基于全基因组学的国内5省份奶牛乳腺炎肺炎克雷伯菌分子特征及多样性分析OA

Bovine mastitis is regarded as one of the major diseases affecting dairy industry in China,and Klebsiella pneumoniae(Kp)is recognized as one of its key pathogens.In order to investigate the genetic and molecular epidemiological characteristics of Kp,214 strains isolated from mastitic milk samples collected from five provinces including Shandong,Hebei,Heilongjiang,Henan and Hubei were analyzed for whole-genome diversity,phylogenetic relationships,antimicrobial resistance genes,plasmid types and virulence features.Multi-locus sequence typing(MLST)revealed a polyclonal population structure with distinct regional differences in predominant sequence types(STs).The dominant STs in Shandong,Hebei,Heilongjiang and Henan were ST2324,ST43,ST7514 and ST107,respectively,but more diverse in Hubei,comprising 11 STs including ST234,ST661,ST4452 and others.Phylogenetic and serotype analyses showed that the isolates were classified into four clades(Clades Ⅰ-Ⅳ),including 30 serotypes such as K34,K30,K11 and K48.Antimicrobial resistance gene analysis indicated that 85 resistance genes belonging to 10 classes of antimicrobial agents were carried by the isolates,and efflux pump genes oqxA and oqxB were harbored by all the isolates.Plasmid analysis showed that 27 types of plasmids were carried by the isolates,dominated by IncFIB(K)_1_Kpn3(89.25％),while IncR,IncHI1 and IncHI2 plasmids were detected from some isolates.Virulence gene analysis showed that genes associated with adhesion and iron acquisition were widely distributed in most isolates,but hypervirulence-associated gene clusters were rarely detected.In conclusion,polyclonal diversity and regional variation were observed in Kp isolates from bovine mastitis,with diverse antimicrobial resistance and virulence genes as well as complex types of plasmids.Future prevention and control of bovine mastitis and prudent use of antimicrobials in dairy production were supported by the data obtained from the study.