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Mycobacterium marinum is an opportunistic pathogen inducing infection in fresh and marine water fish. This pathogen causes necrotizing granuloma like tuberculosis, morbidity and mortality in fish. The cell wall-associated lipid phthiocerol dimycocerosates, phenolic glycolipids and ESAT-6 secretion system 1 (ESX-1) are the conserved virulence determinant of the organism. Human infections with Mycobacterium marinum hypothetically are classified into four clinical categories (type I-type IV) and have been associated with the exposure of damaged skin to polluted water from fish pools or contacting objects contaminated with infected fish. Fish mycobacteriosis is clinically manifested and characterized in man by purple painless nodules, liable to develop into superficial crusting ulceration with scar formation. Early laboratory diagnosis of M. marinum including histopathology, culture and PCR is essential and critical as the clinical response to antibiotics requires months to be attained. The pathogenicity and virulence determinants of M. marinum need to be thoroughly and comprehensively investigated and understood. In spite of accumulating information on this pathogen, the different relevant data should be compared, connected and globally compiled. This article is reviewing the epidemiology, virulence factors, diagnosis and disease management in fish while casting light on the potential associated public health hazards.

Abstract Mycobacterium fortuitum mycobacteremia and arthritis were diagnosed in a Briard dog from northern California. The dog was evaluated for lameness and had a history of immunosuppressive treatment and splenectomy for refractory immune thrombocytopenia. Cytological examination of synovial fluid from the right tarsus indicated marked suppurative inflammation with intralesional acid-fast bacteria. Mycobacterium fortuitum was cultured from joint fluid and blood; identification was based on PCR sequencing. Diagnosis was complicated by initial misidentification of the organism as an Actinomyces species. The dog was successfully treated with clarithromycin and enrofloxacin. The dog was later treated for a Grade III mast cell tumor of the thoracic limb with radiation therapy and chemotherapy and then died 2 years after the diagnosis of mycobacteremia because of extradural hemangiosarcoma of the spine.

Background Mycobacteriosis caused by non-tuberculous mycobacteria (NTM), is among the most chronic diseases of aquatic animals. In addition, fish mycobacteriosis has substantial economic consequences especially in the aquaculture and fisheries industry as infections may significantly decrease production and trade. Some fish NTM pathogens are highly virulent and zoonotic; as such, infection of aquaria with these pathogens is a public health concern. In this study, we report isolation of nine different NTM species from sixteen aquatic animals including different fish species, frogs and a crocodile. Given the clinical significance of Mycobacterium marinum and its close relation to Mycobacterium tuberculosis, as well as the significance of ESAT 6 and CFP-10 secretion in mycobacterial virulence, we analysed the esxA and esxB nucleotide sequences of M. marinum isolates identified in this study as well as other mycobacteria in the public databases. Results Mycobacterium shimoidei, Mycobacterium marinum, Mycobacterium chelonae, Mycobacterium septicum /M. peregrinum and Mycobacterium porcinum were isolated from gold fish, Guppy, exotic fish species in South Africa, koi and undefined fish, Knysna seahorse, as well Natal ghost frogs respectively, presenting tuberculosis like granuloma. Other NTM species were isolated from the studied aquatic animals without any visible lesions, and these include Mycobacterium sp. N845 T, Mycobacterium fortuitum , a member of the Mycobacterium avium complex, and Mycobacterium szulgai . Phylogenetic analysis of mycobacteria, based on esxA and esxB genes, separated slow growing from rapidly growing mycobacteria as well as pathogenic from non-pathogenic mycobacteria in some cases. Conclusions Isolation of the different NTM species from samples presenting granuloma suggests the significance of these NTM species in causing mycobacteriosis in these aquatic animals. The study also revealed the potential of esxA and esxB sequences as markers for phylogenetic classification of mycobacteria. Observations regarding use of esxA and esxB sequences for prediction of potential pathogenicity of mycobacteria warrants further investigation of these two genes in a study employing NTM species with well-defined pathogenicity.

Mycobacterial diseases, including tuberculosis (TB), remain the major health and economic challenges in livestock, underscoring the need to characterise the innate immune mechanisms involved in early bacterial containment. Alveolar macrophages (AMs) are the first line of defence against inhaled mycobacteria, yet the functional links between activation, polarisation, and phagocytic capacity in caprine AMs remain poorly defined. In this study, we compared a pH-dependent live-cell fluorescence assay with a culture-based method to evaluate phagocytosis and clearance of Mycobacterium fortuitum under different immunostimulatory conditions. AMs were stimulated in vitro with LPS or heat-inactivated Mycobacterium bovis (HIMB), and phagocytosis was assessed alongside activation and pro-inflammatory markers. Both approaches showed that LPS stimulation significantly enhanced mycobacterial clearance, despite reduced initial bacterial uptake. Moreover, this improved phagocytic capacity was associated with increased expression of the inducible Nitric Oxide Synthase (iNOS), MHCII, CD80, and CD86, as well as an elevated production of some pro-inflammatory cytokines. In contrast, HIMB induced cytokine secretion but failed to enhance activation markers or bacterial clearance. Collectively, these results establish the first association between pro-inflammatory activation and functional mycobacterial phagocytosis in caprine AMs and validate a robust methodological framework for studying innate immune responses relevant to TB and vaccine development in goats.

