulomatous kidney disease in Atlantic mackerel with the suspicion of this being mycobacteriosis. A total of six individuals were sent to the Institute of Marine Research for further examination. They were caught in the Nordic Sea by either commercial fishing vessels or during the International Ecosystem Summer Survey in the Nordic Seas (IESSNS research cruise) between 2018 and 2020. Samples for both histological and molecular analysis were collected. Here, we detect a likely novel Mycobacterium species in tissue samples from Atlantic mackerel with this condition, on the basis of rDNA and protein gene sequences. The same unnamed bacterium seems to have been found in some Pacific marine fishes. The macroscopic and histological manifestation of the disease is described. Over the past years, there has been an increase in reports of mycobacteriosis worldwide and climate change has been suggested as one of the driving forces as these bacteria prefer warm water.

Core single nucleotide polymorphism analysis reveals transmission of Mycobacterium marinum between animal and environmental sources in two aquaria

Mycobacterium marinum is a slow-growing, photochromogenic nontuberculous mycobacterium, which can cause mycobacteriosis in various animals, including humans. Several cases of fish mycobacteriosis have been reported to date. Mycobacterium marinum has also been isolated from aquatic environmental sources such as water, sand, biofilms, and plants in the natural environments. Hence, we hypothesized that a wide variety of sources could be involved in the transmission of M. marinum. In this study, we tested this hypothesis by isolating M. marinum from various sources such as fish, invertebrates, seagrass, periphytons, biofilms, sand, and/or water in two aquaria in Japan and conducting a phylogenetic analysis based on single-nucleotide polymorphisms (SNPs) using whole-genome sequences of the isolated strains. The analysis revealed that the strains from animal and environmental sources belonged to the same clusters. This molecular-based study epidemiologically confirmed that various sources, including fish, invertebrates, and environmental sources, could be involved in transmission of M. marinum in a closed-rearing environment. This is the first report where M. marinum was isolated from different sources, and various transmission routes were confirmed in actual cases, which provided essential information to improve the epidemiology of M. marinum.

A new pathogenic isolate of Kocuria kristinae identified for the first time in the marine fish Larimichthys crocea

In recent years, new emerging pathogenic microorganisms have frequently appeared in animals, including marine fish, possibly due to climate change, anthropogenic activities, and even cross-species transmission of pathogenic microorganisms among animals or between animals and humans, which poses a serious issue for preventive medicine. In this study, a bacterium was clearly characterized among 64 isolates from the gills of diseased large yellow croaker Larimichthys crocea that were raised in marine aquaculture. This strain was identified as K. kristinae by biochemical tests with a VITEK 2.0 analysis system and 16S rRNA sequencing and named K. kristinae_LC. The potential genes that might encode virulence-factors were widely screened through sequence analysis of the whole genome of K. kristinae_LC. Many genes involved in the two-component system and drug-resistance were also annotated. In addition, 104 unique genes in K. kristinae_LC were identified by pan genome analysis with the genomes of this strain from five different origins (woodpecker, medical resource, environment, and marine sponge reef) and the analysis results demonstrated that their predicted functions might be associated with adaptation to living conditions such as higher salinity, complex marine biomes, and low temperature. A significant difference in genomic organization was found among the K. kristinae strains that might be related to their hosts living in different environments. The animal regression test for this new bacterial isolate was carried out using L. crocea, and the results showed that this bacterium could cause the death of L. crocea and that the fish mortality was dose-dependent within 5 days post infection, indicating the pathogenicity of K. kristinae_LC to marine fish. Since K. kristinae has been reported as a pathogen for humans and bovines, in our study, we revealed a new isolate of K. kristinae_LC from marine fish for the first time, suggesting the potentiality of cross-species transmission among animals or from marine animals to humans, from which we would gain insight to help in future public prevention strategies for new emerging pathogens.

Mycobacterium marinum: A Challenging Cause of Protracted Tenosynovitis

Mycobacterium marinum infections are rare, and they can be difficult to diagnose and treat. This may lead to further spread of the infection and complications, such as tenosynovitis, pyomyositis, and osteomyelitis. A 40-year-old previously healthy man presented with tenosynovitis of the extensor tendons on the second phalanx of his right hand. He was initially treated with steroid injections without any effect. Followingly, ulceration and an abscess developed on the dorsal site of the hand. At this point, it came to the physician's knowledge that the patient had been cleaning an aquarium before onset of symptoms. After progression to massive tenosynovitis, the patient was admitted and underwent multiple surgical debridements. Briefly, after the first surgery, an interferon-γ release assay was positive, and treatment for M. marinum with rifampicin and azithromycin was initiated after eight months of symptoms. Later, a surgical biopsy showed acid-fast bacilli, and a polymerase chain reaction confirmed the diagnosis of M. marinum. In this case story, we highlight the difficulties of diagnosing and managing this complicated infection, describe the considerable morbidity associated with it, and suggest that local tissue concentrations could be useful to improve clinical outcomes, as these concentrations are potentially suboptimal.

