Tuberculosis In Mammals Research Articles

Autophagy restricts Mycobacterium tuberculosis during acute infection in mice.

Whether or not autophagy has a role in defence against Mycobacterium tuberculosis infection remains unresolved. Previously, conditional knockdown of the core autophagy component ATG5 in myeloid cells was reported to confer extreme susceptibility to M. tuberculosis in mice, whereas depletion of other autophagy factors had no effect on infection. We show that doubling cre gene dosage to more robustly deplete ATG16L1 or ATG7 resulted in increased M. tuberculosis growth and host susceptibility in mice, although ATG5-depleted mice are more sensitive than ATG16L1- or ATG7-depleted mice. We imaged individual macrophages infected with M. tuberculosis and identified a shift from apoptosis to rapid necrosis in autophagy-depleted cells. This effect was dependent on phagosome permeabilization by M. tuberculosis. We monitored infected cells by electron microscopy, showing that autophagy protects the host macrophage by partially reducing mycobacterial access to the cytosol. We conclude that autophagy has an important role in defence against M. tuberculosis in mammals.

First report of Mycobacterium bovis in wild chacma baboons (Papio ursinus) at the human-wildlife interface area in Zambia.

Mycobacterium bovis (M.bovis) causes tuberculosis in mammals and is a major public health threat worldwide. While M.bovis has been reported in humans, domestic and wild ruminants at the human-wildlife-livestock interface area in Zambia, there is paucity of information on the role of primates as reservoir hosts. We screened seven wild chacma baboons (Papio ursinus) for tuberculosis at the human-wildlife interface area in Lochinvar National Park in the Kafue Flats, Zambia. Following necropsy, lung tissue and associated lymph nodes with tuberculous-like lesions collected from four adult male baboons were prepared for Mycobacterium culture. The isolates were initially typed using the Mycobacterium tuberculosis complex-discrimination multiplex PCR assay and further characterized by spoligotyping and 26-loci MIRU-VNTR. Mycobacteria were isolated from all four animals and identified as M.bovis by PCR. On Spoligotyping, all isolates belonged to SB 0120 spoligotype, which is similar to what was previously reported in humans, cattle and Kafue lechwe antelopes in Kafue Flats ecosystem. Furthermore, on MIRU-VNTR typing, the baboon isolates clustered with cattle and Kafue lechwe isolates from the same catchment area. This finding intimates probable cross-species transmission of M.bovis in the Kafue Flats ecosystem. Due to the close interaction of baboons and humans at interface areas in Zambia, our results have potential implications for public health. Equally, this finding raises concerns for conservation.

TUBERCULOUS AND NONTUBERCULOUS MYCOBACTERIA IN HUMAN AND ANIMAL INFECTION

Within the genus Mycobacterium (M.) more than 170 different types ofmycobacteria have been identified. In relation to humans, they are divided into threegroups. M. tuberculosis complex, which includes ten species that cause tuberculosisin mammals. The type of M. tuberculosis within M. tuberculosis complex remainsthe major cause of tuberculosis in humans in the world. Except for a long time knownspecies (M. bovis, M. africanum, M. microti, M. canetti, M. caprae), new membersof the group have recently been discovered. M. pinnipedii in seals, M. munghi inmongoose, M. orygis in arabian oryx and M. suricattae in the meerkat. The samecauses have been proven in people living nearby. M. leprae is the cause of theleprosy in humans. The disease has been proven in nine banded armadillos (Dasypusnovemcinctus) and represents the natural reservoir of M. leprae. The largest numberof mycobacteria (more than 160 species) belongs to nontuberculous mycobacteria.They are found in the environment, they are very resistant and adapted to growthand development, and to humans and animals are often exposed to them. Someare important potentially pathogenic species and they sometimes cause severepathological processes in humans and animals.

Evaluation of Tissue Fixation Methods to Inactivate Mycobacterium bovis Under Routine Laboratory Conditions

Mycobacterium bovis (M. bovis) is the etiologic agent of tuberculosis in mammals, including humans. The seriousness of disease and low infective dose require that the agent be handled under biosafe...

Designing Polymerase Chain Reaction (PCR) Technique for the Detection of Specific Causes of Tuberculosis (TB) in Dairy Cattle and Human

