Research and Educational Professional Center for Genetic and Laboratory Technologies, Samara State Medical University, Samara, Russia.
Research and Educational Professional Center for Genetic and Laboratory Technologies; Department of Fundamental and Clinical Biochemistry with Laboratory Diagnostics, Samara State Medical University, Samara, Russia.
Int J Mycobacteriol. 2023 Apr-Jun;12(2):157-161. doi: 10.4103/ijmy.ijmy_85_23.
Problem with mass spectrometers is the difficulty in identifying some genera of acid-fast bacteria (AFB). Due to the peculiarities of the colony architectonics (the formation of dry colonies with a complex structure) and the structure of the cell wall, the probability of obtaining a sufficient amount of ribosomal proteins is significantly reduced. This problem is partially solved using an extended method of direct application and extraction with formic acid, which can significantly improve the quality of the identification.
The study analyzed strains of microorganisms obtained during the examination of patients with suspected tuberculosis. In total, 287 strains of nontuberculous mycobacteria (NTM) were obtained. In addition, 63 strains of the most common bacteria from the AFB group were analyzed. Matrix-assisted laser desorption/ionization (MALDI) was used. Three main methods of sample preparation of microorganisms according to the manufacturer's recommendations for use with the MALDI-time-of-flight (ToF) mass spectrometry method were used in the work: Direct coating method, extended direct coating method, and formic acid extraction method.
When evaluating the influence of the cultivation medium on the result of NTM identification by MALDI-ToF mass spectrometry, statistically significant results of the influence of the medium on the result of NTM identification were revealed for all compared parameters.
Optimization of sample preparation protocols and assessment of the impact on the identification of new methods of cultivating microorganisms can significantly improve the quality of the identification of both clinically significant microorganisms from the AFB group and saprophytic microflora, the clinical significance of which has not been proven at the moment.
质谱仪的问题在于难以识别一些抗酸杆菌（AFB）属。由于菌落结构（形成具有复杂结构的干燥菌落）和细胞壁结构的特殊性，获得足够量核糖体蛋白的概率大大降低。通过使用扩展的直接应用和甲酸提取方法，可以部分解决这个问题，这可以显著提高鉴定质量。
该研究分析了在疑似结核病患者检查中获得的微生物菌株。总共获得了 287 株非结核分枝杆菌（NTM）。此外，还分析了 AFB 组中最常见的 63 株细菌。使用基质辅助激光解吸/电离（MALDI）。根据制造商关于使用 MALDI-飞行时间（ToF）质谱法的建议，该工作使用了三种主要的微生物样品制备方法：直接涂层法、扩展直接涂层法和甲酸提取法。
当评估培养介质对 MALDI-ToF 质谱法鉴定 NTM 的结果的影响时，对于所有比较参数，都揭示了介质对 NTM 鉴定结果的影响具有统计学意义。
优化样品制备方案并评估新培养方法对鉴定的影响，可以显著提高对临床相关 AFB 组微生物和目前尚未证明具有临床意义的腐生微生物的鉴定质量。
