LAUSR

Simple Summary Klebsiella pneumoniae (K. pneumoniae) can cause a multitude of infectious diseases in humans and animals. In this study, we isolated and identified a strain of K. pneumoniae from Hainan Black goat by using conventional microbiology techniques. Through these and combined with the RNA sequencing (RNA-seq) method, the molecular mechanism of the interaction between K. pneumoniae and animals was able to be better understood. The pathogenic mechanism of K. pneumoniae to animals was explored by establishing the mouse infection model. Our results revealed that K. pneumoniae induced bacteremia and mild pulmonary inflammation in mice by intraperitoneal injection. These results provided a theoretical foundation for subsequent diagnosis and treatment research on the diseases caused by K. pneumoniae. Abstract K. pneumoniae is an opportunistic pathogen that leads to widespread infection in humans and animals, seriously threatening human health and animal husbandry development. In our research, we investigated the biological characteristics of the isolate by using a 16S rRNA gene sequencing, biochemical assay, and drug sensitivity test. Moreover, the pathogenicity study, including the bacteria load determination, the histopathology examination, and the RNA sequencing was carried out to explore whether the isolate could cause lung injury in mice through intraperitoneal injection. The results indicated that the isolate was identified as K. pneumoniae and named as KPHN001. The drug susceptibility test showed that KPHN001 was only sensitive to polymyxin B and furazolidone, and was resistant to other 28 antibiotics. In the bacteria load determination, the highest bacterial load of the organs was found in the spleen, and abundant bacterial colonization was also found in the lung. The histopathology showed the mainly acute inflammations in the lung were due to congestion, edema, and exudation. RNA-seq analysis revealed that the differentially expressed genes (DEGs) of inflammatory cytokines and chemokines were expressed massively in mice. In the present research, the biological characteristics and pathogenesis of clinically isolated K. pneumoniae were systematically studied, revealing the pathogenic mechanism of K. pneumoniae to animals, and providing a theoretical basis for the following prevention, control, and diagnosis research.