Abstract: 【Objective】 The aim of this study was to isolate and identify a strain of Klebsiella oxytoca from goat and investigate the pathogenic mechanism of Klebsiella oxytoca in animals.【Method】 The lung tissue samples were collected from Hainan Black goats for bacterial isolation and culture,and the isolates were identified by biochemical test and 16S rRNA gene detection methods,and drug sensitivity test,mouse pathogenicity test, RNA-Seq analysis,and differentially expressed genes (DEGs) analysis on the isolated bacteria were performed.【Result】 One Gram-negative short rod-shaped bacterium was isolated with a smooth round milky colony on tryptic soybean agar medium.The isolated bacteria could decompose glucose,lactose,sucrose and other carbohydrates,and the indole test was positive.16S rRNA genetic testing results showed that the similarity between the isolate and the published sequence was ＞99%, and the isolated strain was identified as Klebsiella oxytoca,which was named KOHN1.The drug susceptibility test results showed that KOHN1 strain was resistant to penicillin,oxacillin,ampicillin,carbenicillin,cephalexin,midecamycin,vancomycin and clindamycin,while it was susceptible to the other 21 antimicrobial agents tested.Acute inflammation such as pulmonary congestion,edema and exudation were observed in histopathological sections of the lungs of mice infected with the isolated strain KOHN1.DEGs enrichment analysis showed that DEGs of inflammatory cytokines and chemokines were highly expressed in lung of mice.【Conclusion】 In this experiment,a strain of Klebsiella oxytoca was successfully isolated,the isolate was highly pathogenic to mice,and the immune response pathway played an important role in the process of bacterial infection,which provided a reference for the subsequent clinical prevention,diagnosis and treatment and drug development of Klebsiella oxytoca.

Key words: Hainan Black goats; Klebsiella oxytoca; isolation and identification; RNA-Seq; immune mechanism