15 research outputs found

    'Emerging' mycobacteria in South Africa

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    Disease can be caused by various species of the genus Mycobacterium. A number of reports, both published and unpublished, of rarely reported mycobacteria have surfaced in South Africa in the last few years. Some unusual hosts have also been involved, causing concern in some quarters.These include reports on Mycobacterium goodii in a spotted hyaena (Crocuta crocuta), M. xenopi in a ruffed lemur (Varecia variegata), M. intracellulare in wild-caught chacma baboons (Papio ursinus), the 'dassie bacillus' in free ranging rock hyrax (dassies; Procavia capensis) the 'oryx bacillus' from free-ranging buffalo (Syncerus caffer) and M. tuberculosis in suricates (Suricata suricatta), a domestic dog and in baboons. In this article it has been attempted to put these in context and show how improved surveillance and technologies have allowed mycobacteria to be identified to species level more easily. Most of the unusual mycobacterial species have most likely been present in the region for many years and have probably caused disease episodes before, but have been misdiagnosed. Each case must be evaluated carefully with respect to the animal species involved, the environment in which the host is found and the mycobacterial species, and operational decisions made accordingly.Revie

    Detection of Mycobacterium tuberculosis infection in dogs in a high-risk setting

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    Dogs infected with Mycobacterium tuberculosis can develop clinical tuberculosis (TB) but there are currently no validated immunological assays for diagnosing this infection in this species. Using a post mortem survey we investigated the prevalence of non-clinical M. tuberculosis infection and clinical TB disease in a high-risk population of dogs and developed and utilised a novel interferon-gamma release assay to determine the risk of transmission of M. tuberculosis from TB patients to contact dogs. The prevalence of clinical TB in dogs from a high-risk setting was 1% (95% CI: 0-5%) while the prevalence of immunological sensitization to M. tuberculosis antigens in dogs living in contact with sputum smear-positive TB patients was 50%. The IGRA proved a useful test of M. tuberculosis infection in dogs and the high levels of transmission of this pathogen from humans to companion dogs should be considered when assessing the zoonotic risks associated with such animals. © 2011 Elsevier Ltd. All rights reserved.Articl

    Detection of Mycobacterium tuberculosis infection in dogs in a high-risk setting

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    Immunogenetics and cellular immunology of bacterial infectious disease

    Mycobacterium tuberculosis Beijing genotype: A template for success

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    Please help us populate SUNScholar with the post print version of this article. It can be e-mailed to: [email protected]

    Tuberculosis recurrence: Exogenous or endogenous?

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    With the advent of molecular epidemiology, perhaps the most significant finding has been that a recurrent episode of tuberculosis (TB) can occur by exogenous reinfection. This raises several questions: Does prior infection confer protective immunity? Do mixed infections occur, and does exogenous reinfection play a significant role in high-incidence settings, where individuals could be exposed to multiple infecting doses during their lifetime? Combining data from the literature with a simple mathematical model we illustrate that while disease due to exogenous reinfection after cure constitutes a significant proportion of recurrent TB, it represents a very small portion of the total number of TB cases. Although the true contribution of exogenous reinfection cannot be quantified, its association with recurrence serves as a barometer of its contribution to disease progression in previously untreated individuals. One of the most important functions of any new antituberculosis drug is the ability to prevent endogenous reactivation of disease. Molecular epidemiology now enables us to differentiate endogenous reactivation and exogenous reinfection. In this paper we discuss the clinical relevance of exogenous reinfection, questions surrounding its role in TB disease and its importance in the accurate evaluation of new drugs. Copyright © 2011 S. Karger AG, Basel.Articl

    Modification of the QuantiFERON-TB Gold (In-Tube) assay for the diagnosis of Mycobacterium bovis infection in African buffaloes (Syncerus caffer)

