Subspecies Identification and Characterization of Drug Resistance and Virulence Factors in Clinical Strains of <i>Mycobacterium abscessus</i> Complex Isolated from South India.
MABC was identified in 2.25% of clinical samples, with significant resistance mutations found, highlighting the need for improved diagnostic strategies.
Where it sits
this study against the rest of the kpv corpusSummary and findings
This study measured the prevalence and subspecies distribution of Mycobacterium abscessus complex (MABC) in clinical samples from South India, identifying 2.25% of cases (n=25). It characterized resistance-associated mutations and virulence factors, including biofilm formation, in these strains. The study involved 1110 NTM-suspected clinical samples screened over a period from January 2024 to October 2025.
Abstract
<h4>Background</h4><i>Mycobacterium abscessus</i> complex (MABC), comprising <i>Mycobacterium abscessus</i> subsp. <i>abscessus</i> (MABa), <i>Mycobacterium abscessus</i> subsp. <i>bolletii</i> (MABb), and <i>Mycobacterium abscessus</i> subsp. <i>massiliense</i> (MABm), is an emerging group of non-tuberculous mycobacteria with clinically significant infections and challenging treatment outcomes due to extensive antimicrobial resistance. Accurate subspecies identification and characterization of resistance- and virulence-associated determinants are essential for effective disease management. This study aimed to determine the prevalence and subspecies distribution of MABC and to characterize resistance-associated mutations and virulence factors, including biofilm formation.<h4>Methods</h4>A total of 1110 NTM-suspected clinical samples were screened during the study period, between January 2024 and October 2025. Samples negative by GeneXpert MTB/RIF were subjected to Mycobacteria Growth Indicator Tube (MGIT) culture, followed by Ziehl-Neelsen staining and MPT64 antigen testing. Acid-fast bacilli-positive, MPT64-negative isolates were identified as NTM and analyzed using GenoType CM and NTM-DR line probe assays (LPA) for species identification and detection of resistance-associated mutations. A polymerase chain reaction (PCR) assay was optimized to differentiate MABa and MABm. All MABC clinical strains were further characterized for colony morphology (smooth and rough) and biofilm formation. Three biofilm-producing MABa strains (2 rough and 1 smooth) that were detected as macrolide-resistant by NTM-DR were subjected to whole-genome sequencing (WGS).<h4>Results</h4>Among 1110 clinical samples, MABC was identified in 2.25% (<i>n</i> = 25) of cases, while other NTM species accounted for 4.41% (<i>n</i> = 49). Among 25 MABC clinical strains, 14 (56%) were MABm, and 11 (44%) were MABa, as confirmed by both LPA and PCR. LPA-NTM DR detected <i>erm(41)</i> T28 sequevar (<i>n</i> = 9) and C28 mutation (<i>n</i> = 2) among MABa strains, with one strain exhibiting aminoglycoside resistance-associated <i>rrs</i> mutation. Nineteen isolates displayed a smooth morphotype (MABa = 8 and MABm = 11), and six were rough (MABa = 3 and MABm = 3). Biofilm formation was observed in both smooth (<i>n</i> = 5) and rough (<i>n</i> = 4) morphotypes. WGS analysis confirmed <i>erm(41)</i> T28 sequevar, identified a missense mutation (A238G), and revealed genes associated with glycopeptidolipid biosynthesis.<h4>Conclusions</h4>Our findings provide important insights into subspecies identification and genetic determinants associated with drug resistance and virulence in MABC. The biofilm-forming ability observed in both smooth and rough morphotypes emphasizes its potential role in persistence and treatment challenges, emphasizing the need for comprehensive diagnostic strategies.
Background
The paper addresses the increasing concern regarding Mycobacterium abscessus complex, which is known for its resistance to multiple drugs and its virulence factors. Prior studies have indicated that this complex poses significant treatment challenges, particularly in clinical settings. This study is important as it aims to provide insights into the subspecies and their associated drug resistance, which could inform future treatment strategies.
Methods
Not reported in abstract.
Results
Not reported in abstract.
Interpretation
Not reported in abstract.
Key findings
- Not reported in abstract.
Limitations
- Not reported in abstract.