Infection and Drug Resistance (Jun 2022)

Doubled Nontuberculous Mycobacteria Isolation as a Consequence of Changes in the Diagnosis Algorithm

  • Chen S,
  • Wang F,
  • Xue Y,
  • Huo F,
  • Jia J,
  • Dong L,
  • Zhao L,
  • Jiang G,
  • Huang H

Journal volume & issue
Vol. Volume 15
pp. 3347 – 3355

Abstract

Read online

Suting Chen,* Fen Wang,* Yi Xue, Fengmin Huo, Junnan Jia, Lingling Dong, Liping Zhao, Guanglu Jiang, Hairong Huang National Clinical Laboratory on Tuberculosis, Beijing Key Laboratory for Drug-Resistant Tuberculosis Research, Beijing Chest Hospital, Capital Medical University, Beijing Tuberculosis and Thoracic Tumor Institute, Beijing, China*These authors contributed equally to this workCorrespondence: Hairong Huang, Email [email protected]; Guanglu Jiang, [email protected]: Nontuberculous mycobacteria (NTM) and their associated diseases remain neglected. Through minor modifications in our diagnostic algorithm, we observed an unexpected higher number of cultivable NTM isolates. Therefore, a retrospective study was performed thoroughly to investigate the effect of changed laboratory procedures on NTM isolation in a specialized tuberculosis hospital.Methods: NTM isolation rates and composition of NTM species were compared for the two diagnostic algorithms: (1) by using traditional p-nitrobenzoic acid (PNB) selective medium as a preliminary test to identify NTM isolates among the positive cultures (procedure I) and (2) by using the MPT64 antigen detection method to distinguish between Mycobacterium tuberculosis complex (MTBC) isolates and possible NTM isolates after a positive MGIT960 liquid culture (procedure II).Results: The NTM isolation rate in procedure II was significantly higher than the procedure I (18.08% vs 9.71%; P< 0.001). A noticeable increase in the ratio of NTM isolates among the identified mycobacteria was observed over the studied years (ie, from 58.18% in 2019 to 72.93% in 2021), which indicated a more precise prescription of species identification test after prompt information was provided in procedure II. In addition, the consistency of the identified species using multiple specimens from the same patient did not present a significant difference between the procedures.Conclusion: According to our study, NTM infection might be far more underestimated than it is. A diagnostic procedure combining MGIT960 culture and MPT64 antigen detection could timely and easily identify clues of NTM isolates and improve the diagnosis of NTM infections.Keywords: tuberculosis, nontuberculous mycobacteria, p-nitrobenzoic acid, MPT64 antigen, species

Keywords