新生麋鹿出血性肺炎病原菌的分离鉴定及生物学特性分析

To clarify the causes of abnormal mortality of newborn Chinese milu （Elaphurus davidianus） at an institution in Beijing， the pathogenic analysis was conducted on pathological tissues from deceased individuals. Based on clinical symptoms， pathological autopsy， bacterial isolation and culture， 16S rRNA gene sequencing and biochemical identification， the cause of death was determined to be hemorrhagic pneumonia induced by mixed infection of Escherichia coli and Streptococcus sp. Antimicrobial susceptibility testing showed that the Streptococcus isolate was sensitive to penicillin， erythromycin， ceftriaxone and meropenem； the Escherichia coli isolate was not fully sensitive to all tested drugs but exhibited intermediate sensitivity to ceftriaxone，meropenem and other drugs. Both isolates were resistant to amphotericin B. Virulence genes detection revealed that E. coli carried seven virulence genes， including AatA， FimC and Mat， while no target virulence genes were detected in Streptococcus. The results of mice pathogenicity tests demonstrated that the mortality rate of Escherichia coli infection alone was 20%， Streptococcus infection alone induced only depressive symptoms， whereas the mortality rate increased to 60% after mixed infection of Escherichia coli and Streptococcus. The findings elucidate the biological and pathogenic characteristics of the mixed infection pathogens responsible for hemorrhagic pneumonia in newborn Chinese Milu， and provide a scientific basis for the clinical diagnosis， treatment and prevention of this disease.