F Brossier1, N Veziris, V Jarlier, W Sougakoff. 1. National Reference Centre for Mycobacteria, Hôpital Pitié-Salpêtrière, AP-HP, Université Pierre et Marie Curie (UPMC), Université Paris 06, Faculté de Médecine Pitié-Salpêtrière, Paris, France.
Abstract
SETTING: We recently evaluated the Genotype MTBDR test for assessing Mycobacterium tuberculosis resistance to rifampicin (RMP) and isoniazid (INH) by detecting mutations in rpoB (codons 511-533) and katG (codon 315). A new version of the test, MTBDR plus, has been designed to also detect mutations in the regulatory region of inhA. OBJECTIVE: To evaluate the performance of MTBDR plus over MTBDR. RESULTS: In 113 isolates, MTBDR plus detected all 76 RMP-resistant (RMP-R) strains and all 64 INH-resistant (INH-R) strains with KatG-315 mutations, 59 of which displayed a high level of INH resistance. It also identified 18 strains undetectable by MTBDR, without mutation in KatG-315 but with a -15 C-->T mutation in the regulatory region of inhA, of which 15 displayed a low level of INH resistance. Thirteen INH-R strains, which mainly harboured mutations in KatG at positions other than 315, were undetected by MTBDR plus. CONCLUSION: MTBDR plus retains the accuracy shown by MTBDR in detecting RMP resistance and is more sensitive in detecting INH resistance (86% vs. 67%), particularly at low levels (minimum inhibitory concentration<1 mg/l, 69% vs. 17%). The negative predictive value of the test (the probability of a strain with a wild-type test being susceptible to INH) is >98% when the rate of INH is <10%, as it is in France.
SETTING: We recently evaluated the Genotype MTBDR test for assessing Mycobacterium tuberculosis resistance to rifampicin (RMP) and isoniazid (INH) by detecting mutations in rpoB (codons 511-533) and katG (codon 315). A new version of the test, MTBDR plus, has been designed to also detect mutations in the regulatory region of inhA. OBJECTIVE: To evaluate the performance of MTBDR plus over MTBDR. RESULTS: In 113 isolates, MTBDR plus detected all 76 RMP-resistant (RMP-R) strains and all 64 INH-resistant (INH-R) strains with KatG-315 mutations, 59 of which displayed a high level of INH resistance. It also identified 18 strains undetectable by MTBDR, without mutation in KatG-315 but with a -15 C-->T mutation in the regulatory region of inhA, of which 15 displayed a low level of INH resistance. Thirteen INH-R strains, which mainly harboured mutations in KatG at positions other than 315, were undetected by MTBDR plus. CONCLUSION: MTBDR plus retains the accuracy shown by MTBDR in detecting RMP resistance and is more sensitive in detecting INH resistance (86% vs. 67%), particularly at low levels (minimum inhibitory concentration<1 mg/l, 69% vs. 17%). The negative predictive value of the test (the probability of a strain with a wild-type test being susceptible to INH) is >98% when the rate of INH is <10%, as it is in France.
Authors: Anwar Sheed Khan; Muhammad Tahir Khan; Sajid Ali; Taj Ali Khan; Muhammad Qasim; Arif Malik; Sajid Ali; Wasim Sajjad; Qurrat Ul Ain; Muhammad Irfan Journal: Arch Microbiol Date: 2021-02-27 Impact factor: 2.552
Authors: Ameeta S Kalokhe; Majid Shafiq; James C Lee; Susan M Ray; Yun F Wang; Beverly Metchock; Albert M Anderson; Minh Ly T Nguyen Journal: Am J Med Sci Date: 2013-02 Impact factor: 2.378