Wang Jiayun, Li Jun, Ji Xing, Zhang Lili, Wang Ran, Wang Heng, He Tao
Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, College of Veterinary Medicine, Yangzhou University, Yangzhou, 225009, China.
Jiangsu Key Laboratory for Food Quality and Satety - State Key Laboratory Cultivation Base of Ministry of Science and Technology, Institute of Food Safety and Nutrition, Jiangsu Academy of Agricultural Sciences, Nanjing, 210040, China.
BMC Microbiol. 2025 Jul 3;25(1):407. doi: 10.1186/s12866-025-04147-5.
The bovine mastitis caused by Klebsiella pneumoniae (K. pneumoniae) infection, lead to high death rate and severe economic loss. Currently, the regional epidemiological characteristics of K. pneumoniae in China are still unclear, especially the surveillance data on prevalence of extended-spectrum β-lactamase (ESBL)-producing K. pneumoniae in the cow are still limited. In this study, the epidemiology of K. pneumoniae from mastitis-infected cows in large-scale dairy farms in China were investigated.
A total of 108 isolates of K. pneumoniae were isolated from 763 mastitis-associated milk samples collected from dairy farms in Jiangsu, Anhui, Hebei, Fujian, Guangdong, Shanxi and Zhejiang provinces in China. The whole genomes of 108 strains of K. pneumoniae were sequenced to identify their phylogenetic relationships, antimicrobial resistance and virulence genes. The antimicrobial susceptibility was determined by micro-broth dilution method according to the Clinical Laboratory and Standards Institute (CLSI) guidelines M100-S31.
The K. pneumoniae isolates were divided into 42 different sequence types (STs) and 43 K Locus (KL) types. No dominant ST and KL were identified in this study, reflecting the great genetic divergence in the K. pneumoniae population. While ST1049 and KL5 were relatively prevalent, potentially indicating a robust transmission capability. Among the 78 virulence genes identified, eight isolates carried the aerobactin-encoding gene cluster iucABCD/iutA (iuc), which might be hypervirulent strains. The K. pneumoniae isolates showed variable resistance levels to cefotaxime, ceftiofur, cephalexin, ceftazidime, meropenem, florfenicol, sulfamethoxazole, trimethoprim/sulfamethoxazole, amikacin, gentamicin, streptomycin and tetracycline, while sensitive to ciprofloxacin, polymyxin B or tigecycline. A total of 73 kinds of antimicrobial resistance (AMR) genes were identified, and 28 strains were determined to be ESBL-producing bacteria. The pKP83 plasmid 2, which carried bla and bla genes, was highly homological to three ESBL plasmids from human. The horizontal transfer potential of pKP83 plasmid 2 was further verified by conjugation to Escherichia coli J53 and K. pneumoniae K12016.
It is necessary to conduct the regular monitoring of the antibiotic resistance of clinical K. pneumoniae from bovine mastitis, in order to prevent and control the transmission of K. pneumoniae along the food chain.
肺炎克雷伯菌（K. pneumoniae）感染引起的牛乳腺炎，导致高死亡率和严重的经济损失。目前，中国肺炎克雷伯菌的区域流行病学特征仍不清楚，尤其是关于产超广谱β-内酰胺酶（ESBL）肺炎克雷伯菌在奶牛中流行情况的监测数据仍然有限。本研究对中国大型奶牛场中患乳腺炎奶牛的肺炎克雷伯菌流行病学进行了调查。
从中国江苏、安徽、河北、福建、广东、山西和浙江等省奶牛场采集的763份与乳腺炎相关的牛奶样本中，共分离出108株肺炎克雷伯菌。对108株肺炎克雷伯菌进行全基因组测序，以确定它们的系统发育关系、抗菌药物耐药性和毒力基因。根据临床实验室标准协会（CLSI）指南M100-S31，采用微量肉汤稀释法测定抗菌药物敏感性。
肺炎克雷伯菌分离株分为42种不同的序列类型（STs）和43种K位点（KL）类型。本研究未发现优势ST和KL，反映出肺炎克雷伯菌群体中存在较大的遗传差异。虽然ST1049和KL5相对普遍，可能表明其具有较强的传播能力。在鉴定出的78个毒力基因中，有8株携带编码气杆菌素的基因簇iucABCD/iutA（iuc），可能是高毒力菌株。肺炎克雷伯菌分离株对头孢噻肟、头孢噻呋、头孢氨苄、头孢他啶、美罗培南、氟苯尼考、磺胺甲恶唑、甲氧苄啶/磺胺甲恶唑、阿米卡星、庆大霉素、链霉素和四环素表现出不同程度的耐药性，而对环丙沙星、多粘菌素B或替加环素敏感。共鉴定出73种抗菌药物耐药（AMR）基因，确定28株为产ESBL细菌。携带bla和bla基因的pKP83质粒2与来自人类的三种ESBL质粒高度同源。通过与大肠杆菌J53和肺炎克雷伯菌K12016进行接合试验，进一步验证了pKP83质粒2的水平转移潜力。
有必要定期监测临床患牛乳腺炎肺炎克雷伯菌的抗生素耐药性，以防控肺炎克雷伯菌沿食物链传播。
