Human MCTS1-dependent translation of JAK2 is essential for IFN-γ immunity to mycobacteria.

Human inherited disorders of interferon-gamma (IFN-γ) immunity underlie severe mycobacterial diseases. We report X-linked recessive MCTS1 deficiency in men with mycobacterial disease from kindreds of different ancestries (from China, Finland, Iran, and Saudi Arabia). Complete deficiency of this translation re-initiation factor impairs the translation of a subset of proteins, including the kinase JAK2 in all cell types tested, including T lymphocytes and phagocytes. JAK2 expression is sufficiently low to impair cellular responses to interleukin-23 (IL-23) and partially IL-12, but not other JAK2-dependent cytokines. Defective responses to IL-23 preferentially impair the production of IFN-γ by innate-like adaptive mucosal-associated invariant T cells (MAIT) and γδ T lymphocytes upon mycobacterial challenge. Surprisingly, the lack of MCTS1-dependent translation re-initiation and ribosome recycling seems to be otherwise physiologically redundant in these patients. These findings suggest that X-linked recessive human MCTS1 deficiency underlies isolated mycobacterial disease by impairing JAK2 translation in innate-like adaptive T lymphocytes, thereby impairing the IL-23-dependent induction of IFN-γ.

T Cell Interactions in Mycobacterial Granulomas: Non-Specific T Cells Regulate Mycobacteria-Specific T Cells in Granulomatous Lesions.

Infections with pathogenic mycobacteria are controlled by the formation of a unique structure known as a granuloma. The granuloma represents a host-pathogen interface where bacteria are killed and confined by the host response, but also where bacteria persist. Previous work has demonstrated that the T cell repertoire is heterogenous even at the single granuloma level. However, further work using pigeon cytochrome C (PCC) epitope-tagged BCG (PCC-BCG) and PCC-specific 5CC7 RAG-/- TCR transgenic (Tg) mice has demonstrated that a monoclonal T cell population is able to control infection. At the chronic stage of infection, granuloma-infiltrating T cells remain highly activated in wild-type mice, while T cells in the monoclonal T cell mice are anergic. We hypothesized that addition of an acutely activated non-specific T cell to the monoclonal T cell system could recapitulate the wild-type phenotype. Here we report that activated non-specific T cells have access to the granuloma and deliver a set of cytokines and chemokines to the lesions. Strikingly, non-specific T cells rescue BCG-specific T cells from anergy and enhance the function of BCG-specific T cells in the granuloma in the chronic phase of infection when bacterial antigen load is low. In addition, we find that these same non-specific T cells have an inhibitory effect on systemic BCG-specific T cells. Taken together, these data suggest that T cells non-specific for granuloma-inducing agents can alter the function of granuloma-specific T cells and have important roles in mycobacterial immunity and other granulomatous disorders.

Mycobacterium chimaera as an Underestimated Cause of NTM Lung Diseases in Patients Hospitalized in Pulmonary Wards.

Mycobacterium chimaera is the newly described species belonging to Mycobacterium avium complex (MAC), with morphology and growth characteristics closely related to Mycobacterium intracellulare. The aim of this retrospective study was to analyze the frequency and clinical significance of M. chimaera identification in the population of patients with previous positive respiratory cultures for M. intracellulare or MAC. 200 strains of M. intracellulare or MAC, isolated from respiratory specimens of patients hospitalized in pulmonary wards, between 2011 and 2020, were retrospectively analyzed with GenoType NTM-DR test. 88 (44%) of strains were re-classified to M. chimaera species. Analysis of clinical data in 30 patients with positive M. chimaera isolates revealed that they were diagnosed with chronic obstructive pulmonary disease (COPD) - 27%, past tuberculosis - 20%, or interstitial lung diseases - 17%, respectively. Non-tuberculous mycobacterial lung disease (NTMLD) caused by M. chimaera has been recognized in 53% of patients, most often in those presenting with post-tuberculous lung lesions. M. chimaera was almost exclusively isolated from respiratory specimens of patients with underlying lung diseases, especially those with COPD and/or past tuberculosis. NTMLD due to M. chimaera was diagnosed predominantly in patients with past tuberculosis.

Dual Nature of Relationship between Mycobacteria and Cancer.

