Hidden Staphylococcus aureus Carriage: Overrated or Underappreciated?

Area of Science:

• Microbiology
• Infectious Diseases
• Genomics

Background:

• Staphylococcus aureus is a common human commensal bacterium, colonizing approximately one-third of the population.
• Reservoirs for S. aureus include the nasal cavity, skin, and gastrointestinal tract.
• Previous understanding suggested clonal colonization, but next-generation sequencing (NGS) indicates significant resident strain heterogeneity.

Purpose of the Study:

• To investigate the role of low-level gastrointestinal (GI) S. aureus colonization in long-term nosocomial outbreaks.
• To elucidate the epidemiological source of institutional endemicity with methicillin-resistant S. aureus (MRSA) ST228.
• To highlight the utility of NGS in understanding bacterial epidemiology and persistence.

Main Methods:

• Utilized staphylococcal genome sequencing (SGS), a form of next-generation sequencing (NGS).
• Analyzed epidemiological data to trace the origin of MRSA ST228 outbreaks in an institutional setting.
• Correlated low-grade asymptomatic GI colonization with infection control failures.

Main Results:

• Low-level asymptomatic GI persistence of S. aureus was identified as a source of long-term nosocomial outbreaks.
• Institutional MRSA ST228 endemicity was linked to asymptomatic GI colonization, not solely nasal carriage or poor infection control.
• NGS proved powerful in revealing S. aureus epidemiology and identifying stealthy persistence mechanisms.

Conclusions:

• Asymptomatic gastrointestinal S. aureus colonization represents a significant, often overlooked, reservoir for persistent infections and outbreaks.
• Understanding these hidden reservoirs and persistence mechanisms is crucial for effective infection control strategies, particularly for drug-resistant strains like MRSA.
• NGS is an invaluable tool for dissecting bacterial epidemiology and identifying novel pathways of microbial persistence.