The Experts below are selected from a list of 48663 Experts worldwide ranked by ideXlab platform
Vojo Deretic - One of the best experts on this subject based on the ideXlab platform.
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mechanism of inducible nitric oxide synthase exclusion from Mycobacterial phagosomes
PLOS Pathogens, 2007Co-Authors: Alexander S Davis, Isabelle Vergne, Sharon Master, Jennifer Chua, George B. Kyei, Vojo DereticAbstract:Mycobacterium tuberculosis is sensitive to nitric oxide generated by inducible nitric oxide synthase (iNOS). Consequently, to ensure its survival in macrophages, M. tuberculosis inhibits iNOS recruitment to its phagosome by an unknown mechanism. Here we report the mechanism underlying this process, whereby Mycobacteria affect the scaffolding protein EBP50, which normally binds to iNOS and links it to the actin cytoskeleton. Phagosomes harboring live Mycobacteria showed reduced capacity to retain EBP50, consistent with lower iNOS recruitment. EBP50 was found on purified phagosomes, and its expression increased upon macrophage activation, paralleling expression changes seen with iNOS. Overexpression of EBP50 increased while EBP50 knockdown decreased iNOS recruitment to phagosomes. Knockdown of EBP50 enhanced Mycobacterial survival in activated macrophages. We tested another actin organizer, coronin-1, implicated in mycobacterium-macrophage interaction for contribution to iNOS exclusion. A knockdown of coronin-1 resulted in increased iNOS recruitment to model latex bead phagosomes but did not increase iNOS recruitment to phagosomes with live Mycobacteria and did not affect Mycobacterial survival. Our findings are consistent with a model for the block in iNOS association with Mycobacterial phagosomes as a mechanism dependent primarly on reduced EBP50 recruitment.
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rab14 is critical for maintenance of mycobacterium tuberculosis phagosome maturation arrest
The EMBO Journal, 2006Co-Authors: George B. Kyei, Isabelle Vergne, Jennifer Chua, Esteban A Roberts, J S Harris, Jagath R Junutula, Vojo DereticAbstract:Mycobacterium tuberculosis arrests phagosomal maturation in infected macrophage, and, apart from health significance, provides a superb model system to dissect the phagolysosomal biogenesis pathway. Here, we demonstrate a critical role for the small GTPase Rab14 in maintaining Mycobacterial phagosome maturation block. Four-dimensional microscopy showed that phagosomes containing live Mycobacteria accumulated Rab14 following phagocytosis. The recruitment of Rab14 had strong functional consequence, as a knockdown of endogenous Rab14 by siRNA or overexpression of Rab14 dominant-negative mutants (Rab14S25N and Rab14N125I) released the maturation block and allowed phagosomes harboring live Mycobacteria to progress into phagolysosomes. Conversely, overexpression of the wild-type Rab14 and the constitutively active mutant Rab14Q70L prevented phagosomes with dead Mycobacteria from undergoing default maturation into phagolysosomal organelles. Mechanistic studies demonstrated a role for Rab14 in stimulating organellar fusion between phagosomes and early endosomes but not with late endosomes. Rab14 enables Mycobacterial phagosomes to maintain early endosomal characteristics and avoid late endosomal/lysosomal degradative components.
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oxidative stress response and characterization of the oxyr ahpc and fura katg loci in mycobacterium marinum
Journal of Bacteriology, 1998Co-Authors: Eileen Paganramos, Jian Song, M Mcfalone, M H Mudd, Vojo DereticAbstract:Oxidative stress response in pathogenic Mycobacteria is believed to be of significance for host-pathogen interactions at various stages of infection. It also plays a role in determining the intrinsic susceptibility to isoniazid in Mycobacterial species. In this work, we characterized the oxyR-ahpC and furA-katG loci in the nontuberculous pathogen Mycobacterium marinum. In contrast to Mycobacterium smegmatis and like Mycobacterium tuberculosis and Mycobacterium leprae, M. marinum was shown to possess a closely linked and divergently oriented equivalents of the regulator of peroxide stress response oxyR and its subordinate gene ahpC, encoding a homolog of alkyl hydroperoxide reductase. Purified Mycobacterial OxyR was found to bind to the oxyR-ahpC promoter region from M. marinum and additional Mycobacterial species. Mobility shift DNA binding analyses using OxyR binding sites from several Mycobacteria and a panel of in vitro-generated mutants validated the proposed consensus Mycobacterial recognition sequence. M. marinum AhpC levels detected by immunoblotting, were increased upon treatment with H2O2, in keeping with the presence of a functional OxyR and its binding site within the promoter region of ahpC. In contrast, OxyR did not bind to the sequences upstream of the katG structural gene, and katG expression did not follow the pattern seen with ahpC. Instead, a new open reading frame encoding a homolog of the ferric uptake regulator Fur was identified immediately upstream of katG in M. marinum. The furA-katG linkage and arrangement are ubiquitous in Mycobacteria, suggesting the presence of additional regulators of oxidative stress response and potentially explaining the observed differences in ahpC and katG expression. Collectively, these findings broaden our understanding of oxidative stress response in Mycobacteria. They also suggest that M. marinum will be useful as a model system for studying the role of oxidative stress response in Mycobacterial physiology, intracellular survival, and other host-pathogen interactions associated with Mycobacterial diseases.
