Abstract: Klebsiella pneumoniae is a opportunistic pathogen associated with acquired infections and is listed by the World Health Organization （WHO） as a drug-resistant pathogen that urgently needs to develop new antibiotics.Siderophores is an important virulence factor for K.pneumoniae to proliferate in host cells，mainly including enterobactin，yersiniabactin，aerobactin，and salmochelin.A multi-drug resistant K.pneumoniae ST37 KP200 was isolated from the liver of sick pigs.This study analyzed the evolutionary relationship and genetic diversity of si-derophores of KP200 and 160 K.pneumoniae ST37 strains from NCBI with bioinformatics software.The single-copy core genes analysis results show that KP200 and a Chinese K.pneumoniae of human origin locate in the same clade with similarity of 99.8%.Siderophores analysis shows that all ST37 strains carry enterobactin entABCEF and fepABC.KP200 and other 15 K.pneumoniae strains carry aerobactin transporter gene iutA.The nucleotide homo-logy of 16 iutA gene sequences is 73.49%～100%.Compared with the iutA nucleotide sequence carried by the hypervirulent K.pneumoniae NTUH-K2044，it finds that the iutA nucleotide carried by KP200 results in two amino acid substitutions due to two base mutations： Leu is replaced by Phe and Val is replaced by Leu.This study provides basis for studying the evolution and virulence of K.pneumoniae ST37.

Key words: drug-resistant pathogens, Klebsiella pneumoniae, siderophores, evolutionary relationship, genetic diversity