Although the therapeutic effect of mycobacteria as antitumor agents has been known for decades, recent epidemiological and experimental studies have revealed that mycobacterium-related chronic inflammation may be a possible mechanism of cancer pathogenesis. Mycobacterium tuberculosis and non-tuberculous Mycobacterium avium complex infections have been implicated as potentially contributing to the etiology of lung cancer, whereas Mycobacterium ulcerans has been correlated with skin carcinogenesis. The risk of tumor development with chronic mycobacterial infections is thought to be a result of many host effector mechanisms acting at different stages of oncogenesis. In this paper, we focus on the nature of the relationship between mycobacteria and cancer, describing the clinical significance of mycobacteria-based cancer therapy as well as epidemiological evidence on the contribution of chronic mycobacterial infections to the increased lung cancer risk.

Monocyte progenitors give rise to multinucleated giant cells.

The immune response to mycobacteria is characterized by granuloma formation, which features multinucleated giant cells as a unique macrophage type. We previously found that multinucleated giant cells result from Toll-like receptor-induced DNA damage and cell autonomous cell cycle modifications. However, the giant cell progenitor identity remained unclear. Here, we show that the giant cell-forming potential is a particular trait of monocyte progenitors. Common monocyte progenitors potently produce cytokines in response to mycobacteria and their immune-active molecules. In addition, common monocyte progenitors accumulate cholesterol and lipids, which are prerequisites for giant cell transformation. Inducible monocyte progenitors are so far undescribed circulating common monocyte progenitor descendants with high giant cell-forming potential. Monocyte progenitors are induced in mycobacterial infections and localize to granulomas. Accordingly, they exhibit important immunological functions in mycobacterial infections. Moreover, their signature trait of high cholesterol metabolism may be piggy-backed by mycobacteria to create a permissive niche.

Ten cases of Mycobacterium avium subsp. hominissuis infections linked to equine abortions in Japan, 2018-2019.

Bacterial placentitis in horses commonly results in abortion, premature birth or compromised neonatal foal health. Although mycobacterial infections are generally uncommon in horses, 10 equine abortion cases caused by Mycobacterium avium subsp. hominissuis (MAH) infections occurred between 2018 and 2019 in Japan. They occurred on seven Thoroughbred horse farms in the Hidaka district of Hokkaido, but direct contact among the mares on different farms was not recorded. Most cases were characterized by extensive pathological lesions of the placenta, which are not typical in cases of common pathogenic bacteria such as Streptococcus zooepidemicus and Escherichia coli. All abortions featured white-yellow exudates on the surface of the placenta. Mycobacterial granuloma formations were histologically found in the placenta and fetal organs, and acid-fast bacteria were isolated from the placenta, fetal samples (heart, lung, liver, kidney, spleen and stomach contents) or uterine lavage fluid. The greatest number of bacteria was isolated from necrotic lesions on the placenta, which could be an important site for bacterial isolation in mycobacterial equine abortions. The isolates were identified as MAH based on internal genome sequences. In variable number tandem repeat analysis, all patterns of the strains were identical. Single nucleotide polymorphism analysis of the core genome grouped all strains in the II-a/SC3 subcluster. Both results reveal that these strains share the same genetic background, suggesting that the horses had been infected by the same unknown contagious source.

Soybean lectin induces autophagy through P2RX7 dependent activation of NF-κB-ROS pathway to kill intracellular mycobacteria.

BACKGROUND: Host-directed therapy is considered a novel anti-tuberculosis strategy in tackling the tuberculosis burden through autophagy induction by various inducers to curtail the growth of intracellular Mycobacterium tuberculosis. METHODS: In this study, we investigated the anti-tubercular role of soybean lectin, a lectin isolated from Glycine max (Soybean). Effect of SBL on intracellular mycobacterial viability through autophagy and the mechanism involved in differentiated THP-1 cells was studied using different experimental approaches. RESULTS: We initially performed a time kinetic experiment with the non-cytotoxic dose of SBL (20 µg/ml) and observed autophagy induction after 24 h of treatment. Abrogation of autophagy in the presence of 3-MA and an increase in LC3 puncta formation upon Baf-A1 addition elucidated the specific effect on autophagy and autophagic flux. SBL treatment also led to autophagy induction in mycobacteria infected macrophages that restricted the intracellular mycobacterial growth, thus emphasizing the host defensive role of SBL induced autophagy. Mechanistic studies revealed an increase in P2RX7 expression, NF-κB activation and reactive oxygen species generation upon SBL treatment. Inhibition of P2RX7 expression suppressed NF-κB dependent ROS level in SBL treated cells. Moreover, SBL induced autophagy was abrogated in the presence of either different inhibitors or P2RX7 siRNA, leading to the reduced killing of intracellular mycobacteria. CONCLUSION: Taken together, these results conclude that SBL induced autophagy exerts an anti-mycobacterial effect in P2RX7-NF-κB dependent manner through the generation of ROS. GENERAL SIGNIFICANCE: This study has provided a novel anti-mycobacterial role of SBL, which may play an important role in devising new therapeutic interventions.