Michele Trucksis - One of the best experts on this subject based on the ideXlab platform.
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pathogenicity of mycobacterium fortuitum and mycobacterium smegmatis to goldfish carassius auratus
Veterinary Microbiology, 1999Co-Authors: Adel M Talaat, Michele Trucksis, Andrew S Kane, Renate ReimschuesselAbstract:Despite the ubiquitous presence of atypical Mycobacteria in the environment and the potential risk of infection in humans and animals, the pathogenesis of diseases caused by infection with atypical Mycobacteria has been poorly characterized. In this study, goldfish, Carassius auratus were infected either with the rapidly growing fish pathogen, Mycobacterium fortuitum or with another rapidly growing Mycobacteria, Mycobacterium smegmatis. Bacterial persistence and pathological host response to Mycobacterial infection in the goldfish are described. Mycobacteria were recovered from a high percentage of inoculated fish that developed a characteristic chronic granulomatous response similar to that associated with natural Mycobacterial infection. Both M. fortuitum and M. smegmatis were pathogenic to fish. Fish infected with M. smegmatis ATCC 19420 showed the highest level of giant cell recruitment compared to fish inoculated with M. smegmatis mc2155 and M. fortuitum. Of the three strains of Mycobacteria examined, M. smegmatis ATCC 19420 was the most virulent strain to goldfish followed by M. fortuitum and M. smegmatis mc2155, respectively.
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identification of Mycobacteria infecting fish to the species level using polymerase chain reaction and restriction enzyme analysis
Veterinary Microbiology, 1997Co-Authors: Adel M Talaat, Michele Trucksis, Renate ReimschuesselAbstract:An assay is described utilizing PCR technology for a rapid diagnostic test to identify fish infection with Mycobacterium marinum, M. fortuitum and M. chelonae. A 924 bp DNA fragment from a highly conserved area of the Mycobacterial 16S rRNA gene was amplified using Mycobacteria genus-specific primers and digested with restriction enzymes (BanI and ApaI). This examination yielded unique restriction patterns for each Mycobacterial specie enabling identification of Mycobacteria infecting fish to the species level. The protocol can be applied to purified DNA, a simple colony preparation or infected fish tissue. This protocol can be completed in 1-2 days.
Joseph O Falkinham - One of the best experts on this subject based on the ideXlab platform.
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health impacts of environmental Mycobacteria
Clinical Microbiology Reviews, 2004Co-Authors: Todd P Primm, Christie A Lucero, Joseph O FalkinhamAbstract:Environmental Mycobacteria are emerging pathogens causing opportunistic infections in humans and animals. The health impacts of human-Mycobacterial interactions are complex and likely much broader than currently recognized. Environmental Mycobacteria preferentially survive chlorination in municipal water, using it as a vector to infect humans. Widespread chlorination of water has likely selected more resistant environmental Mycobacteria species and potentially explains the shift from M. scrofulaceum to M. avium as a cause of cervical lymphadenitis in children. Thus, human activities have affected Mycobacterial ecology. While the slow growth and hydrophobicity of environmental Mycobacteria appear to be disadvantages, the unique cell wall architecture also grants high biocide and antibiotic resistance, while hydrophobicity facilitates nutrient acquisition, biofilm formation, and spread by aerosolization. The remarkable stress tolerance of environmental Mycobacteria is the major reason they are human pathogens. Environmental Mycobacteria invade protozoans, exhibiting parasitic and symbiotic relationships. The molecular mechanisms of Mycobacterial intracellular pathogenesis in animals likely evolved from similar mechanisms facilitating survival in protozoans. In addition to outright infection, environmental Mycobacteria may also play a role in chronic bowl diseases, allergies, immunity to other pulmonary infections, and the efficacy of bacillus Calmette-Guerin vaccination.
