Different Species Of Mycobacteria Research Articles

984. Detection of Mycobacterial Species from Specimens Submitted for Metagenomic Analysis

Abstract Background A national U.S. epidemic of non-tuberculous mycobacterial (NTM) infections is occurring at rates unseen over earlier decades, resulting in substantial numbers of pathogenic sequelae. Culture of mycobacteria is laborious, often requiring weeks for cultivation and speciation. Next generation sequencing (NGS) to detect NTM from clinical specimens has advantages over culture methods. From January 2018 to June 2022 we queried a large national NGS database to detect NTM rates and species. Methods DNA was isolated from 431,716 patient specimens collected from a variety of body sites: sputum, urine, sinus, wound or an unspecified swabs. Employing an Illumina’s 16S and ITS targeted-gene, deep sequencing approach, bacterial and/or fungal species resident in the specimen were determined. The identity and relative abundance of mycobacterial DNA recovered for each specimen were reported by species as the primary outcomes. Results Of the 431,716 specimens analyzed in this 4.5 year retrospective study, 0.001% (468) contained mycobacterial DNA. Forty different species of mycobacteria were detected with the most common frequency including: M abscessus, 40%; M mucogenicum, 13%; M. tuberculosis, 8.5% and M immunogenum 4.6%. M. avian and M. intracellulare were each detected in only 4% of the positive NTM specimens. 15% were other NTM species and 15% were not speciated NTM. Between 2018-2022 of the 468 NTM, the annual number of M. abscessus was 38, 53, 41 and 41, respectively. The concentration or relative abundance of mycobacterial DNA within each specimen varied from 4 to 100% of the total bacterial DNA recovered. Conclusion Over 4.5 years , NGS performed at a national molecular diagnostic laboratory detected 40 NTM species with a predominant fraction as M. abscessus (40%), supporting the clinical concern for an epidemic increase in M. abscessus infections during the last half decade. These data support the view that NGS metagenomics can uncover NTM epidemiological trends and implicate NTM infections. Disclosures Joseph F. John, Jr., MD, FACP, FIDSA, MicroGenDx: Advisor/Consultant Michael G. Schmidt, PhD, MicroGenDx: Advisor/Consultant Courtney L. Jarvis, PhD, MicroGenDX: Employee Niccole Diaz, BS, MicroGenDX: Advisor/Consultant Rick Martin, BS, MicroGenDX: Ownership Interest

Overexpression of a membrane transport system MSMEG_1381 and MSMEG_1382 confers multidrug resistance in Mycobacterium smegmatis

Mycobacterium tuberculosis is a leading cause of human mortality worldwide, and the emergence of drug-resistant strains demands the discovery of new classes of antimycobacterial that can be employed in the therapeutic pipeline. Previously, a secondary metabolite, chrysomycin A, isolated from Streptomyces sp. OA161 displayed potent bactericidal activity against drug-resistant clinical isolates of M. tuberculosis and different species of mycobacteria. The antibiotic inhibits mycobacterial topoisomerase I and DNA gyrase, leading to bacterial death, but the mechanisms that could cause resistance to this antibiotic are currently unknown. To further understand the resistance mechanism, using M. smegmatis as a model, spontaneous resistance mutants were isolated and subjected to whole-genome sequencing. Mutation in a TetR family transcriptional regulator MSMEG_1380 was identified in the resistant isolates wherein the gene was adjacent to an operon encoding membrane proteins MSMEG_1381 and MSMEG_1382. Sequence analysis and modeling studies indicated that MSMEG_1381 and MSMEG_1382 are components of the Mmp family of efflux pumps and over-expression of either the operon or individual genes conferred resistance to chrysomycin A, isoniazid, and ethambutol. Our study highlights the role of membrane transporter proteins in conferring multiple drug resistance and the utility of recombinant strains overexpressing membrane transporters in the drug screening pipeline.

Mycobacterial Cloacitis with Systemic Dissemination in a Hermann's Tortoise (Testudo hermanni)

Abstract In recent years, many nontuberculous mycobacteria (NTM) species have been recognized as pathogens for humans and animals. Molecular diagnostic techniques enable rapid identification and characterization of the different species of mycobacteria. NTM are inhabitants of the soil and water, and enter the body through a defect in the skin or mucosa, causing infections in immunocompromised subjects. Mycobacteriosis has been described in reptiles, especially in chelonians, but the incidence seems to be low in captivity. To date, mycobacteriosis has been described only in three tortoise species. This report involves a captive Hermann's tortoise (Testudo hermanni) diagnosed with cloacal mycobacteriosis and subsequent systemic dissemination by histopathology and PCR. A Mycobacterium sp. belonging to the M. terrae complex was identified as the etiologic agent, and this is the first report of infection in reptiles by this organism.