Designing Polymerase Chain Reaction (PCR) Technique for the Detection of Specific Causes of Tuberculosis (TB) in Dairy Cattle and Human Tuberculosis (TB) in cattle and human is caused by M. bovis, M. tuberculosis and M. avium subsp. var Paratuberculosis (M. paratuberculosis). Selected dairy cattle (N=700) and human (N=20) were tested using tuberculin tests and X-ray imaging. Aspiration biopsy of prescapular lymphnodes from tuberculin test positive cattle and urine, cough, pleural and peritoneal fluid from suspected human was further tested using Ziehl Neelsen staining. Genomic DNA from tuberculin test positive cattle (N=23) and suspected humans (N=20) were tested using multiplex polymerase chain reactions (PCR) targeting 16srRNA (1030bp, 180bp). Results showed that 23 cattle and 11 human were infected with TB. To detect infectivity due to M. bovis and M. tuberculosis selected cattle (N=11) and humans (N=11) samples were tested in uniplex PCR targeting MPB83 (600bp) and H37Rv Rv3479HP (667bp) genes respectively. Results of PCR showed that all of the bovine and seven human samples generated MPB83 gene specific 600bp amplicon. Two bovine and seven human DNA generated H37Rv Rv3479HP gene specific 667bp amplicons. Seven cattle were infected with M. bovis and two with M. tuberculosis. Two cattle were co-infected with M. bovis and M. paratuberculosis. Four humans were infected with M. bovis and seven with M. tuberculosis. The MPB83 gene is invariably shared by M. bovis and M. tuberculosis. The PCR protocol designed targeting fragment of H37Rv Rv3479HP (667bp) gene is selective for M. tuberculosis. Results of sequencing showed point mutation in 16srRNA, MPB83 and H37Rv Rv3479HP genes. Phylogenetic analyses of the selected genes of M. bovis and M. tuberculosis showed that the organisms were belonging to Lineage 1. Intradermal tuberculin test and smear microscopy unable to differentiate infectivity due to M. bovis or M. tuberculosis. The PCR technique designed appear specific for M. tuberculosis, can be used to detect causes of TB in mammals and designing future preventive strategies accordingly.

Revisiting Host Preference in the Mycobacterium tuberculosis Complex: Experimental Infection Shows M. tuberculosis H37Rv to Be Avirulent in Cattle

Experiments in the late 19th century sought to define the host specificity of the causative agents of tuberculosis in mammals. Mycobacterium tuberculosis, the human tubercle bacillus, was independently shown by Smith, Koch, and von Behring to be avirulent in cattle. This finding was erroneously used by Koch to argue the converse, namely that Mycobacterium bovis, the agent of bovine tuberculosis, was avirulent for man, a view that was subsequently discredited. However, reports in the literature of M. tuberculosis isolation from cattle with tuberculoid lesions suggests that the virulence of M. tuberculosis for cattle needs to be readdressed. We used an experimental bovine infection model to test the virulence of well-characterized strains of M. tuberculosis and M. bovis in cattle, choosing the genome-sequenced strains M. tuberculosis H37Rv and M. bovis 2122/97. Cattle were infected with approximately 106 CFU of M. tuberculosis H37Rv or M. bovis 2122/97, and sacrificed 17 weeks post-infection. IFN-γ and tuberculin skin tests indicated that both M. bovis 2122 and M. tuberculosis H37Rv were equally infective and triggered strong cell-mediated immune responses, albeit with some indication of differential antigen-specific responses. Postmortem examination revealed that while M. bovis 2122/97–infected animals all showed clear pathology indicative of bovine tuberculosis, the M. tuberculosis–infected animals showed no pathology. Culturing of infected tissues revealed that M. tuberculosis was able to persist in the majority of animals, albeit at relatively low bacillary loads. In revisiting the early work on host preference across the M. tuberculosis complex, we have shown M. tuberculosis H37Rv is avirulent for cattle, and propose that the immune status of the animal, or genotype of the infecting bacillus, may have significant bearing on the virulence of a strain for cattle. This work will serve as a baseline for future studies into the genetic basis of host preference, and in particular the molecular basis of virulence in M. bovis.

Bovine tuberculosis in domestic and wild mammals in an area of Dorset. III. The prevalence of tuberculosis in mammals other than badgers and cattle.

A large sample of the wild mammals found on a farm in South Dorset were trapped and examined for the presence of Mycobacterium bovis following the discovery of widespread infection in cattle and badgers. M. bovis was isolated from the lymph nodes of two out of 90 rats (rattus norvegicus) and one out of seven foxes (Vulpes vulpes) but no lesions of tuberculosis were observed. It was concluded that the badger was the only species of wild mammal which was a reservoir of M. bovis in this area.

Avian Tuberculosis

A discussion of avain tuberculosis may conveniently be carried out under five heads. First, communicable nature of the disease; second, methods of dissemination; third, detection; fourth, post-mortem appearance of the tubercular bird; and fifth, control.Communicable Natureofthe Disease.When Robert Koch, in 1882, discovered the bacillus of tuberculosis, he established the fact that this organism was the sole direct cause of tuberculosis in mammals, and that no case of the disease could possibly occur unless the germs gained entrance to the body of the susceptible individual from an already existing case. Later researches showed that in this particular, tuberculosis in birds differs in nowise from the disease in man and the lower animals. Although poorly lighted or poorly ventilated houses, insufficient or unwholesome food, errors in breeding, the presence of mites, or any other condition which would tend to lower the normal vigor and vitality of the birds .