Occurrence of Mycobacterium spp. in ornamental fish.

INTRODUCTION AND OBJECTIVE: Fish mycobacteriosis is a chronic granulomatous disease caused by several species of bacteria from the genus Mycobacterium, described as nontuberculous mycobacteria (NTM). The most important species causing fish mycobacterioses are M. chelonae, M. fortuitum, and M. marinum. Mycobacteria infecting fish also include zoonotic pathogens. M. marinum is the cause of most cases of fish-related mycobacterial infection in humans. The disease occurs more frequently in workers in the fishing industry, people whose hobbies involve water activities, and aquarists. The aim of the present study was to examine the occurrence of different species of mycobacteria in freshwater ornamental fish. MATERIAL AND METHODS: The occurrence of Mycobacterium spp. in freshwater ornamental fish was studied from January 2015 - December 2016. Material isolated from skin scrapings, contents of the digestive tracts, and internal organs of ornamental fish was stained with Ziehl-Neelsen (ZN) and inoculated on Lowenstein-Jensen medium. All isolates found positive by ZN were identified by amplification of the gene encoding the Hsp65 protein. A total of 408 samples obtained from 136 ornamental fish from 36 species were tested. RESULTS: Using the culture method Mycobacterium was isolated from 69 fish (50.1%) and 99 samples (24.3%). Sequence analysis of gene fragments coding for the Hsp65 protein of 99 isolates revealed occurrence of 13 species of mycobacteria: M. abscessus, M. chelonae, M. fortuitum, M. gordonae, M. marinum, M. mucogenicum, M. neoaurum, M. peregrinum, M. salmoniphilum, M. saopaulense, M. senegalense, M. septicum, and M. szulgai. CONCLUSIONS: The obtained results indicate a significant role of ornamental fish as a source of mycobacteria which are potentially dangerous,especially to humans.

Combination of Mycobacterium indicus pranii and Heat-Induced Promastigotes Cures Drug-Resistant Leishmania Infection: Critical Role of Interleukin-6-Producing Classical Dendritic Cells.

The major issues in available therapeutic modalities against leishmaniasis are cost, toxicity, and the emergence of drug resistance. The aim of this work was to develop a successful therapeutic adjuvant against drug-resistant Leishmania donovani infection by means of combining Mycobacterium indicus pranii with heat-induced promastigotes (HIP). One-month postinfected BALB/c mice were administered subcutaneously with M. indicus pranii (108 cells) and HIP (100 µg) for 5 days. Spleens were harvested for flow cytometric and reverse transcriptase PCR analysis. The antileishmanial effect of the combination strategy was associated with induction of a disease-resolving Th1 and Th17 response with simultaneous downregulation of CD4+ CD25+ Foxp3+ (nTreg) cells and CD4+ CD25- Foxp3- (Tr1) cells in the spleen. The significant expansion of CD4+ TCM (CD4+ CD44hi CD11ahi CD62Lhi) cells was a further interesting outcome of this therapeutic strategy in the context of long-term protection of hosts against secondary infection. Toll-like receptor 2 (TLR2) was also found instrumental in this antiparasitic therapy. Induced interleukin-6 (IL-6) production from expanded CD11c+ CD8α+ (cDC1) and CD11c+ CD11b+ (cDC2) dendritic cells (DCs) but not from the CD11b+ Ly6c+ inflammatory monocytes (iMOs), was found critical in the protective expansion of Th17 as evidenced by an in vivo IL-6 neutralization assay. It also promoted the hematopoietic conversion toward DC progenitors (pre-DCs) from common dendritic cell progenitors (CDPs), the immediate precursors, in bone marrow. This novel combinational strategy demonstrated that expansion of Th17 by IL-6 released from CD11c+ classical DCs is crucial, together with the conventional Th1 response, to control drug-resistant infection.

