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Updated: Apr 27, 2026

An Automated Culture System for Use in Preclinical Testing of Host-Directed Therapies for Tuberculosis
Published on: August 16, 2021
[Macrolide and linezolid susceptibility testing for Mycobacterium intracellulare isolates]
Hongfei Duan1, Qian Liang1, Naihui Chu1
1Department of Tuberculosis, Beijing Tuberculosis & Thoracic Tumor Research Institute, Beijing Chest Hospital affiliated to Capital Medical University, Beijing 101149, China.
Objective:
To investigate the susceptibility of Mycobacterium intracellulare isolates to clarithromycin, azithromycin and linezolid, and therefore to explore the possibility of using these drugs to treat Mycobacterium intracellulare diseases.
Methods:
The minimal inhibitory concentrations (MICs) of the 3 antibiotics against 76 Mycobacterium intracellulare isolates were determined by using microplate alamar blue assay (MABA).
Results:
The MIC90 of clarithromycin against Mycobacterium intracellulare isolates was 2 mg/L. The proportion of susceptible, intermediate and resistant isolates to clarithromycin was 93.4% (71/76), 0.0% (0/76) and 6.6% (5/76), respectively. The MIC90 of azithromycin against the isolates was 32 mg/L. The proportion of susceptible, intermediate and resistant isolates to azithromycin was 94.7% (72/76), 0.0% (0/76) and 5.3% (4/76), respectively. The MIC90 of linezolid was 64 mg/L. The proportion of susceptible, intermediate and resistant isolates to linezolid was 32.9% (25/76), 22.4% (17/76) and 44.7% (34/76), respectively. Among the 5 isolates resistant to clarithromycin, 4 were resistant to azithromycin, and 2 were resistant to linezolid.
Conclusions:
Most of the Mycobacterium intracellulare isolates were sensitive to clarithromycin. High cross-resistance between clarithromycin and azithromycin was present, but some clarithromycin-resistant isolates were sensitive to linezolid.
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