Infectious Disease Publications
Long-term colonization dynamics of Enterococcus faecalis in implanted devices in research macaques. Appl Environ Microbiol 2018;Abstract.
Enterococcus faecalis is a common opportunistic pathogen that colonizes cephalic recording chambers (CRCs) of macaques used in cognitive neuroscience research. We previously characterized 15 strains isolated from macaques at our institution in 2011. The goal of this study was to examine how a 2014 protocol change prohibiting antimicrobials within CRCs affected colonizing strains. We collected 20 isolates from 10 macaques between 2013-2017 for comparison to four previously characterized 2011 isolates with respect to sequence type (ST) distribution, antimicrobial resistance, biofilm formation, and changes in genes that might confer a survival advantage. ST4 and ST55 were predominant among 2011 isolates, whereas the less antimicrobial-resistant lineage ST48 emerged to dominance after 2013. Two macaques remained colonized by ST4 and ST55 strains for five and four years, respectively. While the antimicrobial resistance and virulence factors identified in these ST4 and ST55 strains remained relatively stable, we detected an increase in biofilm formation ability over time in both isolates. We also found that ST48 strains were typically robust biofilm formers, which could explain why this ST increased in prevalence. Finally, we identified mutations in the DNA mismatch repair genes and in separate ST55 and ST4 strains, and confirmed that strains bearing these mutations displayed a hypermutator phenotype. The presence of a hypermutator phenotype may complicate future antimicrobial treatment for clinically relevant infections in macaques. is a common cause of healthcare-associated infections in humans, largely due to its ability persist in the hospital environment, colonize patients, acquire antimicrobial resistance, and form biofilms. Understanding how enterococci evolve in healthcare settings provides insight into factors affecting enterococcal survival and persistence. Macaques used in neuroscience research have long-term cranial implants that, despite best practices, often become colonized by This provides a unique opportunity to non-invasively examine the evolution of enterococci on a long-term indwelling device. We collected strains from cephalic implants over a seven-year period and characterized sequence type, antimicrobial resistance, virulence factors, biofilm production and hypermutator phenotypes. Improved antimicrobial stewardship allowed a less-antimicrobial-resistant strain to predominate at the implant interface, potentially improving antimicrobial treatment outcomes if future clinical infections occur. Biofilm formation appears to play an important role in persistence of associated with these implants.