Tóm tắt

Background: Tuberculosis (TB) still threatens human beings when drug-resistant tuberculosis (DR-TB), such as rifampicin-resistant TB, isoniazid-resistant TB, multidrug-resistant TB (MDR-TB), pre-extensively drug-resistant TB, and extensively drug-resistant TB increases continuously. The drug susceptibility testing (DST) is important to detect DR-TB for TB treatment.

Objectives: The study aimed to assess first-line line probe assay (FL-LPA) performance of screening MDR-TB and detecting DR-TB on phenotypic drug susceptibility testing.

Materials and methods: A laboratory-based study was performed at Cho Ray Hospital from August 2023 to August 2024. The sputum samples of presumptive TB were inoculated in Mycobacterium growth indicator tube (MGIT). Positive inoculum was examined in acid-fast bacilli (AFB) by Ziehl-Neelsen microscope. Cord-forming AFB were yielded to FL-LPA to identify Mycobacterium tuberculosis complex (MTBC); detect rifampicin-resistant TB, isoniazid-resistant TB, and MDR-TB. The identified MTBC was subjected to FL phenotypic DST (performed by BACTEC MGIT 960) with SIRE kit, considering gold standard to assess FL-LPA performance. The detected multidrug and/or rifampicin-resistant TB (MDR/RR-TB) were subjected to the second- line MGIT DST including ethionamide, amikacin, levofloxacin, and linezolid to screen pre-extensively drug-resistant TB and extensively drug-resistant TB.

Results: Among 1853 samples inoculated, 621 positive MGIT tubes seen cord-forming AFB on Ziehl-Neelsen smear were performed to FL-LPA. Out of 621 LPA tests, 304 MTBC (61 isoniazid-resistant TB, 20 rifampicin-resistant TB, and 243 susceptible TB) were detected and compared to FL phenotypic DST. The excellent agreements between FL-LPA and FL phenotypic DST for detecting rifampicin-resistant TB, isoniazid- resistant TB, and MDR-TB were greater than 98%; kappa at 0.89 and above (p<0.001); with sensitivity values at 88.9% and above; specificity values at greater than 99%. For FL-MGIT DST, 101 (33.2%) were drug-resistant to at least one anti-TB agent, 81 (26.6%) to streptomycin, 60 (19.7%) to isoniazid, 20 (6.6%) to rifampicin. Among 20 MDR/RR-TB (2 rifampicin mono-resistant-TB and 18 MDR-TB) performed second line phenotypic DST, 25% resistance to ethionamide, and 100% susceptibility to amikacin, levofloxacin, and linezolid.

Conclusion:The performance of FL-LPA to detect rifampicin-resistant TB, isoniazid- resistant TB, and MDR-TB agreed perfectly with phenotypic DST. The reaffirmed critical concentration of isoniazid, rifampicin and levofloxacin would be used to screen DR-TB on population.