Differences in skin test reactions to official and defined antigens in guinea pigs exposed to non-tuberculous and tuberculous bacteria

Abstract

The single and comparative intradermal tuberculin tests (SITT and CITT) are official in vivo tests for bovine tuberculosis (TB) diagnosis using bovine and avian purified protein derivatives (PPD-B and PPD-A). Infection with bacteria other than Mycobacterium tuberculosis complex (MTC) can result in nonspecific reactions to these tests. We evaluated the performance of the skin test with PPDs and new defined antigens in the guinea pig model. A standard dose (SD) of Rhodococcus equi, Nocardia sp., M. nonchromogenicum, M. monacense, M. intracellulare, M. avium subsp. paratuberculosis, M. avium subsp. avium, M. avium subsp. hominissuis, M. scrofulaceum, M. persicum, M. microti, M. caprae and M. bovis, and a higher dose (HD) of M. nonchromogenicum, M. monacense, M. intracellulare, M. avium subsp. paratuberculosis were tested using PPD-B, PPD-A, P22, ESAT-6-CFP-10-Rv3615c peptide cocktail long (PCL) and fusion protein (FP). The SD of R. equi, Nocardia sp., M. nonchromogenicum, M. monacense, M. intracellulare and M. avium subsp. paratuberculosis did not cause any reactions. The HD of M. nonchromogenicum, M. monacense, M. intracellulare, and M. avium subsp. paratuberculosis and the SD of M. avium subsp. hominissuis, M. scrofulaceum and M. persicum, caused nonspecific reactions (SIT). A CITT interpretation would have considered M. avium complex and M. scrofulaceum groups negative, but not all individuals from M. nonchromogenicum HD, M. monacense HD and M. persicum SD groups. Only animals exposed to M. bovis and M. caprae reacted to PCL and FP. These results support the advantage of complementing or replacing PPD-B to improve specificity without losing sensitivity.

Detection of Mycobacterium bovis in nasal swabs from communal goats (Capra hircus) in rural KwaZulu-Natal, South Africa

“…This was likely why there was a high percentage (43%; 53/123) of positive cultures that contained matching mycobacterial species in both the culture isolate and DNA extracted directly from swabs. The observed diversity of NTMs identified suggests that these goats were exposed to environmental mycobacteria, many of which have been recently proven to confound M. bovis diagnosis in guinea pigs, especially when using tests based on host immune responses ( Fernández-Veiga et al, 2023 ). Further studies are needed to investigate the association between presence of NTMs and potential cross-reactivity in M. bovis specific cell-mediated immunological tests in goats.…”

Detection of non-tuberculous mycobacteria in native wildlife species at conservation risk of Argentina

“…paratuberculosis and M. avium subsp. hominissuis , within others, could make animals react to the SITT ( 44 ). In Argentina, a study conducted by Oriani et al ( 12 ), in which cattle were inoculated with NTM isolated from soils and wetlands, this NTM included M. kansasii, M. nonchromogenicum, M. gordonae, M. arupense, M. phlei, M. fortuitum and M. peregrinum , and showed that they may cause unspecific reactions, but that these reactions are not maintained over time ( 12 ).…”

Specific identification of Mycobacterium bovis by Loop-Mediated Isothermal Amplification (LAMP) targeting the Region of Difference 12 (RD12) of the M. tuberculosis complex

“…TST relies on in vivo delayed-type hypersensitivity test that reveals infections 3 to 8 weeks after contact with M. bovis , so it is not possible to distinguish between active and latent infections. Moreover, TST has low specificity because of cross-reactive responses due to the sharing of many antigens between tuberculous and nontuberculous mycobacteria [32] . On the other hand, even though M. bovis culture is considered the gold standard for BTB diagnosis, it is time-consuming and requires specialized equipment and trained staff.…”