Distinct clonal lineages and within-host diversification shape invasive Staphylococcus epidermidis populations

Area of Science:

• Microbiology
• Infectious Diseases
• Genetics

Background:

• Staphylococcus epidermidis is a common skin bacterium and a leading cause of infections linked to medical implants.
• Understanding the factors that enable S. epidermidis to cause infection is crucial for developing effective treatments.

Purpose of the Study:

• To identify specific genetic and phenotypic characteristics of S. epidermidis that contribute to infection establishment.
• To investigate how S. epidermidis adapts to the infection environment within a host.

Main Methods:

• Analysis of S. epidermidis populations from prosthetic joint infections in 23 patients.
• Comparison of invasive and colonizing isolates, including patient-matched nasal and invasive strains.
• Genotypic analysis focusing on the mobilome and specific gene loci, alongside phenotypic assessments.

Main Results:

• Invasive S. epidermidis strains exhibit enhanced biofilm formation, growth in nutrient-poor conditions, and antibiotic resistance.
• Specific genetic elements, including IS256, SCCmec, and novel chromosomally integrated phages, were associated with infection.
• Within-host evolution led to subpopulations with altered genes (e.g., agrC, AckA) and deleted mobile elements.

Conclusions:

• S. epidermidis possesses adaptable genetic and phenotypic traits that facilitate its transition from commensal to pathogen.
• The mobilome plays a significant role in S. epidermidis's adaptation to infection.
• Understanding these adaptive mechanisms is key to combating implant-associated infections.