Optimized analysis parameters of variant calling for whole genome-based phylogeny of Mycobacteroides abscessus

Mycobacteroides abscessus subspecies: a comparative genomic analysis reveals unique metabolic activities and drug resistance patterns

BACKGROUND

Mycobacteroides abscessus poses a considerable and growing threat to public health due to its resistance against most antibiotics and low cure rate. For a comprehensive understanding of the genomic characteristics and drug resistance mechanisms of M. abscessus, clinical isolates from diverse sources were collected and analyzed.

RESULTS

The clinical M. abscessus complex analyzed herein primarily comprised two subspecies: Mycobacteroides abscessus subsp. abscessus and Mycobacteroides abscessus subsp. massiliense. Furthermore, comparative genomic and single nucleotide polymorphism analyses revealed distinct metabolic activities among subspecies. Subsequent examination of core hub gene mutations confirmed the presence of distinct metabolic and biosynthetic pathways between M. abscessus subspecies, which may have contributed to their differential drug resistance and may aid in providing targeted interventions. Understanding this subtle genomic variation is crucial for improving treatment strategies and patient outcomes. Additional analyses identified potential novel amikacin and moxifloxacin resistance genes, offering a promising avenue for investigating M. abscessus drug resistance.

CONCLUSIONS

Through comparative genomic analysis, we revealed the unique metabolic activities of M. abscessus subsp. abscessus and M. abscessus subsp. massiliense, providing a scientific basis for future diagnostic and personalized management strategies. Identifying possible novel amikacin and moxifloxacin resistance genes within these subspecies offers insights for future drug development efforts and enhances our understanding of the mechanisms underlying M. abscessus drug resistance.

Whole-Genome Sequencing and Drug-Susceptibility Analysis of Serial Mycobacterium abscessus Isolates from Thai Patients

Mycobacterium abscessus is an important pathogen that can cause serious human diseases and is difficult to treat due to antibiotic resistance. In this study, we analyzed, using whole-genome sequence (WGS) data, M. abscessus strains serially isolated from patients at various time intervals. We undertook genetic diversity analysis between subspecies, mutation-rate estimation and identification of drug-resistant mutations with minimum inhibitory concentration (MIC) analysis. Clonal isolates of M. abscessus:—subsp. abscessus (MAB) and subsp. massiliense (MMAS)—causing persistent infection through time, differed by 0−7 and 0−14 SNPs, respectively, despite being isolated 1 to 659 days apart. Two cases caused by MMAS differed by ≥102 SNPs at 350 days apart and were regarded as examples of reinfection. Isolates collected ≤7 days apart exhibited a high mutation rate (133.83 ± 0.00 SNPs/genome (5 Mb)/year for MMAS and 127.75 SNPs/genome (5 Mb)/year for MAB). Mutation rates declined in a time-dependent manner in both subspecies. Based on isolates collected > 180 days apart, MMAS had a significantly higher average mutation rate than MAB (2.89 ± 1.02 versus 0.82 ± 0.83 SNPs/genome (5 Mb)/year, (p = 0.01), respectively). All well-known drug-resistance mutations were found to be strongly associated with high MIC levels for clarithromycin and ciprofloxacin. No known mutations were identified for strains resistant to linezolid and amikacin. MAB strains in the study were susceptible to amikacin, while most MMAS strains were susceptible to clarithromycin, amikacin and linezolid. No hetero-resistance was found in the strains analyzed. Our study reports the genetic diversity and mutation rate of M. abscessus between the two major subspecies and confirms the drug resistance-associated mutations. Information about drug-resistance and associated mutations can be applied in diagnosis and patient management.