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    African buffaloes (Syncerus caffer) are the most significant wildlife maintenance hosts of Mycobacterium bovis, the causative organism of bovine tuberculosis (BTB). Current diagnostic tests for the detection of M. bovis infection in free-ranging buffaloes have numerous limitations and we wished to evaluate a modification to a human TB assay, the QuantiFERON-TB Gold (In-Tube) assay (QFT), as a practical diagnostic test for BTB in buffaloes. One hundred and seventy-five buffaloes were tested using the single intradermal comparative tuberculin test (SICTT) and a modified QFT (mQFT). An appropriate cut-off point for the mQFT was derived from SICTT results using receiver operator characteristic curve analysis. Twenty-six SICTT-positive buffaloes were killed and subjected to necropsy, and selected tissues were processed for mycobacterial culture and speciation. An optimal cut-off point for the mQFT was calculated as 66. pg/ml. The assay correctly detected 39/40 SICTT-positive buffaloes and 129/134 TST-negative buffaloes and M. bovis was cultured from 21/26 slaughtered SICTT/mQFT-positive animals. The mQFT shows promise as a practical test for M. bovis infection in buffaloes and shows a sensitivity and specificity at least similar to that of the TST. © 2011 Elsevier B.V.Articl

    Rifampicin reduces susceptibility to ofloxacin in rifampicin-resistant Mycobacterium tuberculosis through efflux

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    Rationale: Central dogma suggests that rifampicin resistance in Mycobacterium tuberculosis develops solely through rpoB gene mutations. Objective: To determine whether rifampicin induces efflux pumps activation in rifampicin resistant M. tuberculosis strains thereby defining rifampicin resistance levels and reducing ofloxacin susceptibility. Methods: Rifampicin and/or ofloxacin minimum inhibitory concentrations (MICs) were determined in rifampicin resistant strains by culture in BACTEC 12B medium. Verapamil and reserpine were included to determine their effect on rifampicin and ofloxacin susceptibility. RT-qPCR was applied to assess expression of efflux pump/ transporter genes after rifampicin exposure. To determine whether verapamil could restore susceptibility to first-line drugs, BALB/cmice were infected with aMDR-TB strain and treated with first-line drugs with/without verapamil. Measurements and Main Findings: Rifampicin MICs varied independently of rpoB mutation and genetic background. Addition reserpine and verapamil significantly restored rifampicin susceptibility (p = 0.0000). RT-qPCR demonstrated that rifampicin induced differential expression of efflux/transporter genes in MDR-TB isolates. Incubation of rifampicin mono-resistant strains in rifampicin (2 mg/ml) for 7 days induced ofloxacin resistance (MIC > 2 μg/ml) in strains with an rpoB531 mutation. Ofloxacin susceptibility was restored by exposure to efflux pump inhibitors. Studies in BALB/c mice showed that verapamil in combination with first-line drugs significantly reduced pulmonary CFUs after 1 and 2 months treatment (p < 0.05). Conclusion: Exposure of rifampicin resistant M. tuberculosis strains to rifampicin can potentially compromise the efficacy of the secondline treatment regimens containing ofloxacin, thereby emphasising the need for rapid diagnostics to guide treatment. Efflux pump inhibitors have the potential to improve the efficacy of antituberculosis drug treatment.Articl

    Differentiation of Mycobacterium tuberculosis complex by PCR amplification of genomic regions of difference

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    Differentiation of members of the Mycobacterium tuberculosis complex by conventional mycobacteriological methods is time consuming, making surveillance of species-specific disease difficult. A two-step, multiplex polymerase chain reaction (PCR) method based on genomic regions of difference (RD1, RD1 mic, RD2seal, RD4, RD9 and RD12) was developed for the differentiation of M. canettii, M. tuberculosis, M. africanum, M. microti, M. pinnipedii, M. caprae, M. bovis and M. bovis BCG. The size of the respective multiplex PCR amplification products corresponded to the presence of the different M. tuberculosis complex members. This method allows for rapid differentiation, making it suitable for routine laboratories and surveillance purposes. © 2006 The Union.Articl

    Differentiation of Mycobacterium tuberculosis complex by PCR amplification of genomic regions of difference

    No full text
    Differentiation of members of the Mycobacterium tuberculosis complex by conventional mycobacteriological methods is time consuming, making surveillance of species-specific disease difficult. A two-step, multiplex polymerase chain reaction (PCR) method based on genomic regions of difference (RD1, RD1 mic, RD2seal, RD4, RD9 and RD12) was developed for the differentiation of M. canettii, M. tuberculosis, M. africanum, M. microti, M. pinnipedii, M. caprae, M. bovis and M. bovis BCG. The size of the respective multiplex PCR amplification products corresponded to the presence of the different M. tuberculosis complex members. This method allows for rapid differentiation, making it suitable for routine laboratories and surveillance purposes. © 2006 The Union.Articl
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