Abstract
In South Africa, mycobacterial culture is regarded as the gold standard for the detection of Mycobacterium tuberculosis complex (MTBC) infection in wildlife even though it is regarded as “imperfect.” We compared a novel decontamination and mycobacterial culture technique (TiKa) to the conventional mycobacterium growth indicator tube (MGIT) system using known amounts of bacilli and clinical samples from MTBC-infected African buffaloes (Syncerus caffer), white rhinoceros (Ceratotherium simum), and African elephants (Loxodonta africana). Use of the TiKa-KiC decontamination agent on samples spiked with 10,000 to 10 colony forming units (cfu) of M. bovis (SB0121) and M. tuberculosis (H37Rv) had no effect on isolate recovery in culture. In contrast, decontamination with MGIT MycoPrep resulted in no growth of M. bovis samples at concentrations < 1,000 cfu and M. tuberculosis samples < 100 cfu. Subsequently, we used the TiKa system with stored clinical samples (various lymphatic tissues) collected from wildlife and paucibacillary bronchoalveolar lavage fluid, trunk washes, and endotracheal tube washes from 3 species with known MTBC infections. Overall, MTBC recovery by culture was improved significantly (p < 0.01) by using TiKa compared to conventional MGIT, with 54 of 57 positive specimens versus 25 of 57 positive specimens, respectively. The TiKa mycobacterial growth system appears to significantly enhance the recovery of MTBC members from tissue and paucibacillary respiratory samples collected from African buffaloes, African elephants, and white rhinoceros. Moreover, the TiKa system may improve success of MTBC culture from various sample types previously deemed unculturable from other species.
Highlights
Bovine tuberculosis is caused by infection with Mycobacterium bovis; human tuberculosis (TB) is caused primarily by M. tuberculosis; both species are members of the M. tuberculosis complex (MTBC).[14]
We further describe here the use of the TiKa system for the detection of M. tuberculosis and M. bovis from stored clinical tissue and paucibacillary respiratory tract samples from 3 wildlife species with known MTBC infection status
After decontaminating serial dilutions of M. bovis (SB0121) and M. tuberculosis (H37Rv) cultures with TiKa KiC, M. bovis and M. tuberculosis were successfully cultured from all dilutions from 10,000 to as low as 10 cfu (Fig. 1A, 1B)
Summary
Bovine tuberculosis (bTB) is caused by infection with Mycobacterium bovis; human tuberculosis (TB) is caused primarily by M. tuberculosis; both species are members of the M. tuberculosis complex (MTBC).[14]. There is still a paucity of detection tests and disease surveillance programs for wildlife, and MTBC infections can remain undetected for years, resulting in uncontrolled spread.[4,10] In cattle and buffaloes, the conventional antemortem diagnosis of bTB is based on the measurement of antigen-specific cell-mediated immune (CMI) responses, and the definitive diagnosis is based on detection of bacilli by mycobacterial culture.[9,15] species-specific in vitro assays for detection of CMI responses to MTBC are either very limited, as in the case of African rhinoceros,[4] or do not yet exist, as for African elephants. We further describe here the use of the TiKa system for the detection of M. tuberculosis and M. bovis from stored clinical tissue and paucibacillary respiratory tract samples from 3 wildlife species with known MTBC infection status
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