Enterococci from Wild Magellanic Penguins (Spheniscus magellanicus) as an Indicator of Marine Ecosystem Health and Human Impact

ABSTRACT

Enterococci are commensals that proliferated as animals crawled ashore hundreds of millions of years ago. They are also leading causes of multidrug-resistant hospital-acquired infections. While most studies are driven by clinical interest, comparatively little is known about enterococci in the wild or the effect of human activity on them. Pharmaceutical pollution and runoff from other human activities are encroaching widely into natural habitats. To assess their reach into remote habitats, we investigated the identity, genetic relatedness, and presence of specific traits among 172 enterococcal isolates from wild Magellanic penguins. Four enterococcal species, 18 lineage groups, and different colonization patterns were identified. One Enterococcus faecalis lineage, sequence type 475 (ST475), was isolated from three different penguins, making it of special interest. Its genome was compared to those of other E. faecalis sequence types (ST116 and ST242) recovered from Magellanic penguins, as well as to an existing phylogeny of E. faecalis isolated from diverse origins over the past 100 years. No penguin-derived E. faecalis strains were closely related to dominant clinical lineages. Most possessed intact CRISPR defenses, few mobile elements, and antibiotic resistances limited to those intrinsic to the species and lacked pathogenic features conveyed by mobile elements. Interestingly, plasmids were identified in penguin isolates that also had been reported for other marine mammals. Enterococci isolated from penguins showed limited anthropogenic impact, indicating that they are likely representative of those naturally circulating in the ecosystem inhabited by the penguins. These findings establish an important baseline for detecting the encroachment of human activity into remote planetary environments.

IMPORTANCE Enterococci are host-associated microbes that have an unusually broad range, from the built hospital environment to the guts of insects and other animals in remote locations. Despite their occurrence in the guts of animals for hundreds of millions of years, we know little about the properties that confer this range or how anthropogenic activities may be introducing new selective forces. Magellanic penguins live at the periphery of human habitation. It was of interest to examine enterococci from these animals for the presence of antibiotic resistance and other markers reflective of anthropogenic selection. Diverse enterococcal lineages found discount the existence of a single well-adapted intrinsic penguin-specific species. Instead, they appear to be influenced by a carnivorous lifestyle and enterococci present in the coastal sea life consumed. These results indicate that currently, the penguin habitat remains relatively free of pollutants that select for adaptation to human-derived stressors.