(1/2326) Generation of CD8(+) T-cell responses to Mycobacterium bovis and mycobacterial antigen in experimental bovine tuberculosis.
Protective immunity against tuberculosis is considered to be essentially cell mediated, and an important role for CD8(+) T lymphocytes has been suggested by several studies of murine and human infections. The present work, using an experimental model of infection with Mycobacterium bovis in cattle, showed that live M. bovis elicits the activation of CD8(+) T cells in vitro. However, a sonic extract prepared from M. bovis (MBSE) and protein purified derivative (PPDb) also induced a considerable degree of activation of the CD8(+) T cells. Analysis of proliferative responses of peripheral blood mononuclear cells, purified CD8(+) T cells, and CD8(+) T-cell clones to M. bovis and to soluble antigenic preparations (MBSE, PPDb) showed that the responses of all three types of cells were always superior for live mycobacteria but that strong responses were also obtained with complex soluble preparations. Furthermore, while cytotoxic capabilities were not investigated, the CD8(+) T cells were found to produce and release gamma interferon in response to antigen (live and soluble), which indicated one possible protective mechanism for these cells in bovine tuberculosis. Finally, it was demonstrated by metabolic inhibition with brefeldin A and cytochalasin D at the clonal level that an endogenous pathway of antigen processing is required for presentation to bovine CD8(+) cells and that presentation is also dependent on phagocytosis of the antigen. (+info)
(2/2326) Fluoroquinolone action against clinical isolates of Mycobacterium tuberculosis: effects of a C-8 methoxyl group on survival in liquid media and in human macrophages.
When the lethal action of a C-8 methoxyl fluoroquinolone against clinical isolates of Mycobacterium tuberculosis in liquid medium was measured, the compound was found to be three to four times more effective (as determined by measuring the 90% lethal dose) than a C-8-H control fluoroquinolone or ciprofloxacin against cells having a wild-type gyrA (gyrase) gene. Against ciprofloxacin-resistant strains, the C-8 methoxyl group enhanced lethality when alanine was replaced by valine at position 90 of the GyrA protein or when aspartic acid 94 was replaced by glycine, histidine, or tyrosine. During infection of a human macrophage model by wild-type Mycobacterium bovis BCG, the C-8 methoxyl group lowered survival 20- to 100-fold compared with the same concentration of a C-8-H fluoroquinolone. The C-8 methoxyl fluoroquinolone was also more effective than ciprofloxacin against a gyrA Asn94 mutant of M. bovis BCG. In an M. tuberculosis-macrophage system the C-8 methoxyl group improved fluoroquinolone action against both quinolone-susceptible and quinolone-resistant clinical isolates. Thus, a C-8 methoxyl group enhances the bactericidal activity of quinolones with N1-cyclopropyl substitutions; these data encourage further refinement of fluoroquinolones as antituberculosis agents. (+info)
(3/2326) Observations on animal and human health during the outbreak of Mycobacterium bovis in game farm wapiti in Alberta.
This report describes and discusses the history, clinical, pathologic, epidemiologic, and human health aspects of an outbreak of Mycobacterium bovis infection in domestic wapiti in Alberta between 1990 and 1993, shortly after legislative changes allowing game farming. The extent and seriousness of the outbreak of M. bovis in wapiti in Alberta was not fully known at its onset. The clinical findings in the first recognized infected wapiti are presented and the postmortem records for the herd in which the animal resided are summarized. Epidemiologic findings from the subsequent field investigation are reviewed, the results of recognition and investigation of human exposure are updated, and recommendations for reduction of human exposure are presented. (+info)
(4/2326) Molecular markers demonstrate that the first described multidrug-resistant Mycobacterium bovis outbreak was due to Mycobacterium tuberculosis.