Galleria mellonella-intracellular bacteria pathogen infection models: the ins and outs

Galleria mellonella (greater wax moth) larvae are used widely as surrogate infectious disease models, due to ease of use and the presence of an innate immune system functionally similar to that of vertebrates. Here, we review G. mellonella-human intracellular bacteria pathogen infection models from the genera Burkholderia, Coxiella, Francisella, Listeria, and Mycobacterium. For all genera, G. mellonella use has increased understanding of host-bacterial interactive biology, particularly through studies comparing the virulence of closely related species and/or wild-type versus mutant pairs. In many cases, virulence in G. mellonella mirrors that found in mammalian infection models, although it is unclear whether the pathogenic mechanisms are the same. The use of G. mellonella larvae has speeded up in vivo efficacy and toxicity testing of novel antimicrobials to treat infections caused by intracellular bacteria: an area that will expand since the FDA no longer requires animal testing for licensure. Further use of G. mellonella-intracellular bacteria infection models will be driven by advances in G. mellonella genetics, imaging, metabolomics, proteomics, and transcriptomic methodologies, alongside the development and accessibility of reagents to quantify immune markers, all of which will be underpinned by a fully annotated genome.

Bacterial Pathogenesis in Various Fish Diseases: Recent Advances and Specific Challenges in Vaccine Development

Aquaculture is a fast-growing food sector but is plagued by a plethora of bacterial pathogens that infect fish. The rearing of fish at high population densities in aquaculture facilities makes them highly susceptible to disease outbreaks, which can cause significant economic loss. Thus, immunity development in fish through vaccination against various pathogens of economically important aquaculture species has been extensively studied and has been largely accepted as a reliable method for preventing infections. Vaccination studies in aquaculture systems are strategically associated with the economically and environmentally sustainable management of aquaculture production worldwide. Historically, most licensed fish vaccines have been developed as inactivated pathogens combined with adjuvants and provided via immersion or injection. In comparison, live vaccines can simulate a whole pathogenic illness and elicit a strong immune response, making them better suited for oral or immersion-based therapy methods to control diseases. Advanced approaches in vaccine development involve targeting specific pathogenic components, including the use of recombinant genes and proteins. Vaccines produced using these techniques, some of which are currently commercially available, appear to elicit and promote higher levels of immunity than conventional fish vaccines. These technological advancements are promising for developing sustainable production processes for commercially important aquatic species. In this review, we explore the multitude of studies on fish bacterial pathogens undertaken in the last decade as well as the recent advances in vaccine development for aquaculture.

Rheumatoid arthritis caused by non-tuberculous mycobacteria infection

A 72-year-old Japanese woman had right digital flexor tenosynovitis with a non-tuberculous mycobacteria (NTM) infection, which was identified as Mycobacterium marinum in culture. She had been treated at another hospital with clarithromycin, rifampicin, and ethambutol for the non-tuberculous tenosynovitis. However, the swelling of her right hand worsened, and 5 months later, her left hand swelled and she exhibited symmetrical arthritis. Blood tests detected elevated serum C-reactive protein and rheumatoid factor positivity. Although rheumatoid arthritis (RA) was suspected and corticosteroid treatment was started, she came to our hospital because of the insufficient treatment effect. Musculoskeletal ultrasonography showed intra-articular and peritendinous power Doppler signal-positive symmetrical synovitis. A contrast-enhanced magnetic resonance imaging (MRI) evaluation of the left hand without NTM tenosynovitis revealed findings of inflammatory synovitis accompanied by bone marrow oedema. We diagnosed RA and started treatment with weekly low-dose methotrexate pulses and 2 weeks of tocilizumab administration; her symptoms then disappeared within 2 months. This is a rare case of RA manifested with NTM-associated arthritis.