Genetic, Immunological, and Clinical Features of the First Mexican Cohort of Patients with Chronic Granulomatous Disease.

PURPOSE: Chronic granulomatous disease (CGD) is a primary immunodeficiency characterized by an inability of phagocytes to produce reactive oxygen species, impairing their killing of various bacteria and fungi. We summarize here the 93 cases of CGD diagnosed in Mexico from 2011 to 2019. METHODS: Thirteen Mexican hospitals participated in this study. We describe the genetic, immunological, and clinical features of the 93 CGD patients from 78 unrelated kindreds. RESULTS: Eighty-two of the patients (88%) were male. All patients developed bacterial infections and 30% suffered from some kind of fungal infection. Fifty-four BCG-vaccinated patients (58%) presented infectious complications of BCG vaccine. Tuberculosis occurred in 29%. Granulomas were found in 56% of the patients. Autoimmune and inflammatory diseases were present in 15% of patients. A biological diagnosis of CGD was made in 89/93 patients, on the basis of NBT assay (n = 6), DHR (n = 27), and NBT plus DHR (n = 56). The deficiency was complete in all patients. The median age of biological diagnosis was 17 months (range, 0-186 months). A genetic diagnosis was made in 83/93 patients (when material was available), corresponding to CYBB (n = 64), NCF1 (n = 7), NCF2 (n = 7), and CYBA (n = 5) mutations. CONCLUSIONS: The clinical manifestations in these Mexican CGD patients were similar to those in patients elsewhere. This cohort is the largest in Latin America. Mycobacterial infections are an important cause of morbidity in Mexico, as in other countries in which tuberculosis is endemic and infants are vaccinated with BCG. X-linked CGD accounted for most of the cases in Mexico, as in other Latin American countries. However, a significant number of CYBA and NCF2 mutations were identified, expanding the spectrum of known causal mutations.

Preliminary evaluation of the positively and negatively charge effects of tetra-substituted porphyrins on photoinactivation of rapidly growing mycobacteria.

This manuscript reports, at the first time, the photoinactivation evaluation of tetra-cationic and anionic porphyrins as photosensitizers (PS) for the photodynamic inactivation (PDI) of rapidly growing mycobacteria strains. Two different charged porphyrin groups were obtained commercially. PDI experiments in the strains Mycobacterium massiliense e Mycobacterium fortuitum conducted with adequate concentration (without aggregation) of photosensitizer under white light at a fluence rate of 50 mW/cm2 over 90 min showed that the most effective PS caused a 100 times reduction in the concentration of viable mycobacteria. The present results show that porphyrin with positively charge are more efficient PS than anionic porphyrin (negatively charged) against M. massiliense e M. fortuitum. It is also clear that the effectiveness of the molecule as PS for PDI studies with mycobacteria is strongly related with the porphyrin peripheral charge, and consequently their solubility in physiological media. Cationic PSs might be promising anti-mycobacteria PDI agents with potential applications in medical clinical cases and bioremediation.

Cutaneous Mycobacterial Infections.

