Pathogenicity of Enterococci

Abstract

Enterococci are unusually well adapted for survival and persistence in a variety of adverse environments, including on inanimate surfaces in the hospital environment and at sites of infection. This intrinsic ruggedness undoubtedly played a role in providing opportunities for enterococci to interact with other overtly drug-resistant microbes and acquire additional resistances on mobile elements. The rapid rise of antimicrobial resistance among hospital-adapted enterococci has rendered hospital-acquired infections a leading therapeutic challenge. With about a quarter of a genome of additional DNA conveyed by mobile elements, there are undoubtedly many more properties that have been acquired that help enterococci persist and spread in the hospital setting and cause diseases that have yet to be defined. Much remains to be learned about these ancient and rugged microbes, particularly in the area of pathogenic mechanisms involved with human diseases.

FIGURE 1

Animal hosts that have been associated with enterococcal colonization. A simplified tree of life with blue shading indicating animals from which enterococci have been isolated. Corresponding geologic periods are indicated on the left. Reproduced with permission from reference .

FIGURE 2

Routes of dissemination of enterococci from the intestinal reservoir of a hospitalized patient. Bacteria from the intestine can seed infections throughout the body and contaminate surfaces, leading to patient-to-patient spread. Reproduced with permission from reference .

FIGURE 3

Population structure of E. faecium and E. faecalis based on comparisons of whole genomes. (A) RAxML tree of 1,344 single copy core genes found in 73 E. faecium genomes, showing the clade structure of the E. faecium population. Reproduced with permission from reference . (B) Phylogeny of 515 E. faecalis isolates based on 1,293 conserved core genes found in 99% of isolates. The L1, L2, and L3 lineages are highlighted with red, purple, and turquoise lines, respectively. Reproduced with permission from reference .