Adaptive immunity in homeotherms depends greatly on CD4+ Th cells which release cytokines in response to specific antigen stimulation. Whilst bony fish and poikilothermic tetrapods possess cells that express TcR and CD4-related genes (that exist in two forms in teleost fish; termed CD4-1 and CD4-2), to date there is no unequivocal demonstration that cells equivalent to Th exist. Thus, in this study we determined whether CD4-1+ lymphocytes can express cytokines typical of Th cells following antigen specific stimulation, using the zebrafish (Danio rerio). Initially, we analyzed the CD4 locus in zebrafish and found three CD4 homologues, a CD4-1 molecule and two CD4-2 molecules. The zfCD4-1 and zfCD4-2 transcripts were detected in immune organs and were most highly expressed in lymphocytes. A polyclonal antibody to zfCD4-1 was developed and used with an antibody to ZAP70 and revealed double positive cells by immunohistochemistry, and in the Mycobacterium marinum disease model CD4-1+ cells were apparent surrounding the granulomas typical of the infection. Next a prime-boost experiment, using human gamma globulin as antigen, was performed and revealed for the first time in fish that zfCD4-1+ lymphocytes increase the expression of cytokines and master transcription factors relevant to Th1/Th2-type responses as a consequence of boosting with specific antigen.

Background The function of Toll-like receptor 2 (TLR2) in host defense against pathogens, especially Mycobacterium tuberculosis (Mtb) is poorly understood. To investigate the role of TLR2 during mycobacterial infection, we analyzed the response of tlr2 zebrafish mutant larvae to infection with Mycobacterium marinum (Mm), a close relative to Mtb, as a model for tuberculosis. We measured infection phenotypes and transcriptome responses using RNA deep sequencing in mutant and control larvae. Results tlr2 mutant embryos at 2 dpf do not show differences in numbers of macrophages and neutrophils compared to control embryos. However, we found substantial changes in gene expression in these mutants, particularly in metabolic pathways, when compared with the heterozygote tlr2 +/− control. At 4 days after Mm infection, the total bacterial burden and the presence of extracellular bacteria were higher in tlr2 −/− larvae than in tlr2 +/− , or tlr2 +/+ larvae, whereas granuloma numbers were reduced, showing a function of Tlr2 in zebrafish host defense. RNAseq analysis of infected tlr2 −/− versus tlr2 +/− shows that the number of up-regulated and down-regulated genes in response to infection was greatly diminished in tlr2 mutants by at least 2 fold and 10 fold, respectively. Analysis of the transcriptome data and qPCR validation shows that Mm infection of tlr2 mutants leads to decreased mRNA levels of genes involved in inflammation and immune responses, including il1b , tnfb , cxcl11aa/ac , fosl1a , and cebpb . Furthermore, RNAseq analyses revealed that the expression of genes for Maf family transcription factors, vitamin D receptors, and Dicps proteins is altered in tlr2 mutants with or without infection. In addition, the data indicate a function of Tlr2 in the control of induction of cytokines and chemokines, such as the CXCR3-CXCL11 signaling axis. Conclusion The transcriptome and infection burden analyses show a function of Tlr2 as a protective factor against mycobacteria. Transcriptome analysis revealed tlr2 -specific pathways involved in Mm infection, which are related to responses to Mtb infection in human macrophages. Considering its dominant function in control of transcriptional processes that govern defense responses and metabolism, the TLR2 protein can be expected to be also of importance for other infectious diseases and interactions with the microbiome.

