Genotypic and Phenotypic Characterization of Fecal Staphylococcus epidermidis Isolates Suggests Plasticity to Adapt to Different Human Body Sites

Staphylococcus epidermidis is a commensal species that has been increasingly identified as a nosocomial agent. Despite the interest, little is known about the ability of S. epidermidis isolates to adapt to different ecological niches through comparisons at genotype or phenotype levels. One niche where S. epidermidis has been reported is the human gut. Here, we present three S. epidermidis isolated from feces and show that they are not phylogenetically distinct from S. epidermidis isolated from other human body sites. Both gut and skin strains harbored multiple genes associated with biofilm formation and showed similar levels of biofilm formation on abiotic surfaces. High-throughput physiological tests using the BIOLOG technology showed no major metabolic differences between isolates from stool, skin or cheese, while an isolate from bovine mastitis showed more phenotypic variation. Although all strains showed the ability to metabolize glycine-conjugated bile acids, the gut isolates exhibited faster anaerobic growth in the presence of bile salts compared to isolates of skin origin. Interestingly, skin isolates were able to adapt to these conditions within 24-48 h, suggesting that S. epidermidis has the genomic potential to adapt to the different locations of the human body.