Comparison of Cytokines Expression from Human Monocyte-Derived Macrophages Infected with Different Species of Mycobacteria.

Cytokines have an important role in mounting effective host immune response against mycobacteria. Latent tuberculosis infection (LTBI) is an indication of containment of mycobacteria by the host immune response, whereas active TB is an indication of a failure of the immune response to contain Mycobacterium tuberculosis. The dynamics of this host-immune response during in vitro infection experiment is believed to be indicative of behavior in the LTBI and active-TB cases. This relationship is, however, not fully elucidated. We investigated the cytokines expression at mRNA and protein level across 2 different protocols, that is, an in vitro protocol comparing human monocyte-derived macrophages (hMDMs; n = 12) infected with different species of mycobacteria, and a clinical protocol comparing TB-Antigen-Nil specimens from LTBI (n = 12) and active-TB (n = 12) cases. We found that in vitro infection of hMDMs with Mycobacterium bovis Bacillus Calmette-Guérin (BCG) and M. tuberculosis R179 showed increased colony-forming units at all time points postinfection. M. bovis BCG-infected hMDMs demonstrated higher levels of 5 cytokines [interferon (IFN)-γ, interleukin (IL)-6, IL-1β, IL-12p40, and IL-12p70] at different intervals compared to M. tuberculosis R179. Compared to LTBI, active-TB cases had higher mRNA expression of IFN-α, IL-6, and IL-8, and lower expression of IFN-γ, IL-1α, IL-1β, IL-4, and tumor necrosis factor-α. Overall, we observed differential host responses at mRNA and protein levels during experimentally controlled in vitro infection, but no prominent differences were observed in the clinical protocol. Therefore, the result of the in vitro experiment model of cytokine response against mycobacteria should be interpreted cautiously when relating to LTBI and active-TB.

Investigating Bacterial Volatilome for the Classification and Identification of Mycobacterial Species by HS-SPME-GC-MS and Machine Learning.

Species of Mycobacteriaceae cause disease in animals and humans, including tuberculosis and leprosy. Individuals infected with organisms in the Mycobacterium tuberculosis complex (MTBC) or non-tuberculous mycobacteria (NTM) may present identical symptoms, however the treatment for each can be different. Although the NTM infection is considered less vital due to the chronicity of the disease and the infrequency of occurrence in healthy populations, diagnosis and differentiation among Mycobacterium species currently require culture isolation, which can take several weeks. The use of volatile organic compounds (VOCs) is a promising approach for species identification and in recent years has shown promise for use in the rapid analysis of both in vitro cultures as well as ex vivo diagnosis using breath or sputum. The aim of this contribution is to analyze VOCs in the culture headspace of seven different species of mycobacteria and to define the volatilome profiles that are discriminant for each species. For the pre-concentration of VOCs, solid-phase micro-extraction (SPME) was employed and samples were subsequently analyzed using gas chromatography–quadrupole mass spectrometry (GC-qMS). A machine learning approach was applied for the selection of the 13 discriminatory features, which might represent clinically translatable bacterial biomarkers.

Mycobacterium tuberculosis Specific Protein Rv1509 Evokes Efficient Innate and Adaptive Immune Response Indicative of Protective Th1 Immune Signature.

