Evaluation of integral membrane antigens of Mycobacterium habana for serodiagnosis of extrapulmonary tuberculosis: association between levels of antibodies and Mycobacterium tuberculosis antigens

The performance of integral membrane antigens (IMAs) of Mycobacterium habana TMC 5135 in detecting antimycobacterial antibodies in serum and body fluids of patients mainly of extrapulmonary tuberculosis was evaluated. The IMAs were recovered from the detergent phase during Triton X‐114 treatment of the plasma membrane of M. habana . Antimycobacterial antibodies were detected by ELISA using IMAs in serum and body fluids of 42 patients and 62 control subjects. As authentic adjunct Mycobacterium tuberculosis antigens were also detected (by ELISA) in body fluids and circulating immune complexes using anti‐ M. tuberculosis H 37 Ra antibodies. Anti‐ M. habana IMA antibody detection increased the positivity rate from 26.% (11/42) and 10% (4/42) obtained by culture and smear microscopy, respectively, to 86% (36/42). M. tuberculosis antigens were also found in 29 out of 36 anti‐ M. habana IMA antibody‐positive cases. Interestingly, all 11 culture‐positive cases were also positive for anti‐ M. habana IMA antibodies. The mean antigen titres in 23 cases, positive for antigens in body fluids, were 2.34 times higher in those who were also positive for anti‐IMA antibodies in serum than in those negative for these antibodies. M. habana IMAs may be promising non‐tubercular candidate antigens in ELISA‐based serodiagnosis of extrapulmonary tuberculosis with substantial sensitivity, specificity and safety.