Ocular pathology in aquarium fish with a focus on the Syngnathidae and Apogonidae families

This study catalogued ocular pathology in fish histopathology submissions to a specialist diagnostic service and investigated associations with species and systemic disease, with a focus on species of conservation interest. Cross-tabulations and Fisher's exact tests were used to identify associations among the variables and results are reported as prevalence ratios (PRs) with 95% confidence intervals (CI). Of 12,488 reports reviewed, ocular histology examination was available for 4,572 submissions, in which histopathological ocular lesions were identified in 18% (813/4572). Most diagnoses (701/813; 87%) were in marine fish. Inflammatory conditions were most common (608/813; 75%), with identification of a bacterial aetiology in 42% (255/608) and a parasitic aetiology in 30% (183/608). Most bacterial infections were due to mycobacteriosis (153/255; 60%) and most parasitic infections were due to scuticociliatosis (114/184; 62%). The Syngnathidae, Centriscidae and Cichlidae families were each more likely than all other families combined to be diagnosed with ocular manifestations of mycobacteriosis (PRs = 2.6, 4.4 and 2.9, respectively, P <0.0001 for each). The Syngnathidae were also more likely to be diagnosed with ocular scuticociliatosis (PR = 1.9, P <0.0001). Fifty-four percent (39/72) of ocular mycobacteriosis and 38% (9/24) of gas bubble disease cases affected threatened or near threatened Syngnathidae species. The Apogonidae were more likely than any other family to have ocular iridovirus (PR = 10.3, 95% CI = 5.5-19.4, P <0.0001) and neoplasia (PR = 8.2, 95% CI = 4.2-16.3, P <0.0001). The endangered Banggai cardinalfish (Pterapogon kauderni) accounted for 13/15 ocular iridovirus and 16/18 mycobacteriosis cases in this family. All cases of neoplasia in the Apogonidae occurred in pajama cardinalfish (Sphaeramia nematoptera). These results should inform clinical diagnosis of ocular disease in aquarium fish and influence training for aquarists, highlighting ocular pathology as a potential early warning of systemic disease. The findings also have direct/indirect consequences for the welfare and conservation of some of these popular flagship fish species.

A case of mycobacteriosis associated with Mycobacterium pseudoshottsii in aquarium-reared fish in Japan

In 2019, several aquarium-reared fish died at a sea life park in Japan. Necropsy revealed micronodules on the spleen in the dotted gizzard shad (Konosirus punctatus). Seven of 16 fish exhibited microscopic multifocal granulomas associated with acid-fast bacilli in the spleen, kidney, liver, alimentary tract, mesentery, gills, and/or heart. Bacterial cultures yielded isolates from the dotted gizzard shad and a Japanese sardine (Sardinops melanostictus). Microbiological and molecular biological examinations revealed the isolates as Mycobacterium pseudoshottsii. To our knowledge, this is the first isolation of M. pseudoshottsii from aquarium-reared fish.

Mycobacterium marinum: A brief update for clinical purposes

Mycobacterium marinum (M. marinum) is a free-living, slow grower nontuberculous mycobacteria (NTM), strictly related to Mycobacterium tuberculosis, that causes disease in fresh and saltwater fish and it is one of the causes of extra-pulmonary mycobacterial infections, ranging in human from simple cutaneous lesions to disseminated forms in immunocompromised hosts. The first human cases of M. marinum infection were reported from skin lesions of swimmers in a contaminated pool, in 1951, in Sweden by Norden and Linell. Two conditions are required to develop M. marinum infection: (1) skin solution of continuity and (2) exposure to the contaminated water or direct contact with fish or shellfish. The so-called "fish-tank granuloma", the most frequent cutaneous manifestation of M. marinum infection, is characterized by a single papulonodular, verrucose and/or ulcerated granulomatous lesion in the inoculum site. Careful patient's history collection, high clinical suspicion and appropriate sample (e.g. cutaneous biopsy) for microbiological culture are crucial for a timely diagnosis. The treatment is not standardized yet and relies on administration of two active antimycobacterial agents, always guided by antimicrobial susceptibility test on culture, with macrolides and rifampin as pivotal drugs, as well as prompt surgery when feasible. In this narrative review, we provide to Clinicians an updated report of epidemiology, microbiological characteristics, clinical presentation, diagnosis, and management of M. marinum infection.

Mycobacterium marinum Cutaneous Infection: A Series of Three Cases and Literature Review

Mycobacterium marinum is a non-tuberculous mycobacteria present in natural and non-chlorinated bodies of water. It is a known fish pathogen but can also cause human disease. It usually causes cutaneous lesions but in rare cases may originate more invasive diseases with the involvement of deep structures. We describe three cases of patients with cutaneous infection by M. marinum evaluated in a tertiary care center, two with confirmed infection and one with a presumptive diagnosis based on clinical and epidemiological features. A brief bibliographic review of M. marinum infections is then presented to support the theme. We aim to alert one to the difficulties in establishing the correct diagnosis of this infection, emphasize the importance of a high degree of suspicion for its identification, and review the therapeutic management options.

