Abstract:

Objective To evaluate the detection and application value of BACTEC MGIT 960 mycobacterial liquid culture (referred to as “MGIT 960 culture”), GeneXpert MTB/RIF (GeneXpert) and fluorescent PCR melting curve analysis in smear-positive pulmonary tuberculosis (PTB) patients.Methods We retrospective analysized of total 411 smear-positive patients who were admitted to Shenyang Chest Hospital from Oct. 2016 to Feb. 2018. Through Mycobacterium tuberculosis antigen detection (MPB64 test) and met the clinical diagnostic criteria, 392 patients were diagnosed with tuberculosis, 19 patients with negative MPB64 and identified as non-tuberculous mycobacteria by gene chip strain. The detection efficiency of MGIT 960 culture, GeneXpert and fluorescent PCR melting curve technique in smear-positive PTB patients was compared. Based on the proportional drug sensitivity test, the detection efficiencies of drug resistance phenotypes and drug resistance genes were compared.Results In clinical confirmed 392 smear-positive PTB patients, the sensitivity of MGIT 960 culture, GeneXpert and fluorescent PCR melting curve technique to sputum samples were 96.17% (377/392), 99.74% (391/392) and 92.09% (361/392), respectively; the specificity were all 100.00% (19/19). Based on the proportional drug sensitivity test, the sensitivity of GeneXpert and PCR melting curve technique in RFP resistance test were both 94.44% (119/126). The sensitivity of PCR melting curve technique in INH, Lfx, Am resistance tests were 74.84% (116/155), 83.33% (75/90) and 44.00% (22/50). The sensitivity of MGIT 960 culture to RFP, INH, Lfx and Am resistance tests were 96.03% (121/126),98.06% (152/155), 100.00% (50/50) and 96.67% (87/90).Conclusion The GeneXpert method is easy, fast and safe, and can quickly diagnose tuberculosis and detect RFP resistance. Fluorescence PCR melting curve technology can detect four kinds drug resistance, with short detection time, rapid diagnosis of multidrug resistant tuberculosis/extensive drug-resistant tuberculosis, and guiding clinical medication. The MGIT 960 liquid susceptibility is extremely consistent with modified Roche culture technology. It is a common method for rapid diagnosis of tuberculosis and first-line drug-resistant tuberculosis which can significantly shorten the time of phenotypic drug susceptibility test.

Key words: Tuberculosis, pulmonary, Drug resistant, bacterial, Polymerase chain reaction techniques, Clinical laboratory technology, Comparative study