Dissecting the function(s) of proteins present exclusively in Mycobacterium tuberculosis (M.tb) will provide important clues regarding the role of these proteins in mycobacterial pathogenesis. Using extensive computational approaches, we shortlisted ORFs/proteins unique to M.tb among 13 different species of mycobacteria and identified a hypothetical protein Rv1509 as a ‘signature protein’ of M.tb. This unique protein was found to be present only in M.tb and absent in all other mycobacterial species, including BCG. In silico analysis identified numerous putative T cell and B cell epitopes in Rv1509. Initial in vitro experiments using innate immune cells demonstrated Rv1509 to be immunogenic with potential to modulate innate immune responses. Macrophages treated with Rv1509 exhibited higher activation status along with substantial release of pro-inflammatory cytokines. Besides, Rv1509 protein boosts dendritic cell maturation by increasing the expression of activation markers such as CD80, HLA-DR and decreasing DC-SIGN expression and this interaction was mediated by innate immune receptor TLR2. Further, in vivo experiments in mice demonstrated that Rv1509 protein promotes the expansion of multifunctional CD4+ and CD8+T cells and induces effector memory response along with evoking a canonical Th1 type of immune response. Rv1509 also induces substantial B cell response as revealed by increased IgG reactivity in sera of immunized animals. This allowed us to demonstrate the diagnostic efficacy of this protein in sera of human TB patients compared to the healthy controls. Taken together, our results reveal that Rv1509 signature protein has immunomodulatory functions evoking immunological memory response with possible implications in serodiagnosis and TB vaccine development.

Current approaches of the treatment of nontuberculous mycobacteriosis

The term nontuberculous mycobacteria (NTM) includes different species of mycobacteria, other than Mycobacterium tuberculosis complex (M. bovis, M. africanum, M. microti, M. canetti, M. caprae, M. pinnipedii, M. suricatta, M. mungi) and other than those that cause leprosy (M. leprae, M. lepromatosis). The rate of lung infection with NTM increases with age and varies considerably in different countries. NTM are opportunistic pathogens that can cause the disease, especially in immunocompromised patients or in those with preexisting lung disease. The decision to initiate the treatment is based on an assessment of the potential risks and benefits, individually for each patient. The aim of the treatment is to liquidate/ improve the clinical and functional manifestations, to reduce the lung lesions and to restore work capacity. The treatment of patients with mycobacteriosis is a complex one (polychemotherapy, if necessary — surgical treatment etc.), long-term, under direct observation, administered in the hospital and/or at home. The treatment regimen is chosen depending on the species involved, radiological picture, comorbidities, drug sensitivity etc.

Occurrence of Mycobacterium spp. in ornamental fish.

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. 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. 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. The obtained results indicate a significant role of ornamental fish as a source of mycobacteria which are potentially dangerous,especially to humans.

Distinct host-immune response toward species related intracellular mycobacterial killing: A transcriptomic study

ABSTRACT The comparison of the host immune response when challenged with pathogenic and nonpathogenic species of mycobacteria can provide answers to the unresolved question of how pathogens subvert or inhibit an effective response. We infected human monocyte derived macrophages (hMDMs) with different species of mycobacteria, in increasing order of pathogenicity, i.e. M. smegmatis, M. bovis BCG, and M. tuberculosis R179 that had been cultured in the absence of detergents. RNA was isolated post-infection and transcriptomic analysis using amplicons (Ampliseq) revealed 274 differentially expressed genes (DEGs) across three species, out of which we selected 19 DEGs for further validation. We used qRT-PCR to confirm the differential expression of 19 DEGs. We studied biological network through Ingenuity Pathway Analysis® (IPA) which revealed up-regulated pathways of the interferon and interleukin family related to the killing of M. smegmatis. Apart from interferon and interleukin family, we found one up-regulated (EIF2AK2) and two down-regulated (MT1A and TRIB3) genes as unique potential targets found by Ampliseq and qRT-PCR which may be involved in the intracellular mycobacterial killing. The roles of these genes have not previously been described in tuberculosis. Multiplex ELISA of culture supernatants showed increased host immune response toward M. smegmatis as compared to M. bovis BCG and M.tb R179. These results enhance our understanding of host immune response against M.tb infection.

Microenvironment of Mycobacterium smegmatis Culture to Induce Cholesterol Consumption Does Cell Wall Remodeling and Enables the Formation of Granuloma-Like Structures.