Modified aluminosilicates display antibacterial activity against nontuberculous mycobacteria and adsorb mycolactone and Mycobacterium ulcerans in vitro

Mycobacterium ulcerans (MU) infection of skin and soft tissue leads to chronic skin ulceration known as Buruli ulcer. MU releases a lipid-like toxin, mycolactone, that diffuses into the tissue, effecting disease through localized tissue necrosis and immunosuppression. Cutaneous Buruli ulcer wounds slowly advance from a painless pre-ulcerative stage to an ulcerative lesion, leading to disparities in the timing of medical intervention and treatment outcomes. Novel Buruli ulcer wound management solutions could complement and supplement systemically administered antimicrobials and reduce time to healing. Capitalizing on nanopore structure, adsorption, and exchange capacities, aluminosilicate nanozeolites (nZeos) and geopolymers (GPs) were developed and investigated in the context of therapeutics for mycobacterial disease ulcerative wound care. nZeos were ion exchanged with copper or silver to assess the antimicrobial activity against MU and Mycobacterium marinum, a rapid growing, genetic ancestor of MU that also causes skin and soft tissue infections. Silver- and copper-exchanged nZeos were bactericidal against MU, while only silver-exchanged nZeos killed M. marinum. To mediate adsorption at a biological scale, GPs with different pore sizes and altered surface modifications were generated and assessed for the ability to adsorb MU and mycolactone. Macroporous GPs with and without stearic acid modification equivalently adsorbed MU cells, while mesoporous GPs with stearic acid adsorbed mycolactone toxin significantly better than mesoporous GPs or GPs modified with phenyltriethoxysilane (PTES). In cytotoxicity assays, Cu-nZeos lacked toxicity against Detroit 551, U-937, and WM-115 cells. GPs demonstrated limited cytotoxicity in Detroit 551 and WM-115, but produced time-dependent toxicity in U-937 cells. With their large surface area and adsorptive capacities, aluminosilicates nZeos and GPs may be modified and developed to support conventional BU wound care. Topical application of nZeos and GPs could kill MU within the cutaneous wound environment and physically remove MU and mycolactone with wound dressing changes, thereby improving wound healing and overall patient outcomes.

Draft Genome Sequences of 25 Mycobacterium marinum Strains Isolated from Animals and Environmental Components in Aquaria and an Aquaculture Farm

Mycobacterium marinum is a ubiquitous nontuberculous mycobacterium that causes infections in various animals. Here, we report the annotated draft genome sequences of 25 strains isolated from vertebrates, invertebrates, and environmental components in aquaria and an aquaculture farm in Japan, sampled between 2015 and 2020.

Host–Pathogen Interactions of Marine Gram-Positive Bacteria

Simple Summary

Complex interactions between marine Gram-positive pathogens and fish hosts in the marine environment can result in diseases of economically important finfish, which cause economic losses in the aquaculture industry. Understanding how these pathogens interact with the fish host and generate disease will contribute to efficient prophylactic measures and treatments. To our knowledge, there are no systematic reviews on marine Gram-positive pathogens. Therefore, here we reviewed the host–pathogen interactions of marine Gram-positive pathogens from the pathogen-centric and host-centric points of view.

Abstract

Marine Gram-positive bacterial pathogens, including Renibacterium salmoninarum, Mycobacterium marinum, Nocardia seriolae, Lactococcus garvieae, and Streptococcus spp. cause economic losses in marine fish aquaculture worldwide. Comprehensive information on these pathogens and their dynamic interactions with their respective fish–host systems are critical to developing effective prophylactic measures and treatments. While much is known about bacterial virulence and fish immune response, it is necessary to synthesize the knowledge in terms of host–pathogen interactions as a centerpiece to establish a crucial connection between the intricate details of marine Gram-positive pathogens and their fish hosts. Therefore, this review provides a holistic view and discusses the different stages of the host–pathogen interactions of marine Gram-positive pathogens. Gram-positive pathogens can invade fish tissues, evade the fish defenses, proliferate in the host system, and modulate the fish immune response. Marine Gram-positive pathogens have a unique set of virulence factors that facilitate adhesion (e.g., adhesins, hemagglutination activity, sortase, and capsules), invasion (e.g., toxins, hemolysins/cytolysins, the type VII secretion system, and immune-suppressive proteins), evasion (e.g., free radical quenching, actin-based motility, and the inhibition of phagolysosomal fusion), and proliferation and survival (e.g., heme utilization and siderophore-mediated iron acquisition systems) in the fish host. After infection, the fish host initiates specific innate and adaptive immune responses according to the extracellular or intracellular mechanism of infection. Although efforts have continued to be made in understanding the complex interplay at the host–pathogen interface, integrated omics-based investigations targeting host–pathogen–marine environment interactions hold promise for future research.