Abstract: Enterococcus faecium, as an opportunistic pathogen in the human and animal intestines, could cause endocarditis and sepsis in the host under certain conditions. Recently, multiple studies indicated that Enterococcus faecium, antimicrobial resistance and pathogenicity of Enterococcus faecium in food animal and wild animal are increasing, but there are fewer studies about AMR in the wild animal. In order to explore the cause of the sudden death of a red-bellied squirrel in Beijing Daxing Wildlife Park, gross autopsy, pathological tissue section, pathogenic bacteria isolation, antibiotic susceptibility testing and pathogenicity analysis were performed on the dead red-bellied squirrel. Results showed that blue flora with short chains of circular or oval shape was observed in lung and kidney sections, and bacteria pathogen were isolated from lung, liver, spleen and abdominal effusion. Antibiotic susceptibility tests have shown that the isolated strains are highly resistant to sulfisoxazole and telomectin; The results of whole genome sequencing showed that the isolated strains all belonged to Enterococcus faecium ST-324, and all carried the virulence gene efaAfm and antibiotic resistance genes tetM and msrC; the core genome single nucleotide polymorphisms (SNPs) analysis showed no significant differences. Animal pathogenicity tests suggested that isolated strains have pathogenicity. The results suggested that the cause of death of the squirrel was sepsis caused by Enterococcus faecium infection.

Key words: wild animals, red-bellied squirrel, Enterococcus faecium, whole genome sequencing