Pathogenic species of mycobacteria are known to use the host cholesterol during lung infection as an alternative source of carbon and energy. Mycobacteria culture in minimal medium (MM) has been used as an in vitro experimental model to study the consumption of exogenous cholesterol. Once in MM, different species of mycobacteria start to consume the cholesterol and initiate transcriptional and metabolic adaptations, upregulating the enzymes of the methylcitrate cycle (MCC) and accumulating a variety of primary metabolites that are known to be important substrates for cell wall biosynthesis. We hypothesized that stressful pressure of cultures in MM is able to induce critical adaptation for the bacteria which win the infection. To identify important modifications in the biosynthesis of the cell wall, we cultured the fast-growing and nonpathogenic Mycobacterium smegmatis in MM supplemented with or without glycerol and/or cholesterol. Different from the culture in complete medium Middlebrook 7H9 broth, the bacteria when cultured in MM decreased growth and changed in the accumulation of cell wall molecules. However, the supplementation of MM with glycerol and/or cholesterol recovered the accumulation of phosphatidylinositol mannosides (PIMs) and other phospholipids but maintained growth deceleration. The biosynthesis of lipomannan (LM) and of lipoarabinomannan (LAM) was significantly modulated after culture in MM, independently of glycerol and/or cholesterol supplementation, where LM size was decreased (LM13-25KDa) and LAM increased (LAM37-100KDa), when compared these molecules after bacteria culture in complete medium (LM17-25KDa and LAM37-50KDa). These changes modified the cell surface hydrophobicity and susceptibility against H2O2. The infection of J774 macrophages with M. smegmatis, after culture in MM, induced the formation of granuloma-like structures, while supplementation with cholesterol induced the highest rate of formation of these structures. Taken together, our results identify critical changes in mycobacterial cell wall molecules after culture in MM that induces cholesterol accumulation, helping the mycobacteria to increase their capacity to form granuloma-like structures.

Mycobacteria identification in solid culture by inverted phase microscopy and ziehl-neelsen stain

With the aim of identifying morphological differences in colonies of different species of mycobacteria by means of inverted phase microscopy, nine species of high-prevalence pathogenic mycobacteria were seeded in 7H11 solid medium and were observed for up to 21 days. Additionally, Ziehl-Neelsen (ZN) stains were carried out for each one of them. No morphological variations were identified among the species grown on solid medium; however, it was identified that all are able to form cords in solid medium in an early stage of growth, being corroborated by the Ziehl-Neelsen stain in Mycobacterium tuberculosis. so techniques based on detecting M. tuberculosis depending on the identification of the cords should be taken with caution so as not to generate a bad diagnosis, so microbiological characteristics could also be established as a minimum time to detect growth, temperature of growth and bacillary characteristics based on the Ziehl-Neelsen stain for each species studied.

Comparative analysis of volatile organic compounds for the classification and identification of mycobacterial species.

BackgroundSpecies of Mycobacteriaceae cause serious zoonotic diseases in mammals, for example tuberculosis in humans, dogs, parrots, and elephants (caused by Mycobacterium tuberculosis) and in ruminants and humans (caused by M. bovis and M. caprae). Pulmonary diseases, lymphadenitis, skin diseases, and disseminated diseases can be caused by non-tuberculous mycobacteria (NTM). Diagnosis and differentiation among Mycobacterium species are currently done by culture isolation. The established diagnostic protocols comprise several steps that allow species identification. Detecting volatile organic compounds (VOCs) above bacterial cultures is a promising approach towards accelerating species identification via culture isolation. The aims of this project were to analyse VOCs in the headspace above 13 different species of mycobacteria, to define VOC profiles that are unique for each species, and to compile a set of substances that indicate the presence of growing mycobacteria in general.Materials & methodsVOCs were measured in the headspace above 17 different mycobacterial strains, all cultivated on Herrold’s Egg Yolk Medium and above pure media slants that served as controls. For pre-concentration of VOCs, needle-trap micro-extraction was employed. Samples were subsequently analysed using gas chromatography-mass spectrometry. All volatiles were identified and calibrated by analysing pure reference substances.ResultsMore than 130 VOCs were detected in headspace above mycobacteria-inoculated and control slants. Results confirmed significant VOC emissions above all mycobacterial species that had grown well. Concentration changes were measurable in vials with visually assessed bacterial growth and vials without apparent growth. VOCs above mycobacterial cultures could be grouped into substances that were either higher or equally concentrated, lower or equally concentrated, or both as those above control slants. Hence, we were able to identify 17 substances as potential biomarkers of the presence of growing mycobacteria in general.ConclusionsThis study revealed species-specific VOC profiles for eleven species of mycobacteria that showed visually apparent bacterial growth at the time point of analysis.

Non-tuberculous Mycobacteria isolated from lymph nodes and faecal samples of healthy slaughtered cattle and the abattoir environment.

