ABSTRACT
Objective:To observe the characteristics of the phagocytosis and bactericidal function of multidrug-resistant Mycobacterium tuberculosis(MDR- Mtb)-infected macrophage model, and the changes of the immune response and metabolic function in the process of phagocytosis and bactericidal function, aiming to provide reference for studying the role and mechanism of macrophages in the occurrence and development of multidrug-resistant tuberculosis(MDR-TB). Methods:We established MDR- Mtb and H37Rv-infected macrophage models, and used the colony-forming unit (CFU), Magnetic Luminex ? Assay and Cholesterol Assay kit to observe the effects on phagocytosis and bactericidal function, the secretion of Th1(IL-12/23 p40, IL-27 and TNF-α) and Th2 cytokines (IL-6 and IL-10) and cholesterol metabolism. The data were analyzed by SPSS25.0 software. The data were expressed as Mean± SD and analyzed by t test or F test. P<0.05 was considered statistically significant. Results:(1) After MDR- Mtb-infected macrophages, the intracellular CFU gradually increased and reached the highest at 24 h, while the extracellular CFU gradually decreased and reached the lowest at 24 h. The intracellular CFU at 48 h was lower than that at 24 h, while the extracellular CFU was higher than that at 24 h ( P<0.05). Both intracellular and extracellular CFU at 48 h were close to those at 4 h ( P>0.05). The intracellular CFU was lower than the H37Rv group at 8-48 h, while the extracellular CFU was higher than the H37Rv group ( P<0.05). (2) The level of IL-12/23 p40, IL-27, TNF-α, IL-6 and IL-10 of MDR-TB group were higher than those of blank group ( P<0.05), but the level of TNF-α and IL-6 at 24 h and 48 h were higher than that at 4 h ( P<0.05). IL-12/23 p40 and TNF-α at 48 h and IL-6 at 24 h were lower than those of the H37Rv group, while IL-27 at 48 h was higher than that of the H37Rv group ( P<0.05). (3) The levels of cholesterol of MDR-TB group at 24 h and 48 h were lower than those of 4 h and blank group ( P<0.05), but the level of cholesterol was similar to the H37Rv group at any time ( P>0.05). (4) TNF-α reached the highest when the intracellular CFU reached the highest at 24 h, and IL-6 reached the highest when the intracellular CFU decreased at 48 h. With the decreasing of cholesterol expression, the intracellular CFU increased and then decreased. Conclusions:MDR- Mtb could induce the phagocytosis and bactericidal function of macrophages, increase the expression of Th1 and Th2 cytokines and promote the utilization and consumption of cholesterol, but this function was weaker than that of H37Rv strain.
ABSTRACT
BACKGROUND: Because of the long time required for conventional drug susceptibility test (DST) for rifampin and isoniazid, development of rapid DSTs is necessary. Recently, the AdvanSure(TM) MDR-TB GenoBlot Assay kit (LG Life Science, Korea), using reverse hybridization line blot assay, was developed. We compared this kit with Genotype(R) MTBDRplus (HAIN Lifescience, Germany) and conventional DST. METHODS: Of the DNAs preserved after performing DST by using Genotype(R), we selected 144 samples having conventional DST results. The experiments with both the kits were performed according to the manufacturers' instructions. For the samples for which discrepant results were obtained, sequencing was performed if the DNA was available. Conventional DST was performed at the Korean Institute of Tuberculosis by using the absolute concentration method. RESULTS: For rifampin, the findings obtained using both the kits were the same with concordance rates of 98.6% (142/144) compared to conventional DST. Of the 2 discrepant findings, one was very major error and the other was major error. For isoniazid, compared to conventional DST, concordance rates of AdvanSure(TM) and Genotype(R) were 95.8%(138/144) and 95.1%(137/144) respectively. Of the 6 discrepant findings between conventional method and Advansure(TM), 5 were very major error and one was major error. All the 7 discrepant findings between conventional method and Genotype(R) were very major error. CONCLUSIONS: The findings obtained using AdvanSure(TM) showed high concordance with those obtained using Genotype(R) and conventional DST. This kit has a higher rate of detection of isoniazid resistance because it includes probes for an additional target (ahpC).