Abstract:

Objective: To evaluate the effectiveness of the BS-400 Automatic Mycobacterium Liquid Culture System (BS-400 Culture System) in cultivating Mycobacterium in clinical specimens. Methods: A total of 427 specimens of suspected tuberculosis patients who visited Hangzhou Thoracic Hospital Affiliated to Zhejiang University School of Medicine from March to May 2022 were collected. The specimens included 331 respiratory tract specimens (including sputum and respiratory lavage fluid) and 96 non-respiratory tract specimens (including cerebrospinal fluid, tissues, secretions, urine, bone marrow, necrosis, etc.), except blood and feces. All specimens were simultaneously cultured using the BACTEC MGIT 960 liquid culture system (MGIT 960 culture system) and the BS-400 culture system. Bacterial isolation and species identification would be carried out on samples with positive culture results. The differences in the positive rate, detection time, contamination rate, and cost of two culture systems for different types of Mycobacterium specimens were compared, and the detection efficiency of the BS-400 culture system for Mycobacterium infections in different types of specimens was evaluated using the culture results of the MGIT 960 culture system as a reference standard. Results: The positive rate of BS-400 culture system for respiratory tract specimens was 32.02% (106/331), and the contamination rate was 5.14% (17/331); the positive rate of culture for non-respiratory tract specimens was 17.70% (17/96), and the contamination rate was 1.04% (1/96), compared with those of MGIT 960 culture system (32.93% (109/331) and 5.44% (18/331), 15.63% (15/96) and 2.08% (2/96), respectively), the difference was not statistically significant (χ² values were 0.062, 0.030, 0.150, and 0.339, P values were 0.803, 0.862, 0.699, and 1.000, respectively). The detection time was 12.31 (7.89, 19.56) days of the BS-400 culture system, and was 9.79 (7.00, 16.58) days of the MGIT 960 culture system, with no statistically significant difference (Z=-1.895, P=0.058). Using the culture results of MGIT 960 culture system as a reference standard, the sensitivity and specificity of BS-400 culture system for detecting Mycobacterium infection specimens in respiratory tract were 93.58% (102/109) and 98.20% (218/222), and the Kappa value was 0.924; the sensitivity and specificity for detecting Mycobacterium infection specimens in non-respiratory tract were 100.00% (15/15) and 97.53% (79/81), and the Kappa value was 0.925. The testing cost of the BS-400 culture system (RMB (55±10) yuan per specimen) was approximately 70% of that of the MGIT 960 culture system (RMB (75±10) yuan per specimen). Conclusion: BS-400 culture system has high detection efficiency for Mycobacterium in clinical samples of suspected tuberculosis patients, and has good application value.

Key words: Mycobacterium, Infection, Culture techniques, Evaluation studies