Pathogenicity characteristics of Enterococcus faecium from diseased black bears

Abstract

The death of several black bears at the black bear breeding base in Yunnan Pingbian Daweishan is a matter of concern. Multiple black bears exhibited decreased appetite or unusual waste, and some were soporific or suffered from vomiting and anhelation. In order to ascertain the cause of death, 16S rDNA gene sequencing and phylogenetic analysis was performed on bacteria isolated from tissue samples obtained from dead bears. The biochemical characteristics of the isolated bacteria were subsequently analyzed using different biochemical test systems. The bacteria can decompose glucose, but it cannot produce gas. The fermentation study of sucrose, lactose, trehalose, glycerol and mannitol yielded positive results; while it was unable to decompose urea or ODC (ornithine decarboxylase). Basic Local Alignment Search Tool (BLAST) analysis of a ~1500-bp DNA product amplified from the 16S rDNA of the bacterial isolate revealed that Enterococcus faecium from black bears is highly similar to other E. faecium isolates in the National Center for Biotechnology Information (NCBI) database, and the highest sequence similarity (99%) was with the reference strain. In addition, mice infected with the E. faecium isolate succumbed to severe damage to the lungs, liver, spleen, myocardium, and kidney tissues. In summary, the isolated E. faecium from dead black bears induced pathological changes in mice.