# Resistance phenotypes and genomic features of Mycobacterium seoulense isolates

## TL;DR

This study examines the antibiotic resistance and genetic diversity of Mycobacterium seoulense, an emerging pathogen, to better understand its clinical implications.

## Contribution

The study provides the first detailed analysis of drug resistance and genomic features of clinical M. seoulense isolates.

## Key findings

- All isolates showed high resistance to minocycline, doxycycline, and amikacin.
- Genomic diversity was observed, with 315 unique genes and two potential virulence genes identified.
- M. seoulense isolates demonstrated the ability to survive within macrophages.

## Abstract

Mycobacterium seoulense (M. seoulense) is an emerging pathogen increasingly associated with infections; however, its resistance phenotypes and genomic characteristics remain largely unknown.

Seven M. seoulense isolates were collected from clinical samples. Drug susceptibility testing was conducted using Sensititre™ SLOMYCO2 susceptibility plates. Whole genome sequencing and supporting bioinformatics analyses were performed to analyze the genomic features.

All M. seoulense isolates (n=7) exhibited growth on 7H10 agar medium containing thiophenecarboxylic acid hydrazide or p-Nitrobenzoic acid, with marked diversity in growth rates in liquid culture. All strains exhibited high minimum inhibitor concentrations (MICs) for minocycline (>8 μg/mL), doxycycline (>8 μg/mL), and amikacin (16-32 μg/mL). The MICs for linezolid, rifabutin, moxifloxacin, ciprofloxacin, streptomycin, clarithromycin, and rifampicin varied among the isolates. High levels of genomic diversity were noted among these strains concerning genome-called single nucleotide polymorphisms and average nucleotide identity. In total, 4,282 genes were shared across all genomes, while 315 unique genes were restricted to one strain. Comparative genomic analysis identified two unique virulence genes encoding a catalase enzyme and a protein involved in capsule biosynthesis and transport. Additionally, all M. seoulense strains demonstrated the ability to survive within macrophages.

The clinical M. seoulense isolates analyzed in this study exhibited varying levels of antibiotic susceptibility, suggesting the potential need for susceptibility testing to guide clinical treatment. Genomic features of these isolates indicated that they are likely pathogenic non-tuberculous mycobacterium, highlighting a need for closer epidemiological monitoring.