Abstract:[Background] Klebsiella pneumoniae, one of the common opportunistic pathogens after Escherichia coli, can lead to hemorrhagic enteritis and systemic sepsis in giant pandas (Ailuropoda melanoleuca). [Objective] To identify the biological characteristics of K.pneumoniae from giant pandas and provide scientific guidance for the prevention and control of the disease. [Methods] The biofilm formation, high viscosity, drug resistance, and 15 common virulence genes of 46 strains of K.pneumoniae from A.melanoleuca were studied via crystal violet staining, string test, K-B disk diffusion method, and PCR, respectively. Further, we selected an isolate (pneumoniae-X-5) that may be pathogenic according to the above biological characteristics to study its pathogenicity in mice. [Results] All the 46 strains of K.pneumoniae could form capsule, among which 12 strains showed the phenotype of high viscosity and 65% (30/46) of the strains could form biofilm. Among the strains, 58% (27/46) were multi-drug resistant and 100% were resistant to ampicillin, oxacillin, penicillin, and vancomycin. Of the virulence genes, ureA had the highest detection rate of 91.30% (42/46). The LD50 of pneumoniae-X-5 in mice was 8.9×104 CFU/mL. The mice challenged with this strain had thickened alveolar septa, inflammatory cell infiltration, hepatocyte degeneration and necrosis, splenic congestion, separation of duodenal mucosal epithelium and lamina propria, and partial cell necrosis in the lamina propria. The spleen contained the highest amount of bacteria in the dead mice, followed by the liver. [Conclusion] This study elucidates the multi-drug resistance, biofilm formation, high viscosity and other pathogenic characteristics of K.pneumoniae from A.melanoleuca, providing a scientific basis for the prevention, control, and clinical treatment of K.pneumoniae disease in A.melanoleuca.
