Rapid Detection For Isoniazid And Rifampin Resistance In Mycobacterium Tuberculosis By Phage Amplified Biologically Assay

Objective:To evaluate the clinical value at the primary level laboratories of phage amplified biologically assay (PhaB) in the detection of isoniazid and rifampin resistance in Mycobacterium tuberculosis.Methods: Sixty-nine strains of Mycobacterium tuberculosis strains were obtained from the sputum of the primary pulmonary tuberculosis cases, without antituberculotic treatment and those who have been given antituberculotic treatment no more than one month. Ninety-eight strains were obtained from the sputum of the repeated pulmonary tuberculosis cases, with an abortive initial treatment, and sputum bacteriologically positive after a regular antituberculotic course, more than one month irregular antituberculotic treatment, and the chronic pulmonary tuberculosis patients showing bacteria-discharge. Ther total 167 strains were cultured on Lo-wenstein-Jensen culture medium and identified as Mycobacterium tuberculosis isolates. Isoniazid and rifampin resistance in Mycobacterium tuberculosis were detected by the PhaB assay and the conventional proportion method, and the results of both methods were compared to each other.in sensitivity ,specificity and accuracy.Results: In 69 Mycobacterium tuberculosis isolates from primary pulmonary tuberculosis cases, 10 strains were found to be isoniazid resistant (10/69) and 59 to be isoniazid sensitive (59/69) by the PhaB assay but 5 strains were found to be isoniazid resistant (5/69) and 64 to be isoniazid sensitive (64/69) by the conventional proportion method. In comparison with the results of the conventional proportion method, the sensitivity, specificity and accuracy of the PhaB assay on isoniazid were 80% (4/5), 90.6% (58/64) and 89.9% (62/69), respectively. Also in 69 Mycobacterium tuberculosis isolates from primary pulmonary tuberculosis cases, 6 strains were found to be rifampin resistant (6/69) and 63 to be rifampin sensitive (63/69) by the PhaB assay, but 3 strains were found to be rifampin resistant (3/69) and 66 to be rifampin sensitive (66/69)by the conventional proportion method. In comparison with the results of the conventional proportion method, the sensitivity, specificity and accuracy of the PhaB assay on rifampin were 100% (3/3), 95.5% (63/66) and 95.7% (66/69), respectively. Otherwise, in 98 Mycobacterium tuberculosis isolates from repeated pulmonary tuberculosis cases, 42 strains were found to be isoniazid resistant (42/98) and 56 to be isoniazid sensitive (56/98) by the PhaB assay, but 39 strains were found to be isoniazid resistant (39/98) and 59 to be isoniazid sensitive (59/98) by the conventional proportion method. compared with the results of the conventional proportion method, the sensitivity, specificity and accuracy of the PhaB assay on isoniazid were 89.7%(35/39), 88.1% (52/59) and 88.7% (87/98),respectively. Also in 98 Mycobacterium tuberculosis isolates from repeated pulmonary tuberculosis cases, 38 strains were found to be rifampin resistant (38/98) and 60 to be rifampin sensitive (60/98) by the PhaB assay, but 35 strains were found to be rifampin resistant (35/98) and 63 to be rifampin sensitive (63/98) by the conventional proportion method. In comparison with the results of the conventional proportion method, the sensitivity, specificity and accuracy of the PhaB assay on rifampin were 97.1% (34/35), 93.7% (59/63) and 94.9% (93/98), respectively.Conclusion: The conventional proportion method can not meet the needs of the rapid drug susceptibility test because it can not get results until four weeks, However, the PhaB assay has much higher sensitivity, specificity and accuracy in drug susceptibility test than the conventional proportion method, and the susceptibility results of the PhaB assay can be early obtained only in 48～72h after a caltivation in 37℃. The PhaB assay is a rapid and accurate method in the detection of isoniazid and rifampin resistance in Mycobacterium tuberculosis. This method, which is simple to perform and does not need special equipment, is a prospective technology in the clinical laboratories at the primary level.