1. INTRODUCTION
Antimicrobial resistance (AMR) is one of the major Global Health challenges of the 21st century, and annually kills thousands of people in the world (Cassini et al., 2019; Hernando-Amado, Coque, Baquero, & Martínez, 2019). One Health and Global Health approaches are necessaries to combat the emergence, evolution and spread of AMR (Hernando-Amado et al. , 2019). In this regard, wildlife has been suggested as reservoirs, disseminators or bio-indicators of AMR in the environment (Borges et al., 2017; Dolejska & Literak, 2019;Sacristán et al. , 2020); however, threatened wildlife species are being colonized by antibiotic resistant bacteria, but there are critical data gaps and research needs to understand the role and the real impact of AMR on wildlife (Larsson et al. , 2018; Fuentes-Castillo et al., 2020; Ramey & Ahlstrom, 2020).
The Brazilian merganser (Mergus octosetaceus Vieillot, 1817) is one of the most threatened avian species in the Americas and one of the most threatened waterfowl in the world, classified as Critically Endangered by the International Union for Conservation of Nature (Lamas & Lins, 2009; BirdLife International, 2019). It is estimated that its population does not exceed 250 mature individuals in nature but, thanks to conservation breeding programs, it has been possible to successfully reproduce the species ex-situ (BirdLife International, 2019).
In this study, using microbiological and whole genome sequencing tools, we investigated a fatal sepsis caused by an antibiotic-resistant bacterium in a critically endangered Brazilian merganser. In this regard, the resistome (antibiotics, heavy metals, and disinfectants), virulome, and epidemiological characteristics of the pathogen were analyzed.