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factors influencing numbers of mycobacterium avium mycobacterium intracellulare and other Mycobacteria in drinking water distribution systems
Applied and Environmental Microbiology, 2001Co-Authors: Joseph O Falkinham, Cheryl D Norton, Mark W LechevallierAbstract:Eight water distribution systems were sampled over an 18-month period (528 water and 55 biofilm samples) to measure the frequency of recovery and number of Mycobacteria, particularly Mycobacterium avium and Mycobacterium intracellulare, in raw source waters before and after treatment and within the distribution system. The systems were chosen to assess the influence of source water, treatment, and assimilable organic carbon levels on Mycobacterial numbers. Overall, Mycobacterial recovery from the systems was low (15% of samples). Numbers of Mycobacteria ranged from 10 to 700,000 CFU liter(-1). The number of M. avium in raw waters was correlated with turbidity. Water treatment substantially reduced the number of Mycobacteria in raw waters by 2 to 4 log units. Mycobacterial numbers were substantially higher in the distribution system samples (average, 25,000-fold) than in those collected immediately downstream from the treatment facilities, indicating that Mycobacteria grow in the distribution system. The increase in Mycobacterial numbers was correlated with assimilable organic carbon and biodegradable organic carbon levels (r(2) = 0.65, P = 0.03). Although M. intracellulare was seldom recovered from water samples, it was frequently recovered (six of eight systems) in high numbers from biofilms (average, 600 CFU/cm(2)). Evidently, the ecological niches of M. avium and M. intracellulare are distinct.
Mark W Lechevallier - One of the best experts on this subject based on the ideXlab platform.
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factors influencing numbers of mycobacterium avium mycobacterium intracellulare and other Mycobacteria in drinking water distribution systems
Applied and Environmental Microbiology, 2001Co-Authors: Joseph O Falkinham, Cheryl D Norton, Mark W LechevallierAbstract:Eight water distribution systems were sampled over an 18-month period (528 water and 55 biofilm samples) to measure the frequency of recovery and number of Mycobacteria, particularly Mycobacterium avium and Mycobacterium intracellulare, in raw source waters before and after treatment and within the distribution system. The systems were chosen to assess the influence of source water, treatment, and assimilable organic carbon levels on Mycobacterial numbers. Overall, Mycobacterial recovery from the systems was low (15% of samples). Numbers of Mycobacteria ranged from 10 to 700,000 CFU liter(-1). The number of M. avium in raw waters was correlated with turbidity. Water treatment substantially reduced the number of Mycobacteria in raw waters by 2 to 4 log units. Mycobacterial numbers were substantially higher in the distribution system samples (average, 25,000-fold) than in those collected immediately downstream from the treatment facilities, indicating that Mycobacteria grow in the distribution system. The increase in Mycobacterial numbers was correlated with assimilable organic carbon and biodegradable organic carbon levels (r(2) = 0.65, P = 0.03). Although M. intracellulare was seldom recovered from water samples, it was frequently recovered (six of eight systems) in high numbers from biofilms (average, 600 CFU/cm(2)). Evidently, the ecological niches of M. avium and M. intracellulare are distinct.
Renate Reimschuessel - One of the best experts on this subject based on the ideXlab platform.
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pathogenicity of mycobacterium fortuitum and mycobacterium smegmatis to goldfish carassius auratus
Veterinary Microbiology, 1999Co-Authors: Adel M Talaat, Michele Trucksis, Andrew S Kane, Renate ReimschuesselAbstract:Despite the ubiquitous presence of atypical Mycobacteria in the environment and the potential risk of infection in humans and animals, the pathogenesis of diseases caused by infection with atypical Mycobacteria has been poorly characterized. In this study, goldfish, Carassius auratus were infected either with the rapidly growing fish pathogen, Mycobacterium fortuitum or with another rapidly growing Mycobacteria, Mycobacterium smegmatis. Bacterial persistence and pathological host response to Mycobacterial infection in the goldfish are described. Mycobacteria were recovered from a high percentage of inoculated fish that developed a characteristic chronic granulomatous response similar to that associated with natural Mycobacterial infection. Both M. fortuitum and M. smegmatis were pathogenic to fish. Fish infected with M. smegmatis ATCC 19420 showed the highest level of giant cell recruitment compared to fish inoculated with M. smegmatis mc2155 and M. fortuitum. Of the three strains of Mycobacteria examined, M. smegmatis ATCC 19420 was the most virulent strain to goldfish followed by M. fortuitum and M. smegmatis mc2155, respectively.
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identification of Mycobacteria infecting fish to the species level using polymerase chain reaction and restriction enzyme analysis
Veterinary Microbiology, 1997Co-Authors: Adel M Talaat, Michele Trucksis, Renate ReimschuesselAbstract:An assay is described utilizing PCR technology for a rapid diagnostic test to identify fish infection with Mycobacterium marinum, M. fortuitum and M. chelonae. A 924 bp DNA fragment from a highly conserved area of the Mycobacterial 16S rRNA gene was amplified using Mycobacteria genus-specific primers and digested with restriction enzymes (BanI and ApaI). This examination yielded unique restriction patterns for each Mycobacterial specie enabling identification of Mycobacteria infecting fish to the species level. The protocol can be applied to purified DNA, a simple colony preparation or infected fish tissue. This protocol can be completed in 1-2 days.
