# Analysis of nontuberculous mycobacteria laboratory detection data from a designated hospital in Henan Province, China

## TL;DR

This study analyzed NTM detection data from a hospital in Henan, China, finding rising isolation rates and identifying M. intracellulare as the most common species.

## Contribution

The study provides new insights into NTM species distribution and detection trends in central China.

## Key findings

- NTM isolation rates increased from 10.76% to 16.37% between 2020 and 2024.
- M. intracellulare was the most common NTM species identified (79.51%).
- GeneXpert-negative cases with low Ct values often tested positive for MAC.

## Abstract

Nontuberculous mycobacteria (NTM) infections are emerging globally, yet epidemiological data from central China remain limited. This study analyzed mycobacterial culture and identification data from Henan Provincial Chest Hospital (2020–2024) to assess NTM detection patterns and species distribution.

This retrospective laboratory surveillance study analyzed mycobacterial culture and species identification data from Henan Provincial Chest Hospital (January 2020–December 2024). Cultures were performed using the MGIT system with MPB64 antigen detection for MTBC and PNB growth for presumptive NTM identification. Species identification employed DNA microarray targeting the 16–23 S rRNA internal transcribed spacer region. Clinical data (symptoms, radiology, comorbidities), repeated cultures per ATS guidelines, and treatment outcomes were not available. GeneXpert MTB/RIF-negative cases with cycle threshold less than 42 from 2022 to 2024 were analyzed retrospectively.

Among 6,939 culture-positive specimens, 962 (13.86%) were identified as NTM, with annual isolation rates increasing from 10.76% to 16.37%. Of these 962 NTM cases, 532 isolates (55.3%) underwent DNA microarray species identification, revealing M. intracellulare as predominant (79.51%, 423/532), followed by M. abscessus complex (10.53%, 56/532), M. kansasii (4.32%, 23/532), M. avium (3.01%, 16/532), and M. fortuitum (1.69%, 9/532). Among 532 NTM isolates undergoing species identification, males (59.77%) and elderly patients (> 60 years) predominated. In a subgroup of 230 patients with GeneXpert MTB/RIF-negative results but cycle threshold (Ct) values < 42, 101 were identified as NTM-positive. Notably, 94.25% of these cases were attributed to the Mycobacterium avium complex (MAC), with 93 showing low Ct for probe A and 7 for probe C.

NTM isolation rates are rising in Henan Province, with M. intracellulare as the predominant species. GeneXpert-negative cases with low Ct values for probe A may benefit from supplementary acid-fast staining and species identification to enhance early NTM detection, findings represent laboratory detection patterns from single specimens and cannot distinguish colonization from clinically significant disease per ATS/IDSA diagnostic criteria.