Non-pigmented rapidly growing mycobacteria smooth and rough colony phenotypes pathogenicity evaluated using in vitro...

Area of Science:

• Microbiology
• Infectious Diseases
• Bacterial Pathogenesis

Background:

• Non-pigmented rapidly growing mycobacteria (NPRGM) are increasingly significant in infections due to antimicrobial resistance.
• NPRGM exhibit rough and smooth colony phenotypes, with conflicting reports on the virulence of rough variants.

Purpose of the Study:

• To evaluate the differential pathogenicity of rough and smooth colony variants of NPRGM.
• To compare in vitro and in vivo virulence of these phenotypes using clinical and collection strains.

Main Methods:

• Utilized in vitro macrophage models to assess phagocytosis rates.
• Employed the Galleria mellonella larvae model for in vivo pathogenicity assessment.
• Tested strains of Mycobacterium abscessus, Mycobacterium fortuitum, and Mycobacterium chelonae.

Main Results:

• Rough variants of M. abscessus and M. fortuitum showed higher phagocytosis in macrophages and reduced larval survival compared to smooth variants.
• No significant differences in phagocytosis or larval survival were observed between colonial variants of M. chelonae.
• In vivo results correlated with in vitro findings for M. abscessus and M. fortuitum.

Conclusions:

• Colonial phenotype influences the pathogenicity of certain NPRGM species, specifically M. abscessus and M. fortuitum.
• The clinical significance of NPRGM colonial variants may need re-evaluation based on differential virulence.
• Further research is warranted to understand species-specific variations in NPRGM virulence factors.