期刊
JOURNAL OF DAIRY SCIENCE
卷 103, 期 4, 页码 3493-3504出版社
ELSEVIER SCIENCE INC
DOI: 10.3168/jds.2019-17458
关键词
bovine mastitis; Klebsiella pneumoniae; bovine mammary epithelial cells (bMEC); apoptosis; inflammation
资金
- Beijing Municipal Natural Science Foundation (Beijing, China) [6192013]
- National Key R&D Project (Beijing, China) [2016YFD0501203]
- National Natural Science Foundation of China (Beijing, China) [31772813, 31572587, 31660730, 31550110200]
- High-end Foreign Experts Recruitment Program (Beijing, China) [GDT20171100013]
Klebsiella pneumoniae, a common cause of clinical mastitis (CM) in dairy cows, can cause severe clinical symptoms. However, its pathogenicity in the bovine mammary gland is not well understood. Our objectives were to establish an in vitro infection model of K. pneumoniae on bovine mammary epithelial cells (bMEC) to assess (1) cytopathogenicity (adhesive and invasive ability, damage and apoptosis, pro-inflammatory effects) of K. pneumoniae on bMEC and (2) the role of hypermucoviscous (HMV) phenotype on cytopathogenicity. Two K. pneumoniae isolates from CM cows, 1 HMV and 1 non-HMV, were used to infect bMEC. Adhesion and invasion ability, release of lactate dehydrogenase (LDH), ultrastructural morphology, apoptosis, transcriptional expression of pro-inflammatory genes and production of pro-inflammatory cytokines were characterized at various intervals. Both K. pneumoniae isolates rapidly adhered to and invaded bMEC within 1 h post infection (pi), causing ultrastructural damage (swelling of mitochondria and vesicle formation on cell surface) after 3 h pi and apoptotic death after 9 h pi. In addition, K. pneumoniae promoted transcriptional expression of pro-inflammatory genes IL-6, IL-8, IL-1 beta, and tumor necrosis factor (TNF)-alpha and production of IL-8, IL-1 beta, and TNF-alpha cytokines. Compared with non-HMV K. pneumoniae, the HMV isolate had lower adhesive and invasive abilities but caused more serious cellular damage. In conclusion, K. pneumoniae was cytopathogenic on bMEC and induced a pro-inflammatory response; however, the HMV phenotype did not have a key role in pathogenicity. Therefore, more attention should be paid to milk loss, and targeted prevention and treatment strategies should be implemented in Klebsiella mastitis episodes.
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