Mycobacterium mageritense-associated refractory cutaneous infection and lymphadenitis in an immunocompetent adult: insights from genomic sequencing

Nontuberculous mycobacteria are increasingly recognized as causes of chronic and refractory skin and soft tissue infections, even in individuals without immunodeficiency. Among them, Mycobacterium mageritense is a rare, rapidly growing species that can lead to persistent lesions requiring prolonged antimicrobial therapy. Reports of M. mageritense infections involving both the skin and regional lymph nodes are limited, and this case adds new clinical and genomic insights.

A 48-year-old previously healthy man presented with a slowly enlarging cutaneous lesion on his lower leg and ipsilateral inguinal lymphadenitis. Empirical antibacterial therapy with β-lactams and macrolides was ineffective. Wound cultures subsequently grew M. mageritense, confirmed by whole-genome sequencing. Several antimicrobial regimens were attempted, and the final successful therapy consisted of oral levofloxacin and minocycline for 4 months, leading to complete clinical resolution. Genomic analysis identified resistance-related genes, including erm(40), aac(2')-Ib, tet(V), and RbpA, although in vitro minimum inhibitory concentrations showed variable susceptibility. Phylogenetic comparison revealed that the isolate was closely related to previously reported M. mageritense strains from Japan.

This case demonstrates that M. mageritense can cause cutaneous infection with secondary lymphadenitis in an immunocompetent host. Accurate species identification using molecular or genomic methods and selection of appropriate combination antibiotic therapy based on susceptibility testing are crucial for successful management of such infections.