Probe amplifications in the Xpert MTB/RIF Ultra assay for non-tuberculous mycobacteria identified from diabetes mellitus and chronic kidney disease patients in Ethiopia
Abstract The demand for resources for mycobacterial culture makes diagnosing non-tuberculous mycobacteria (NTM) difficult. This study assessed probe amplifications in the Xpert MTB/RIF Ultra (Xpert Ultra) and Xpert MTB/RIF assays for different NTM species identified from diabetes mellitus (DM) and c...
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| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Nature Portfolio
2025-05-01
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| Series: | Scientific Reports |
| Subjects: | |
| Online Access: | https://doi.org/10.1038/s41598-025-03716-y |
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| Summary: | Abstract The demand for resources for mycobacterial culture makes diagnosing non-tuberculous mycobacteria (NTM) difficult. This study assessed probe amplifications in the Xpert MTB/RIF Ultra (Xpert Ultra) and Xpert MTB/RIF assays for different NTM species identified from diabetes mellitus (DM) and chronic kidney disease (CKD) patients. Since the sources of NTM isolates were DM and CKD patients, the study was limited to those patients. We ran the Xpert Ultra and Xpert MTB/RIF assays on 87 NTM culture isolates identified from DM (41 isolates) and CKD (46 isolates) patients, as well as seven distinct NTM ATCC strains. We also assessed the frequency of NTM species in 97 Xpert Ultra negative clinical specimens, which had probe amplification. Moreover, we assessed the effect of mixed NTM and M. tuberculosis infection and the presence of other bacteria (five gram-positive and five gram-negative) on probe amplification. Data were analyzed using SPSS version 27. Descriptive statistics were used to characterize each study variable. The cycle threshold (CT) values were compared across categories using the Mann-Whitney U and Kruskal-Wallis tests. The GeneXpert assays produced negative results for all 87 NTM isolates. Of them, 88.5% and 78.2% had probe amplification in the Xpert Ultra assay and Xpert MTB/RIF assay, respectively. The most often amplified probe was rpoB2 (77, 88.5%), followed by rpoB4 (10, 11.5%) in the Xpert Ultra, and Probe C (64, 73.6%), followed by Probe A (7, 8.0%) in the Xpert MTB/RIF. The median CT values for rpoB1, rpoB4, and rpoB2 were 30.9, 30.55, and 28.3, respectively. Whereas, for Probe C and Probe A, it was 29.2 and 26.3, respectively. The amplified probes were similar for NTM species. The rpoB2 CT value differed significantly among the NTM species (X2 = 18.857, p = 0.016), with M. simiae having a higher median CT value and M. gordonae, M. asiaticum, and M. scrofulaceum having lower median CT values. Likewise, the CT value for Probe C was different among the NTM species (X2 = 13.199; p = 0.041). Later, NTM was identified in 13.40% (13/97) of specimens with probe amplification in the direct specimen. M. tuberculosis isolates showed a lower CT value for each probe than NTM isolates. The CT value of rpoB2 for samples found to have NTM in the culture was lower than the CT value of samples with a negative culture result (X2 = 2.949, P = 0.015). Mixed NTM and MTB, and the presence of other bacteria, did not have an effect on probe amplifications in the Xpert Ultra assay. The rpoB probe amplifications with weak signals observed in Xpert Ultra assay negative specimens may help to suggest the presence of NTM species, mainly when TB was ruled out. However, it needs further studies with a larger sample size, including larger cohorts of clinical specimens. |
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| ISSN: | 2045-2322 |