Non-tuberculous mycobacteria (NTM) are not only emerging and opportunistic pathogens of both humans and animals, but from a veterinary point of view some species induce cross-reactive immune responses that hamper the diagnosis of bovine tuberculosis (bTB) in both livestock and wildlife. Little information is available about NTM species circulating in wildlife species of South Africa. In this study, we determined the diversity of NTM isolated from wildlife species from South Africa as well as Botswana. Thirty known NTM species and subspecies, as well as unidentified NTM, and NTM closely related to were identified from 102 isolates cultured between the years 1998 and 2010, using a combination of molecular assays viz PCR and sequencing of different Mycobacterial house-keeping genes as well as single nucleotide polymorphism (SNP) analysis. The NTM identified in this study include the following species which were isolated from tissue with tuberculosis- like lesions in the absence of complex (MTBC) implying their potential role as pathogens of animals: subsp. species closely related to JMD 601, subsp. sp. GR-2007, , and / sp. GR-2007, and a potential novel species closely related to were found for the first time in this study to be potential pathogens of animals. was isolated from a sample originating from a tuberculin skin test positive reactor, demonstrating its potential to elicit inappropriate immune responses in animals that may interfere with diagnosis of tuberculosis by immunology. subsp. was the most frequently detected NTM identified in 37 of the 102 isolates. Other NTM species were also isolated from animals not showing any pathological changes. Knowledge gained in this study contribute to the understanding of NTM species circulating in wild animals in South Africa and the pathogenic potential of certain species, whose role in disease causation need to be examined, as well as to a certain extent the potential of to hamper the diagnosis of bTB.

Fish mycobacteriosis, a chronic progressive disease caused by nontuberculous mycobacteria (NTM), affects marine, brackish, and freshwater fish. Mycobacterium marinum (M. marinum), the most important of the NTM, infects fresh and marine water fish causing necrotizing granulomas and associated morbidity and mortality. M. marinum causes disease in zebrafish in a dose-dependent fashion. The M. marinum-induced disease in the zebrafish is associated with the development of necrotizing granulomas with abundant bacteria in the necrotic areas. Acute infection with high infectious doses of M. marinum infection in zebrafish was characterized by uncontrolled replication of the pathogen and death of all fish within 16 days, while chronic infections were marked by the formation of granulomas in different organs and longer survival in the range of 4–8 weeks. This review therefore synthesizes recent advances in our understanding of M. marinum’s infection of zebrafish, molecular pathogenesis, virulence mechanisms, and immune evasion strategies in zebrafish, while also highlighting the host immune effector responses and the virulence mechanisms of M. marinum.

Emerald tree boas ( Corallus batesii ) are boids that in situ occurs in forested habitats in the Amazon Basin. The mycobacterial species can infect reptiles but the species Mycolicibacterium fortuitum was identified only in feces samples of ex situ Python regius and was isolated from granulomatous lesions of an ex situ Iguana iguana when was still part of the genus Mycobacterium . This article aims to report a mycobacteria infection case in a female Corallus batesii kept under human care. The animal presented apathy and 2 months of anorexia, being found dead. The necropsy revealed presence of tracheal and pulmonary nodules besides multifocal, bacterial, granulomatous pneumonia. After Fite-Faraco histochemical staining, immunohistochemistry, semi-nested polymerase chain reaction (PCR) and genetic sequencing the Mycolicibacterium fortuitum complex was diagnosed with 99.54% of nucleotide similarity. This mycobacterial species was already pointed out as an important nosocomial pathogen and more studies are necessary to explore their zoonotic potential.

In current literature, data assessing the acid-base equilibrium in animals and humans during bacterial infection are rare. This study aimed to evaluate acid-base deteriorations in growing goats with experimentally induced NTM (nontuberculous mycobacteria) infections by application of the traditional Henderson-Hasselbalch approach and the strong ion model. NTM-challenged animals were orally inoculated with either Mycobacterium avium subsp. hominissuis (MAH; n = 18) or Mycobacterium avium subsp. paratuberculosis (MAP; n = 48). Twenty-five goats served as non-infected controls. Until 51 st week post-inoculation (wpi), blood gas analysis, serum biochemical analysis, and serum electrophoresis were performed on venous blood. Fifty percent (9/18) of goats inoculated with MAH developed acute clinical signs like apathy, fever, and diarrhea. Those animals died or had to be euthanized within 11 weeks post-inoculation. This acute form of NTM-infection was characterized by significantly lower concentrations of sodium, calcium, albumin, and total protein, as well as significantly higher concentrations of gamma globulin, associated with reduced albumin/globulin ratio. Acid-base status indicated alkalosis, but normal base excess and HCO 3 - concentrations, besides significantly reduced levels of SID (strong ion difference), A tot Alb (total plasma concentration of weak non-volatile acids, based on albumin), A tot TP (A tot based on total protein) and markedly lower SIG (strong ion gap). The remaining fifty percent (9/18) of MAH-infected goats and all goats challenged with MAP survived and presented a more sub-clinical, chronic form of infection mainly characterized by changes in serum protein profiles. With the progression of the disease, concentrations of gamma globulin, and total protein increased while albumin remained lower compared to controls. Consequently, significantly reduced albumin/globulin ratio and lower A tot Alb as well as higher A tot TP were observed. Changes were fully compensated with no effect on blood pH. Only the strong ion variables differentiated alterations in acid-base equilibrium during acute and chronic NTM-infection.