Infections caused by non-tuberculous mycobacteria (NTM) are reported as emerging disease in many countries worldwide. The occurrence of NTM in different hosts and their implication as obligate or opportunistic pathogen remain largely unclear. Lymph nodes and faecal samples of clinically healthy Swiss cattle at slaughter were analysed for the presence of NTM. Based on the examined lymph nodes, NTM were detected in 20% of 108 cattle originating from different premises. The 22 isolates belonged to five different species of Mycobacteria (M.avium subsp. hominissuis, M.kansasii, M.persicum, "M.lymphaticum" and M.europaeum). M.avium subsp. hominissuis (63%) and M.kansasii (18%) thereby predominated and were found in lymph nodes with and without macroscopic changes. Moreover, M.persicum found in two cattle has recently been described as a human pathogen and is closely related to M.kansasii. Amongst cattle with lymph nodes positive for mycobacteria, viable NTM were occasionally also detected in bovine faeces. However, the isolated NTM species from lymph nodes and respective faecal samples (M.hassiacum, M.phlei and M.vaccae) did not coincide. Moreover, NTM species identified amongst isolates from the slaughterhouse environment clearly differed from those from lymph nodes and faecal samples, excluding cross-contamination of the tissue specimens through the environment or laboratory processing. Assuming that some NTM interfere with the detection of bovine tuberculosis (bTB), the present findings in healthy animals emphasize the need of more specific diagnostic tools for bTB eradication programs.

A novel liquid media mycobacteria extraction method for MALDI-TOF MS identification using VITEK® MS

A low-cost identification method that can be performed directly from a positive liquid medium culture is needed for the diagnosis of mycobacterial infections. Here, we describe a novel, cost-effective, and validated method that allows for direct and rapid identification of mycobacteria from a positive liquid culture using VITEK® MS with a total process duration under 45min. From a liquid mycobacteria culture a 3.0mL aliquot is removed 24–72h post positivity and centrifuged to create a pellet. After decanting, the tube is blotted dry, the pellet is re-suspended in 0.5mL of 70% ethanol and then transferred into a 2.0mL tube containing glass beads. Mycobacteria are disrupted mechanically followed by a 10min. incubation at room temperature to complete inactivation. Inactivated material is pelleted by centrifugation and then re-suspended in 10μL of 70% formic acid and 10μL of acetonitrile. After centrifugation, 1μL of supernatant (protein extract) is deposited onto target slide, allowed to dry, and then 1μL CHCA matrix is added.A seeded study was conducted to demonstrate the reliability of the method, a total of 251 culture samples obtained from automated culture systems (BacT/ALERT® MP bottles, BACTEC MGIT™ 960 tubes, and VersaTREK® Myco bottles), were tested and resulted in 98.8% correct identification. Reproducibility was shown by testing three organisms across three reagent lots, between four laboratory technicians, over the course of five days for three liquid media systems resulting in a total of 180 deposits with an overall correct identification of 98.9% with the remaining results giving no identification. Additional studies were performed including comparison of different mechanical disruption techniques, stability of frozen extracts, and stability of slide deposits to allow for flexibility in a routine clinical workflow.The described method proved to be safe while providing consistent and reproducible results for different species of mycobacteria and is compatible with the three most widely used liquid media medium detection systems.

Non-tuberculous mycobacterial empyema in an immunocompetent child

Background: Non-tuberculous mycobacterium (NTM) species are free-living organisms that are ubiquitous in the environment. There are about 100 different species of mycobacteria of which few species cause human disease in immunocompromised individuals. The spectrum of disease caused by NTM range from pulmonary disease including cavity, consolidation , bronchiectasis, lymphadenitis, skin, soft tissue and injection site infections to disseminated disease in immunocompromised individuals. Methods & Materials: We report a 9 years old immunocompetent female patient who presented with Mycobacterium avium intracellulare (MAI) empyema. There have been only two reports to our knowledge regarding NTM in immunocompetent children causing empyema both of which were due to mycobacterium chelonae. Results: A 9 years old girl presented with left sided chest pain for 3 months. There was associated intermittent fever and cough for the last two weeks. Chest X-ray (CXR) revealed massive left sided pleural effusion. Pleural tap drained pus. She underwent thoracotomy and decortication. HIV Elisa was negative. TB MGIT culture at the end of 3 weeks grew non-tuberculous slow growing mycobacteria. Line probe assays revealed MAI. A thorough immune workup showed normal serum levels of IgG and IgM and lymphocyte subset assays. Child was started on clarithromycin, isoniazid, rifampicin and ethambutol. A repeat chest X-ray done after two months showed complete resolution of pleural fluid. Treatment is continued and child is on regular follow up. Conclusion: MAI can lead to tuberculous empyema even in immunocompetent children.

