Genetic Diversity, Antimicrobial Resistance, and Pathogenic Potential of Pulmonary Escherichia coli Isolates from Forest Musk Deer with Fatal Hemorrhagic Pneumonia

Forest musk deer (Moschus berezovskii) is an endangered species with high medicinal value.Hemorrhagic pneumonia, characterized by acute onset and high mortality, frequently occurs in captive forest musk deer, seriously restricting captive breeding.However, its etiological agents and pathogenesis remain unclear.In this study, 43 lung tissue samples were collected from forest musk deer that died of hemorrhagic pneumonia between 2023 and 2025.Exploratory metatranscriptomic analysis of 3 selected samples indicated bacterial predominance, with several opportunistic pathogens, including Escherichia coli (E.coli), Pasteurella multocida (P.multocida), and Acinetobacter baumannii (A.baumannii), showing relatively high abundance.Bacterial isolation identified E. coli as the most frequent species (39/89; 43.82%).The isolates exhibited resistance to multiple commonly used antimicrobials; ampicillin (AMP) resistance exceeded 50% in each year.Multilocus sequence typing (MLST) identified 16 assigned sequence types (STs), including ST357, ST224, and ST95, as well as 4 unassigned profiles among the 39 isolates.Representative isolates induced hemorrhagic lung lesions in mice.These findings indicate an association between E. coli and hemorrhagic pneumonia in forest musk deer, providing a basis for disease surveillance and control.