Mycobacterium abscessus (M. abscessus) and Mycobacterium massiliense (M. massiliense) are major pathogens that cause post-surgical wound infection and chronic pulmonary disease. Although they are closely related subspecies of M. abscessus complex, their infections are associated with different drug-resistance and cure rate. In the present study, a loop-mediated isothermal amplification (LAMP) coupled with lateral flow dipstick (LFD) method was developed to simultaneous detect M. abscessus and M. massiliense, via specific erm(41) gene. The amplification was carried out at 65 °C for only 60 min, and the results could be visualized on a lateral flow strip. Positive results only occurred in M. abscessus and M. massiliense, no cross-reaction with other mycobacterial species was observed. Therefore, the cost-effective MABC (M. abscessus complex)–LAMP–LFD method developed here was able to correct the diagnose of M. abscessus and M. massiliense infection in a short time. Thus, this method could be used to guide clinicians in treatment of M. abscessus group infections.

Patients with tuberculosis resistant to isoniazid but susceptible to rifampicin (H^r-R^s TB) remain a neglected demographic, despite a high disease burden and poor outcomes of these patients. The aim of this study was to investigate the characteristics of isoniazid-resistance-related mutations in Mycobacterium tuberculosis and resistance rates to drugs included in WHO-recommended regimens for H^r-R^s patients. Mycobacterium tuberculosis isolates (n = 4922) obtained from national tuberculosis drug-resistance surveillance were subjected to whole-genome sequencing to identify H^r-R^s strains. The minimal inhibitory concentrations (MICs) were established for the H^r-R^s strains to determine the isoniazid resistance levels. We also identified drug-resistance-associated mutations for five drugs (fluoroquinolones, ethambutol, pyrazinamide, streptomycin, and amikacin) in the H^r-R^s strains. Of the 4922 strains, 384 (7.8 %) were H^r-R^s. The subculture of seven strains failed, so 377 (98.2 %) strains underwent phenotypic MIC testing. Among the 384 genotypic H^r-R^s strains, 242 (63.0 %) contained the katG Ser315Thr substitution; 115 (29.9 %) contained the -15C>T in the promoter region of the fabG1 gene; and 16 (4.2 %) contained Ser315Asn in the katG gene. Of the 239 strains with the Ser315Thr substitution, 229 (95.8 %) had MIC ≥ 2 µg/mL, and of the 114 strains with the -15C>T mutation, 103 (90.4 %) had 0.25 µg/mL ≤ MIC ≤ 1 µg/mL. The genotypic resistance rates were 0.8 % (3/384) for pyrazinamide, 2.3 % (9/384) for ethambutol and fluoroquinolones; 39.6 % (152/384) of the strains were resistant to streptomycin, but only 0.5 % (2/384) of the strains were resistant to amikacin. Ser315Thr in katG was the predominant mutation conferring the H^r-R^s phenotype, followed by the fabG1 -15C>T mutation. The combination of rifampicin, pyrazinamide, ethambutol, and levofloxacin should be effective in the treatment of patients with H^r-R^s tuberculosis because the resistance rates for these drugs in China are low.

Objectives: To investigate epidemiological/drug-resistance characteristics and identify potential factors related to drug-resistant and clustered tuberculosis in Sichuan. Methods: A total of 295 Mycobacterium tuberculosis (MTB) isolates were collected from surveillance sites in Sichuan from 2019 to 2021. The minimum inhibitory concentrations (MICs) of 12 anti-TB drugs were acquired using the broth microdilution method, followed by whole-genome sequencing (WGS) analysis. Results: Of 268 MTB isolates with both WGS and drug-susceptibility testing (DST) results, 159 (59.3%, 159/268) strains belonged to the Beijing lineage (L2). Isoniazid had the highest resistance rate (15.3%, 41/268), followed by rifampicin (9.3%, 25/268). The sensitivity of WGS to predict drug resistance varied from 75% to 97.6%, and the specificity was above 96.0% for all. rpoB Ser450Leu (41.7%, 10/24) and katG Ser315Thr (70%, 28/40) were the most frequent mutations in rifampicin and isoniazid resistance isolates, respectively. The clustering rate in Sichuan was 9.3% (25/268), and patients ≤ 24 years old (aOR = 11.697; 95% CI: 0.817–167.463) had a greater risk of clustering. Conclusions: Our findings prove that WGS is a promising tool for predicting drug resistance to isoniazid, rifampicin, ethambutol, moxifloxacin and levofloxacin in Sichuan. The higher resistance rate to isoniazid emphasizes the urgent need for susceptibility testing surveillance and application management. Improving the diagnosis, treatment and management of patients ≤ 24 years old may reduce the transmission of MTB in Sichuan.