Humans encounter mycobacterial species due to their ubiquity in different environmental niches. In many individuals, pathogenic mycobacterial species may breach our first-line barrier defenses of the innate immune system and modulate the activation of phagocytes to cause disease of the respiratory tract or the skin and soft tissues, sometimes resulting in disseminated infection. Cutaneous mycobacterial infections may cause a wide range of clinical manifestations, which are divided into four main disease categories: (i) cutaneous manifestations of Mycobacterium tuberculosis infection, (ii) Buruli ulcer caused by Mycobacterium ulcerans and other related slowly growing mycobacteria, (iii) leprosy caused by Mycobacterium leprae and Mycobacterium lepromatosis, and (iv) cutaneous infections caused by rapidly growing mycobacteria. Clinically, cutaneous mycobacterial infections present with widely different clinical presentations, including cellulitis, nonhealing ulcers, subacute or chronic nodular lesions, abscesses, superficial lymphadenitis, verrucous lesions, and other types of findings. Mycobacterial infections of the skin and subcutaneous tissue are associated with important stigma, deformity, and disability. Geography-based environmental exposures influence the epidemiology of cutaneous mycobacterial infections. Cutaneous tuberculosis exhibits different clinical phenotypes acquired through different routes, including via extrinsic inoculation of the tuberculous bacilli and dissemination to the skin from other sites, or represents hypersensitivity reactions to M. tuberculosis infection. In many settings, leprosy remains an important cause of neurological impairment, deformity, limb loss, and stigma. Mycobacterium lepromatosis, a mycobacterial species related to M. leprae, is linked to diffuse lepromatous leprosy of Lucio and Latapí. Mycobacterium ulcerans produces a mycolactone toxin that leads to subcutaneous tissue destruction and immunosuppression, resulting in deep ulcerations that often produce substantial disfigurement and disability. Mycobacterium marinum, a close relative of M. ulcerans, is an important cause of cutaneous sporotrichoid nodular lymphangitic lesions. Among patients with advanced immunosuppression, Mycobacterium kansasii, the Mycobacterium avium-intracellulare complex, and Mycobacterium haemophilum may cause cutaneous or disseminated disease. Rapidly growing mycobacteria, including the Mycobacterium abscessus group, Mycobacterium chelonei, and Mycobacterium fortuitum, are increasingly recognized pathogens in cutaneous infections associated particularly with plastic surgery and cosmetic procedures. Skin biopsies of cutaneous lesions to identify acid-fast staining bacilli and cultures represent the cornerstone of diagnosis. Additionally, histopathological evaluation of skin biopsy specimens may be useful in identifying leprosy, Buruli ulcer, and cutaneous tuberculosis. Molecular assays are useful in some cases. The treatment for cutaneous mycobacterial infections depends on the specific pathogen and therefore requires a careful consideration of antimicrobial choices based on official treatment guidelines.

Clinical and molecular features of X-linked hyper IgM syndrome - An experience from North India.

X-linked hyper IgM Syndrome (XLHIGM), the most frequent form of the Hyper IgM syndromes is a primary immune deficiency resulting from a mutation in the CD40 ligand gene (CD40LG). We analyzed the clinical and laboratory features of ten patients with XLHIGM, who were diagnosed at a tertiary care hospital in North India. Most common infections were sinopulmonary infections (80%) and diarrhea (50%). Sclerosing cholangitis and necrotising fasciitis were noted in one patient each. Three novel mutations in CD40LG (c.429_429 delA, p. G144DfsX5; c.500 G > A, p.G167E and c.156 G > C, p.K52 N) were detected. In addition, we found one missense mutation, two splice site mutations and two large deletions, which have been previously reported. Four (4) patients had expired at the time of analysis. We report the first series of XLHIGM from North India where we have documented unique features such as pulmonary alveolar proteinosis and infections with Mycobacterium sp.

Ready Experimental Translocation of Mycobacterium canettii Yields Pulmonary Tuberculosis.

Mycobacterium canettii, which has a smooth colony morphology, is the tuberculous organism retaining the most genetic traits from the putative last common ancestor of the rough-morphology Mycobacterium tuberculosis complex. To explore whether M. canettii can infect individuals by the oral route, mice were fed phosphate-buffered saline or 106M. canettii mycobacteria and sacrificed over a 28-day experiment. While no M. canettii was detected in negative controls, M. canettii-infected mice yielded granuloma-like lesions for 4/4 lungs at days 14 and 28 postinoculation (p.i.) and positive PCR detection of M. canettii for 5/8 mesenteric lymph nodes at days 1 and 3 p.i. and 5/6 pooled stools collected from day 1 to day 28 p.i. Smooth M. canettii colonies grew from 68% of lungs and 36% of spleens and cervical lymph nodes but fewer than 20% of axillary lymph nodes, livers, brown fat samples, kidneys, or blood samples throughout the 28-day experiment. Ready translocation in mice after digestive tract challenge demonstrates the potential of ingested M. canettii organisms to relocate to distant organs and lungs. The demonstration of this relocation supports the possibility that populations may be infected by environmental M. canettii.

