Apparent nosocomial adaptation of Enterococcus faecalis predates the modern hospital era
Anna K. Pöntinen, Janetta Top, Sergio Arredondo-Alonso, Gerry Tonkin‐Hill, Ana R. Freitas, Carla Novais, Rebecca A. Gladstone, Maiju Pesonen, Rodrigo Meneses, Henri Pesonen, John A. Lees, Dorota Jamrozy, Stephen D. Bentley, Val F. Lanza, Cármen Torres, Luísa Maria Sobreira Vieira Peixe, Teresa M. Coque, Julian Parkhill, Anita C. Schürch, Rob J. L. Willems, Jukka Corander
Abstract
Enterococcus faecalis is a commensal and nosocomial pathogen, which is also ubiquitous in animals and insects, representing a classical generalist microorganism. Here, we study E. faecalis isolates ranging from the pre-antibiotic era in 1936 up to 2018, covering a large set of host species including wild birds, mammals, healthy humans, and hospitalised patients. We sequence the bacterial genomes using short- and long-read techniques, and identify multiple extant hospital-associated lineages, with last common ancestors dating back as far as the 19th century. We find a population cohesively connected through homologous recombination, a metabolic flexibility despite a small genome size, and a stable large core genome. Our findings indicate that the apparent hospital adaptations found in hospital-associated E. faecalis lineages likely predate the "modern hospital" era, suggesting selection in another niche, and underlining the generalist nature of this nosocomial pathogen.