Staphylococcus aureus small colony variants: a challenge to microbiologists and clinicians

Area of Science:

• Microbiology
• Infectious Diseases
• Bacterial Pathogenesis

Background:

• Staphylococcus aureus can evade antibiotic treatment by forming small colony variants (SCVs).
• SCVs are slow-growing subpopulations with distinct characteristics, often implicated in persistent and recurrent infections.
• Their small size on agar is frequently linked to auxotrophy for hemin or menadione, essential for electron transport.

Purpose of the Study:

• To explore the pathogenic role and survival strategies of Staphylococcus aureus SCVs.
• To investigate the challenges SCVs pose to clinical microbiology diagnostics and treatment.
• To understand the metabolic adaptations of SCVs, such as the arginine deiminase pathway.

Main Methods:

• Analysis of clinical and experimental Staphylococcus aureus small colony variants (SCVs).
• Phenotypic characterization including colony size, pigmentation, and hemolytic activity.
• Transcriptomic studies of site-directed mutants to investigate metabolic pathways.

Main Results:

• SCVs exhibit unique traits, including small colony size, non-pigmentation, and non-hemolysis, complicating identification and susceptibility testing.
• Evidence supports the pathogenic role of SCVs in persistent and recurrent Staphylococcus aureus infections.
• SCVs may utilize the arginine deiminase pathway for ATP production and to neutralize intracellular acidity.

Conclusions:

• Staphylococcus aureus SCVs present significant challenges in clinical settings, requiring tailored diagnostic and therapeutic approaches.
• Antimicrobial agents with intracellular activity are recommended for treating SCV infections due to their intracellular persistence.
• The arginine deiminase pathway is a key metabolic adaptation enabling SCV survival in challenging environments.