Guanine nucleotide exchange factor -H1 promotes inflammatory cytokine production and intracellular mycobacterial elimination in macrophages.

Mycobacterium tuberculosis (M.tb), which causes tuberculosis, is a host-adapted intracellular pathogen that can live within macrophages owning to its ability to arrest phagolysosome biogenesis. The guanine nucleotide exchange factor H1 (GEF-H1) may contribute to the phagocytosis of bacteria by macrophages through mediating the crosstalk between microtubules and the actin cytoskeleton. Its role in Shigella infection has been determined but little is known about the role of GEF-H1 in mycobacterial infection. In the present study, we demonstrated that GEF-H1 functioned as a key regulator of the macrophage-mediated anti-mycobacterial response. We found that both mRNA and protein expression levels of GEF-H1 were significantly upregulated in macrophage during mycobacterial infection. Moreover, silencing of GEF-H1 with specific siRNAs reduced the phosphorylation of p38 mitogen-activated protein kinase and TANK binding kinase 1 as well as the expression of interleukin-1ß (IL-1ß), IL-6, and interferon-ß (IFN-ß), without affecting nitric oxide production or autophagy. Importantly, GEF-H1 depletion attenuated macrophages-mediated mycobacterial phagocytosis and elimination. Taken together, our data supported that GEF-H1 was a novel regulator of inflammatory cytokine production and mycobacterial elimination, and may serve as a novel potential target for clinical treatment of tuberculosis.

Mycobacterium iranicum bacteremia and hemophagocytic lymphohistiocytosis: a case report.

BACKGROUND: Mycobacterium iranicum has recently been recognised as an opportunistic human pathogen. Although infectious conditions represent frequent triggers for hemophagocytic lymphohistiocytosis, non-tuberculous mycobacterial infections are rarely associated with this entity. To this date, M. iranicum infection has never been reported in France, has never been associated with hemophagocytic lymphohistiocytosis and has never been found to be multi-resistant on standardized antimicrobial susceptibility testing. CASE PRESENTATION: We report a case of a French Caucasian man with secondary hemophagocytic lymphohistiocytosis in the context of M. iranicum bacteraemia and Hodgkin's disease. We review available data concerning M. iranicum antimycobacterial susceptibility testing and treatment outcomes. We also review the association between hemophagocytic lymphohistiocytosis and non-tuberculous mycobacterial infections. CONCLUSION: Interpretation of M. iranicum positive cultures remains a clinical challenge and non-tuberculous mycobacterial infections need to be considered in secondary hemophagocytic lymphohistiocytosis differential diagnosis.

Microbiological problems and biofilms associated with Mycobacterium chimaera in heater-cooler units used for cardiopulmonary bypass.

The role of heater-cooler units (HCUs) in the transmission of Mycobacterium chimaera during open heart surgery has been recognized since 2013. Subsequent investigations uncovered a remarkable global outbreak reflecting the wide distribution of implicated devices. HCUs are an essential component of cardiopulmonary bypass operations and their withdrawal would severely affect capacity for life-saving cardiac surgery. However, studies have demonstrated that many HCUs are contaminated with a wide range of micro-organisms, including M. chimaera and complex biofilms. Whole genome sequencing of M. chimaera isolates recovered from one manufacturer's HCUs, worldwide, has demonstrated a high level of genetic similarity, for which the most plausible hypothesis is a point source contamination of the devices. Dissemination of bioaerosols through breaches in the HCU water tanks is the most likely route of transmission and airborne bacteria have been shown to have reached the surgical field even with the use of ultraclean theatre ventilation. Controlling the microbiological quality of the water circulating in HCUs and reducing biofilm formation has been a major challenge for many hospitals. However, enhanced decontamination strategies have been recommended by manufacturers, and, although they are not always effective in eradicating M. chimaera from HCUs, UK hospitals have not reported any new cases of M. chimaera infection since implementing these mitigation strategies. Water safety groups in hospitals should be aware that water in medical devices such as HCUs may act as a vector in the transmission of potentially fatal water-borne infections.

