No abstract

Tuberculosis is emerging as a major public health problem in developing and developed wodd. Early and precise diagnosis is of prime importance in successful control of Infection. Indirect ELISA with penicillinase as marker was developed using purified M. tuberculosis excretory-secretory (EST-DEt) antigen for detecting IgG antibodies in pulmonary tuberculosis. The assay System gave a overall sensitivity of 82% for both smear positive and smear negative pulmonary tuberculosis cases with a specificity of 84%. The positive and negative predictive values were 75% and 88% respectivaly. Further studies with EST-DE t antigen revealed that, it contains two of the active antigen fractions of Mtb EST antigen i.e. Mtb and Mtb , as demonstrated by inhibition ELISA. Reactivity with monoclonal antibodies HGT 3a showed the presence of 38 KDa molecule in EST-DE 1 antigen.

Trichloroacetic acid (TCA) solubilized and DEAE fractionated Mycobacterium tuberculosis H37Ra excretory-secretory (ES) antigen viz., Mtb EST DE1 and affinity purified goat antibodies to the TCA solubilized ES antigen (Mtb EST) were explored in detecting tubercular antibody and antigen respectively in sera of bone and joint tuberculosis by indirect and sandwich ELISA. Out of total 36 bone & joint tuberculosis cases, tubercular antibody was detected by indirect ELISA in 30 patients (sensitivity 83%), while circulating tubercular antigen was detected by sandwich EL;SA in 27 patients (sensitivity 75%). Out of 34 non tubercular disease control cases, 10 patients showed positive reaction for antibody while only 4 patients showed positive reaction for antigen. In another group of 34 healthy subjects who were screened, 4 individuals showed positive reaction for tubercular antibody and 2 cases for antigen. This study shows that antigen detection assay using affinity purified anti Mtb EST antigen antibody is superior with overall specificity of 91% as compared to antibody detection assay with 75% specificity in bone & joint tuberculosis.

The diagnostic potential for detection of IgG to Mycobacterium tuberculosis excretory secretory (ES) antigen in childhood pulmonary and extrapulmonary tuberculosis was explored. IgG antibody to M. tuberculosis ES antigen was detected by indirect penicillinase ELISA. Twenty (80%) out of 25 pulmonary tuberculosis cases (clinically diagnosed and/or AFB-positive), five of nine tuberculous pleural effusion cases and only six of 69 cases in the control group were positive for IgG antibody to M. tuberculosis ES antigen. All CSF and sera were positive for IgG antibody in 12 cases of clinically diagnosed tuberculous meningitis (TBM). Out of 35 cases in the control group for TBM, all five cases of pyogenic meningitis but none of the 13 cases of viral encephalitis, five cases of enteric encephalopathy and 12 cases with no CNS infection were positive for anti-tubercular IgG antibody in CSF samples. Only two of them, i.e. one case of pyogenic meningitis and the other with no CNS infection, were positive for antibody in sera. The study demonstrated the potential of this assay in the diagnosis of tuberculosis in children where bacteriological confirmation is very difficult.