Early diagnosis of drug susceptibility for tuberculosis (TB) patients could guide the timely initiation of effective treatment. We evaluated a novel multiplex xMAP TIER (Tuberculosis-Isoniazid-Ethambutol-Rifampicin) assay based on the Luminex xMAP system to detect first-line anti-tuberculous drug resistance. Deoxyribonucleic acid samples from 353 Mycobacterium tuberculosis clinical isolates were amplified by multiplex polymerase chain reaction, followed by hybridization and analysis through the xMAP system. Compared with the broth microdilution method, the sensitivity and specificity of the xMAP TIER assay for detecting resistance was 94.9% (95%CI, 90.0–99.8%) and 98.9% (95%CI, 97.7–100.0%) for rifampicin; 89.1% (95%CI, 83.9–94.3%) and 100.0% (95%CI, 100.0–100.0%) for isoniazid; 82.1% (95% CI, 68.0–96.3%) and 99.7% (95% CI, 99.0–100.0%) for ethambutol. With DNA sequencing as the reference standard, the sensitivity and specificity of xMAP TIER for detecting resistance were 95.0% (95% CI, 90.2–99.8%) and 99.6% (95% CI, 98.9–100.0%) for rifampicin; 96.9% (95% CI, 93.8–99.9%) and 100.0% (95% CI, 100.0–100.0%) for isoniazid; 86.1% (95% CI, 74.8–97.4%) and 100.0% (95% CI, 100.0–100.0%) for ethambutol. The results achieved showed that the xMAP TIER assay had good performance for detecting first-line anti-tuberculosis drug resistance, and it has the potential to diagnose drug-resistant tuberculosis more accurately due to the addition of more optimal design primers and probes on open architecture xMAP system.

Mycobacterial membrane proteins play a pivotal role in the bacterial invasion of host cells; however, the precise mechanisms underlying certain membrane proteins remain elusive. Mycolicibacterium smegmatis (Ms) msmeg5257 is a hemolysin III family protein that is homologous to Mycobacterium tuberculosis (Mtb) Rv1085c, but it has an unclear function in growth. To address this issue, we utilized the CRISPR/Cas9 gene editor to construct Δmsmeg5257 strains and combined RNA transcription and LC-MS/MS protein profiling to determine the functional role of msmeg5257 in Ms growth. The correlative analysis showed that the deletion of msmeg5257 inhibits ABC transporters in the cytomembrane and inhibits the biosynthesis of amino acids in the cell wall. Corresponding to these results, we confirmed that MSMEG5257 localizes in the cytomembrane via subcellular fractionation and also plays a role in facilitating the transport of iron ions in environments with low iron levels. Our data provide insights that msmeg5257 plays a role in maintaining Ms metabolic homeostasis, and the deletion of msmeg5257 significantly impacts the growth rate of Ms. Furthermore, msmeg5257, a promising drug target, offers a direction for the development of novel therapeutic strategies against mycobacterial diseases.

Objective: Given the increase of treatment failure, relapse and acquired resistance observed in isoniazid (INH) resistance, there is an urgent to improve rifampin (RIF) -priority based diagnostic strategies. Therefore, we evaluated the performance of Innovo GenMax MTB-RIF/INH (GenMax), a moderate- complexity automated nucleic acid amplification test (NAAT), for detecting Mycobacterium tuberculosis complex (MTBC) and resistance to RIF and INH.Methods: Analytical sensitivity (limit of detection, LOD) was determined using serial dilutions of Mycobacterium tuberculosis H37Rv (ATCC 27249) strains. Diagnostic accuracy was assessed in clinical sputum specimens against microbiological reference standards (MRS: positive by smear microscopy, culture or Xpert MTB/RIF for diagnosis of TB) and phenotypic drug susceptibility testing (DST). Discordant results were resolved by sequencing resistance genes (IS6110, rpoB, katG, inhA, ahpC) and follow-up diagnosis results.Results: GenMax demonstrated a calculated LOD of 8.8 CFU/mL (95% CI: 7.4-11.4) for MTBC, 674.1 CFU/mL (95% CI: 578.8-923.5) for RIF resistance, and 747.3 CFU/mL (95% CI: 613.7-1081.3) for INH resistance. In clinical evaluation, the sensitivity and specificity for MTBC detection were 97.52% (95% CI: 92.38–99.36) and 93.65% (95% CI: 88.91–96.53), respectively. For RIF and INH resistance, sensitivities were 88.46% (95% CI: 68.72–96.97) and 85.19% (95% CI: 65.39–95.14), with specificity of 92.42% (95% CI: 82.50-97.18) and 94.12% (95% CI: 84.86-98.10).Conclusion: Innovo GenMax MTB-RIF/INH is a rapid and automated assay with high sensitivity for MTBC detection, suitable for decentralized settings. While its performance for RIF/INH resistance detection is competitive with existing assays, its sensitivity remains gaps relative to WHO targets. Further optimization, particularly through expanded probe coverage, is needed to bridge this gap and ensure reliable detection in clinical settings.