Feline leprosy due to Candidatus 'Mycobacterium tarwinense':Further clinical and molecular characterisation of 15 previously reported cases and an additional 27 cases

OBJECTIVES: This paper, the first in a series of three on 'feline leprosy', provides a detailed description of disease referable to Candidatus 'Mycobacterium tarwinense', the most common cause of feline leprosy in Victoria, Australia. METHODS: Cases were sourced retrospectively and prospectively for this observational study, describing clinical, geographical and molecular microbiological data for cats definitively diagnosed with Candidatus 'M tarwinense' infection. RESULTS: A total of 145 cases of feline leprosy were scrutinised; 114 'new' cases were sourced from the Victorian Infectious Diseases Reference Laboratory records, veterinary pathology laboratories or veterinarians, and 31 cases were derived from six published studies. Forty-two cats were definitively diagnosed with Candidatus 'M tarwinense' infection. Typically, cats were between 3 and 11 years of age, with no gender predilection, and were generally systemically well. All had outdoor access. Most cats underwent surgical resection of lesions with adjunctive medical therapy, often utilising a combination of oral clarithromycin and rifampicin for at least 3 months. Prognosis for recovery was generally good. Resolution of lesions was not observed in the absence of treatment, but a number of untreated cats continued to enjoy an acceptable quality of life despite persistence of the disease, which extended locally but did not appear to disseminate to internal organs. Preliminary results of draft genome sequencing confirmed that the species is a member of the Mycobacterium simiae complex. CONCLUSIONS AND RELEVANCE: Candidatus 'M tarwinense', a fastidious member of the M simiae complex, is capable of causing feline leprosy with a tendency to produce lesions on the head, particularly involving the eyes and periocular skin. The disease has an indolent clinical course and generally responds favourably to therapy despite lesions often containing large numbers of organisms. Detailed genomic analysis may yield clues as to the environmental niche and culture requirement of this elusive organism. Prospective treatment trials and/or drug susceptibility testing in specialised systems would further inform treatment recommendations.

Efferocytosis and extrusion of leukocytes determine the progression of early mycobacterial pathogenesis.

Macrophages and neutrophils are the first responders to invading pathogens and contribute strongly to the host defense against intracellular pathogens. The collective interplay and dynamic interactions between these leukocytes are to a large extent not understood. In the present study, we have investigated their role using a combination of confocal laser-scanning and electron microscopy in a zebrafish model for tuberculosis, a local Mycobacterium marinum infection in the tissue of the larval tail fin. Our results show that neutrophils are efficient in phagocytosis of mycobacteria and that they contribute largely to their dissemination. Macrophages appear to play a major role in efferocytosis, phagocytosis of dead cells that contain bacterial content. Phagocytic cells with large bacterial aggregates are formed that can be extruded out of the tissue after cell death. Alternatively, these excessively infected cells can undergo necrosis leading to immediate recruitment of surrounding leukocytes and subsequent phagocytosis of released bacteria. Our data show that these necrotic burst events result in progression of the infection, whereas extrusion abates the infection.

Mycobacteria emulsified in olive oil-in-water trigger a robust immune response in bladder cancer treatment.

The hydrophobic composition of mycobacterial cell walls leads to the formation of clumps when attempting to resuspend mycobacteria in aqueous solutions. Such aggregation may interfere in the mycobacteria-host cells interaction and, consequently, influence their antitumor effect. To improve the immunotherapeutic activity of Mycobacterium brumae, we designed different emulsions and demonstrated their efficacy. The best formulation was initially selected based on homogeneity and stability. Both olive oil (OO)- and mineral oil-in-water emulsions better preserved the mycobacteria viability and provided higher disaggregation rates compared to the others. But, among both emulsions, the OO emulsion increased the mycobacteria capacity to induce cytokines' production in bladder tumor cell cultures. The OO-mycobacteria emulsion properties: less hydrophobic, lower pH, more neutralized zeta potential, and increased affinity to fibronectin than non-emulsified mycobacteria, indicated favorable conditions for reaching the bladder epithelium in vivo. Finally, intravesical OO-M. brumae-treated mice showed a significantly higher systemic immune response, together with a trend toward increased tumor-bearing mouse survival rates compared to the rest of the treated mice. The physicochemical characteristics and the induction of a robust immune response in vitro and in vivo highlight the potential of the OO emulsion as a good delivery vehicle for the mycobacterial treatment of bladder cancer.