Crohn's disease and related inflammatory diseases: from many single hypotheses to one "superhypothesis"

The aetiology of Crohn’s disease and paratuberculosis are the subjects of intensive study and also frequently, of dispute. However, a number of other nosological entities have a similar history, namely type 1 diabetes, multiple sclerosis, sarcoidosis, asthma, psoriasis, spondylarthritis, Blau syndrom etc. The zoonotic risk of Mycobacterium avium subsp. paratuberculosis (MAP) has been discussed for more than one hundred years. „The problem remains open, further research is needed“, is the sentence which seems to be obligatory in the conclusions of many scientific articles. A number of hypotheses have been suggested, all with a grain of truth in them. The infection hypothesis has many supporters and opponents, but it does not fit to all Crohn’s disease cases. The contribution of the genetic factor has been admitted a long time ago and has been experimentally confirmed by recent excellent studies. An environmental factor is expected and has been often mentioned, but has yet to be discovered. Muramyl dipeptide, derived from peptidoglycans of the bacterial cell wall is one of the triggers, mentioned in connection with chronic inflammatory diseases. The immunomodulatory ability of this compound has been recognised for decades and is exploited in Freund’s adjuvant. A critical amount of muramyl dipeptide can affect immunity during some bacterial infections but the long latent period between infection and onset of the clinical form of the disease could explain why a causative relationship between the primary infection and chronic inflammation is not considered. Different species of mycobacteria can be found in the environment, in water, dust, soil and aerosol. Although severe infections with mycobacteria have been described, these species are not thought to be typical zoonotic pathogens. Muramyl dipeptide derived from mycobacteria obviously plays a starring role as a bacterial trigger in the aetiology of many autoimmune and autoinflammatory diseases. Paratuberculosis in cattle and other ruminants is a source of enormous contamination of the environment but also of milk and meat by MAP. Muramyl dipeptide from mycobacteria, namely MAP, and Crohn’s disease as a representative of diseases often called civilization threats, are important pieces of the gigantic puzzle. Mycobacteria in the environment and foodstuffs have to be acknowledged as a public health risk, which can never be completely eliminated. There is no reason to push the panic button, but we must learn how to live together with this microorganism, how the pool of immunomodulator sources can be diminished, and how the pathogenic relationship between triggers and target tissues can be disrupted. The dissemination of knowledge, the availability of rapid and inexpensive tools for identification of mycobacteria in different matrices, and the establishment of a maximal allowed limit for mycobacteria in milk and meat should contribute to food safety and consumer protection.

Reduction in DNA topoisomerase I level affects growth, phenotype and nucleoid architecture of Mycobacterium smegmatis.

The steady-state negative supercoiling of eubacterial genomes is maintained by the action of DNA topoisomerases. Topoisomerase distribution varies in different species of mycobacteria. While Mycobacterium tuberculosis (Mtb) contains a single type I (TopoI) and a single type II (Gyrase) enzyme, Mycobacterium smegmatis (Msm) and other members harbour additional relaxases. TopoI is essential for Mtb survival. However, the necessity of TopoI or other relaxases in Msm has not been investigated. To recognize the importance of TopoI for growth, physiology and gene expression of Msm, we have developed a conditional knock-down strain of TopoI in Msm. The TopoI-depleted strain exhibited extremely slow growth and drastic changes in phenotypic characteristics. The cessation of growth indicates the essential requirement of the enzyme for the organism in spite of having additional DNA relaxation enzymes in the cell. Notably, the imbalance in TopoI level led to the altered expression of topology modulatory proteins, resulting in a diffused nucleoid architecture. Proteomic and transcript analysis of the mutant indicated reduced expression of the genes involved in central metabolic pathways and core DNA transaction processes. RNA polymerase (RNAP) distribution on the transcription units was affected in the TopoI-depleted cells, suggesting global alteration in transcription. The study thus highlights the essential requirement of TopoI in the maintenance of cellular phenotype, growth characteristics and gene expression in mycobacteria. A decrease in TopoI level led to altered RNAP occupancy and impaired transcription elongation, causing severe downstream effects.