We genetically characterized multidrug-resistant Mycobacterium tuberculosis complex strains which caused a nosocomial outbreak of tuberculosis affecting six human immunodeficiency virus (HIV)-positive patients and one HIV-negative staff member (E. Bouvet, E. Casalino, G. Mendoza-Sassi, S. Lariven, E. Vallee, M. Pernet, S. Gottot, and F. Vachon, AIDS 7:1453-1460, 1993). The strains showed all the phenotypic characteristics of Mycobacterium bovis. They presented a high copy number of IS6110, the spacers 40 to 43 in the direct repeat locus, and the mtp40 fragment. They lacked the G-A mutation at position 285 in the oxyR gene and the C-G mutation at position 169 in the pncA gene. These genetic characteristics revealed that these were dysgonic, slow-growing M. tuberculosis strains mimicking the M. bovis phenotype, probably as a consequence of cellular alterations associated with the multidrug resistance. Spoligotyping and IS6110 restriction fragment length polymorphism (RFLP) analysis confirmed that the outbreak was due to a single strain. However, the IS6110 RFLP pattern of the strain isolated from the last patient, diagnosed three years after the index case, differed slightly from the patterns of the other six strains. A model of a possible genetic event is presented to explain this divergence. This study stresses the value of using several independent molecular markers to identify multidrug-resistant tubercle bacilli. (+info)
(5/2326) Characterization of exochelins of the Mycobacterium bovis type strain and BCG substrains.
Pathogenic mycobacteria must acquire iron in the host in order to multiply and cause disease. To do so, they release abundant quantities of siderophores called exochelins, which have the capacity to scavenge iron from host iron-binding proteins and deliver it to the mycobacteria. In this study, we have characterized the exochelins of Mycobacterium bovis, the causative agent of bovine and occasionally of human tuberculosis, and the highly attenuated descendant of M. bovis, bacillus Calmette-Guerin (BCG), widely used as a vaccine against human tuberculosis. The M. bovis type strain, five substrains of M. bovis BCG (Copenhagen, Glaxo, Japanese, Pasteur, and Tice), and two strains of virulent Mycobacterium tuberculosis all produce the same set of exochelins, although the relative amounts of individual exochelins may differ. Among these mycobacteria, the total amount of exochelins produced is greatest in M. tuberculosis, intermediate in M. bovis, and smallest in M. bovis BCG. (+info)
(6/2326) Characterization of mannooligosaccharide caps in mycobacterial lipoarabinomannan by capillary electrophoresis/electrospray mass spectrometry.
A new analytical approach based on capillary electrophoresis-electrospray mass spectrometry (CE/ESI-MS) has provided new insight into the characterization of mannooligosaccharide caps from lipoarabinomannans (LAMs), which are key molecules in the immunopathogenesis of tuberculosis. This analytical approach requires oligosaccharide labeling with the fluorophore 1-aminopyrene-3,6,8-trisulfonate (APTS) by reductive amination at the reducing termini. Optimization of the separation and ionization conditions, such as the choice of capillary electrophoresis (CE) electrolyte buffers, is presented and discussed. Anionic separation of the mono and oligosaccharide APTS derivatives was finally achieved with aqueous triethylammonium formate buffer. It was found that in contrast to the triethylammonium phosphate buffer, the triethylammonium formate buffer was appropriate for CE/ESI-MS coupling analysis of APTS-carbohydrate derivatives. In this case, negative ESI-mass spectra of APTS-carbohydrate adducts showed mainly (M-2H)2-pseudomolecular ions and some sequence fragment ions allowing their non-ambiguous structural characterization at the picomolar level. This analytical approach was successfully applied to more complex mixtures of carbohydrates released by mild acid hydrolysis of the lipoarabinomannans from Mycobacterium bovis BCG. The APTS-mannooligosaccharide cap adducts were separated by CE and their structural characterization achieved by CE/ESI-MS analyses. Mannooligosaccharide caps were routinely analyzed by capillary electrophoresis-laser induced fluorescence (CE-LIF) from 50 fmol of lipoarabinomannans with mannosyl capping (ManLAMs) but sensitivity was about 50 times lower using ESI-MS detection. (+info)
(7/2326) Oxygen depletion-induced dormancy in Mycobacterium bovis BCG.
Gradual depletion of oxygen causes the shift-down of aerobic growing Mycobacterium bovis BCG to an anaerobic synchronized state of nonreplicating persistence. The persistent culture shows induction of glycine dehydrogenase and alpha-crystallin-like protein and is sensitive to metronidazole. (+info)
(8/2326) Different strategies for molecular differentiation of Mycobacterium bovis strains isolated in Sardinia, Italy.
Different genetic markers were used to analyze 22 Mycobacterium bovis strains isolated from cattle in Sardinia and one human isolate. IS6110 DNA fingerprinting differentiated the strains into six patterns, whereas with enterobacterial repetitive consensus sequence primers produced seven clusters. PCR ribotyping followed by digestion with HaeIII and PvuII produced five and seven patterns, respectively. PCR with the (GTG)5 oligonucleotide primer showed the best discriminatory power, generating eight clusters among the strains analyzed. (+info)