Ann Clin Microbiol 2025;28(4):21. Impact of nontuberculous mycobacteria on the performance of Xpert MTB/RIF and Xpert MTB/RIF Ultra for the detection of tuberculosis and rifampin resistance: a diagnostic accuracy study
| Concentration (CFU/mL equivalent) | Xpert MTB/RIF | Xpert MTB/RIF Ultra | |||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Ct value (1st/2nd) | Ct value (1st/2nd) | Tm (1st/2nd) | |||||||||||||||||
| NTM strain (1.0 × 106) | MTB (5.0×103) | SPC | Probe A | Probe B | Probe C | Probe D | Probe E | SPC | IS1081/6110 | rpoB1 | rpoB2 | rpoB3 | rpoB4 | rpoB1 | rpoB2 | rpoB3 | rpoB4 | ||
| – | RS | 22.8 | 24.2 | 24.9 | 24.5 | 24.8 | 25.7 | 25.6 | 18.0 | 25.5 | 24.7 | 26.8 | 28.9 | 69.4 | 73.1 | 75.9 | 67.3 | ||
| RR | 22.7 | 22.1 | 23.5 | 22.9 | 23.1 | 0.0 | 27.0 | 19.0 | 23.8 | 24.2 | 27.1 | 23.1 | 69.4 | 74.3 | 73.4 | 73.8 | |||
| M. avium (KMRC 0136-41011) | RS | 21.6/25.3 | 24.7/26.9 | 25.0/27.9 | 24.6/27.2 | 25.0/27.6 | 26.4/28.3 | 26.0/26.0 | 18.2/18.3 | 25.2/25.6 | 24.6/24.9 | 26.5/27.0 | 28.3/28.7 | 69.5/69.5 | 73.3/73.4 | 76.0/76.1 | 67.5/67.5 | ||
| RR | 22.2/24.7 | 24.1/25.3 | 24.7/26.6 | 24.3/25.8 | 24.4/26.1 | 0.0/0.0 | 25.0/0 | 20.6/23.5 | 25.4/0.0 | 24.9/0.0 | 28.1/0.0 | 24.7/0.0 | 69.3/- | 74.4/- | 73.7/- | 73.8/- | |||
| M. intracellulare (ATCC 13950) | RS | 23.8/22.2 | 25.7/23.6 | 26.5/24.3 | 25.7/24.1 | 26.4/24.6 | 27.3/25.7 | 26.0/25.2 | 22.3/19.5 | 29.4/26.7 | 29.0/26.0 | 30.5/28.0 | 31.6/30.0 | 69.4/69.4 | 73.2/73.2 | 75.9/75.9 | 67.2/67.4 | ||
| RR | 23.2/23.8 | 24.7/25.4 | 25.7/26.3 | 25.1/26.1 | 25.4/26.3 | 0.0/0.0 | 25.7/25.5 | 20.8/19.4 | 25.7/23.4 | 25.4/23.6 | 28.7/26.6 | 24.9/22.4 | 69.4/69.5 | 74.3/74.4 | 73.7/73.7 | 73.8/73.8 | |||
| M. kansasii (ATCC 12478) | RS | 23.5/23.4 | 25.0/24.5 | 26.0/25.4 | 25.2/24.6 | 25.6/25.2 | 26.8/26.4 | 25.1/25.8 | 17.5/18.5 | 24.7/26.0 | 23.5/25.0 | 26.0/27.5 | 27.8/29.3 | 69.3/69.3 | 73.2/73.1 | 75.9/75.8 | 67.4/67.3 | ||
| RR | 23.5/24.0 | 26.4/23.4 | 27.0/24.5 | 26.5/23.7 | 26.7/24.2 | 0.0/0.0 | 25.6/26.0 | 21.2/20.3 | 26.3/25.7 | 25.7/25.0 | 29.2/28.1 | 25.4/24.1 | 69.2/69.4 | 74.2/74.2 | 73.7/73.4 | 73.7/73.8 | |||
| M. abscessus subsp. abscessus (ATCC 19977) | RS | 22.0/23.7 | 24.0/24.9 | 24.8/25.8 | 24.2/25.3 | 24.5/25.6 | 25.8/26.6 | 24.8/25.2 | 18.3/18.1 | 23.8/25.7 | 23.6/25.3 | 26.0/27.4 | 30.5/31.1 | 69.6/69.4 | 73.4/73.2 | 76.1/75.9 | 67.6/67.4 | ||