Zafirlukast Inhibits Complexation of Lsr2 with DNA and Growth of Mycobacterium tuberculosis

The mycobacterial nucleoid-associated protein Lsr2 is a DNA-bridging protein that plays a role in condensation and structural organization of the genome and acts as a global repressor of gene transcription. Here we describe experiments demonstrating that zafirlukast inhibits the complexation between Lsr2 and DNA in vitro. Zafirlukast is shown to inhibit growth in two different species of mycobacteria tested but exhibits no growth inhibition of Escherichia coli. The Lsr2 inhibitory activity is reflected in vivo as determined by monitoring of transcription levels in Mycobacterium tuberculosis. These data suggest that zafirlukast inhibits Lsr2 function in vivo, promoting dysregulation of the expression of an array of genes typically bound by Lsr2 and hindering growth. Since zafirlukast likely operates by a mechanism distinct from current M. tuberculosis drugs and is currently used as a prophylactic treatment for asthma, it offers an intriguing lead for development of new treatments for tuberculosis.

Structural determination of glycopeptidolipids of Mycobacterium smegmatis by high‐resolution multiple‐stage linear ion‐trap mass spectrometry with electrospray ionization

Glycopeptidolipids (GPLs) are abundant in the cell walls of different species of mycobacteria and consist of tripeptide-amino-alcohol core of D-Phe-D-allo-Thr-D-Ala-L-alaninol linked to 3-hydroxy or 3-methoxy C(26-34) fatty acyl chain at the N-terminal of D-Phe via amide linkage, and a 6-deoxytalose (6-dTal) and an O-methyl rhamnose residues, respectively, attach to D-allo-Thr and the terminal L-alaninol. They are important cell-surface antigens that are implicated in the pathogenesis of opportunistic mycobacteria belonging to the Mycobacterium avium complex. In this contribution, we described multiple-stage linear ion trap in conjunction with high-resolution mass spectrometry towards structural characterization of complex GPLs as [M + Na](+) ions isolated from Mycobacterium smegmatis, a fast-growing and non-pathogenic mycobacterial species. Following resonance excitation in an ion trap, MS(n) spectra of the [M + Na](+) ions of GPLs contained mainly b and y series ions that readily determine the peptide sequence. Fragment ions from MS(n) also afford locating the 6-dTal and O-methyl rhamnose residues linked to the D-allo-Thr and terminal L-alaninol of the peptide core, respectively, as well as recognizing the modifications of the glycosides, including their acetylation and methylation states and the presence of succinyl group. The GPL families consisting of 3-hydroxy fatty acyl and of 3-methoxy fatty acyl substituents are readily distinguishable. The MS profiles of the GPLs from cells are dependant on the conditions they were grown, and several isobaric isomers were identified for many of the molecular species. These multiple-stage mass spectrometric approaches give detailed structures of GPL in complex mixtures of which the isomeric structures are difficult to define using other analytical methods.

First Description of Natural and Experimental Conjugation between Mycobacteria Mediated by a Linear Plasmid

BackgroundIn a previous study, we detected the presence of a Mycobacterium avium species-specific insertion sequence, IS1245, in Mycobacterium kansasii. Both species were isolated from a mixed M. avium-M. kansasii bone marrow culture from an HIV-positive patient. The transfer mechanism of this insertion sequence to M. kansasii was investigated here.Methodology/Principal FindingsA linear plasmid (pMA100) was identified in all colonies isolated from the M. avium-M. kansasii mixed culture carrying the IS1245 element. The linearity of pMA100 was confirmed. Other analyses suggested that pMA100 contained a covalently bound protein in the terminal regions, a characteristic of invertron linear replicons. Partial sequencing of pMA100 showed that it bears one intact copy of IS1245 inserted in a region rich in transposase-related sequences. These types of sequences have been described in other linear mycobacterial plasmids. Mating experiments were performed to confirm that pMA100 could be transferred in vitro from M. avium to M. kansasii. pMA100 was transferred by in vitro conjugation not only to the M. kansasii strain from the mixed culture, but also to two other unrelated M. kansasii clinical isolates, as well as to Mycobacterium bovis BCG Moreau.Conclusions/SignificanceHorizontal gene transfer (HGT) is one of most important mechanisms leading to the evolution and diversity of bacteria. This work provides evidence for the first time on the natural occurrence of HGT between different species of mycobacteria. Gene transfer, mediated by a novel conjugative plasmid, was detected and experimentally reproduced.