| RR | 23.2/22.7 | 23.9/24.4 | 25.0/25.3 | 24.3/24.8 | 24.5/25.2 | 0.0/0.0 | 25.4/25.3 | 21.1/20.0 | 26.1/25.3 | 25.7/25.0 | 29.1/27.6 | 25.0/27.3 | 69.3/69.2 | 74.2/74.1 | 73.4/73.2 | 73.7/73.6 | |||
| M. abscessus subsp. massiliense (CCUG 48898) | RS | 22.2/23.5 | 26.4/25.5 | 25.1/26.2 | 24.6/26.0 | 25.0/26.0 | 26.3/27.3 | 26.3/25.9 | 17.8/19.4 | 24.0/28.5 | 24.2/27.7 | 25.6/30.0 | 27.7/31.6 | 69.3/69.4 | 73.1/73.1 | 75.8/75.9 | 67.4/67.3 | ||
| RR | 23.0/21.7 | 25.8/23.1 | 26.5/24.0 | 26.1/23.5 | 26.3/23.8 | 0.0/0.0 | 25.1/28.8 | 20.0/19.9 | 23.8/28.9 | 24.2/28.2 | 27.3/31.6 | 22.8/26.0 | 69.3/69.1 | 74.2/73.4 | 73.5/72.8 | 73.8/73.3 | |||
| M. gordonae (ATCC 14470) | RS | 21.7/21.7 | 22.5/21.6 | 23.6/22.7 | 22.7/21.8 | 23.3/22.4 | 24.2/23.3 | 26.1/25.0 | 18.4/18.5 | 25.5/24.8 | 24.8/24.3 | 26.9/26.0 | 29.0/28.0 | 69.3/69.3 | 73.1/73.2 | 75.8/75.9 | 67.4/67.4 | ||
| RR | 23.8/24.0 | 24.7/26.4 | 25.7/27.1 | 25.0/26.8 | 25.3/27.0 | 0.0/0.0 | 25.2/27.6 | 22.2/20.3 | 27.2/25.5 | 26.8/25.2 | 30.1/28.8 | 26.1/25.5 | 69.3/69.4 | 74.4/74.3 | 73.6/73.5 | 73.7/73.8 | |||
| M. chelonae (ATCC 35752) | RS | 22.6/22.7 | 24.4/23.5 | 24.9/24.5 | 24.5/23.6 | 25.1/24.2 | 26.1/25.2 | 24.7/25.4 | 17.7/19.0 | 25.0/25.9 | 24.1/25.0 | 26.1/27.0 | 28.5/28.7 | 69.4/69.2 | 73.2/73.0 | 75.9/75.7 | 67.4/67.3 | ||
| RR | 23.3/23.8 | 24.3/25.8 | 25.1/26.5 | 24.6/26.3 | 24.9/26.4 | 0.0/0.0 | 24.4/25.4 | 21.5/19.9 | 25.6/24.8 | 25.2/24.1 | 28.3/28.0 | 24.5/23.6 | 69.4/69.4 | 74.5/74.3 | 73.8/73.5 | 73.8/73.9 | |||
| M. fortuitum (KMRC 0136-60004) | RS | 23.2/24.8 | 25.4/25.7 | 26.1/26.7 | 25.4/26.1 | 26.0/26.4 | 27.2/27.5 | 25.7/27.1 | 17.7/21.0 | 24.2/29.3 | 23.8/28.5 | 26.0/30.6 | 28.6/31.0 | 69.2/69.3 | 73.0/73.1 | 75.7/75.8 | 67.3/67.2 | ||
| RR | 21.7/22.5 | 23.6/23.7 | 24.4/24.6 | 23.7/24.4 | 24.3/24.5 | 0.0/0.0 | 28.3/26.2 | 19.5/20.6 | 27.0/26.2 | 26.9/25.8 | 31.1/29.3 | 24.9/25.3 | 69.0/69.3 | 73.3/74.2 | 72.7/73.4 | 73.7/73.7 | |||
Values in bold denote mutant Tm.
Abbreviations: MTB, Mycobacterium tuberculosis; RIF, rifampin; CFU, colony-forming unit; Ct, cycle threshold; Tm, melting peak temperature; NTM, nontuberculous mycobacteria; SPC, specimen processing control; KMRC, Korea Mycobacterium Resource Center; ATCC, American Type Culture Collection; CCUG, Culture Collection University of Göteborg; RS, rifampin-susceptible reference strain (H37Rv, ATCC 27294); RR, rifampin-resistant clinical isolate with S450L mutation.