Mastitis affects cows in all regions of the world and Escherichia coli (E. coli) is by far the most common reason of mastitis. Now antibiotic therapy is still the preferred approach of treating mastitis. However, antibiotic usage is easy to lead to antibiotic resistance. There is an urgent need for developing efficacious alternative antimicrobials. Pheromonicin-NM (PMC-NM) is a new engineered bactericidal peptide consisting of colicin Ia and an anti-porin A antibody mimetic. It can lead to the dissipation of cellular energy and therefore kill the bacteria rapidly. The aim of the present study was to investigate the comparative effects of PMC-NM and antibiotic ceftiofur on antibacterial and innate immune responses of bovine mammary epithelial cells (BMEC) to E. coli infection. We found that E. coli growth was inhibited by PMC-NM from 0.5 h after treatment and was completely inhibited at 3 h, indicating a rapid antibacterial activity for PMC-NM. The mRNA expression of TLR2, IL-1β, IL-8, lactoferrin, LAP, TAP and DEFB1 was increased by PMC-NM treatment at 2 h after E. coli infection, suggesting the enhanced inflammatory responses induced by PMC-NM contribute to pathogens clearance at early phase. By contrast, in E. coli-infected BMECs, ceftiofur treatment upregulated TLR2 and NOD2 levels at 12 h, and extremely elevated transcription levels of TNF-α, IL-1β, IL-8, lactoferrin, LAP, TAP, BNBD5, DEFB1 at 6 h. The excessive expression of these genes at later phase can induce uncontrolled inflammatory responses and finally cause damage. Taken together, PMC-NM might be used as an ideal antibacterial agent against E. coli mastitis.

乳腺炎影响世界所有地区的母牛，而大肠杆菌（E. coli）是迄今为止乳腺炎的最常见原因。现在，抗生素疗法仍然是治疗乳腺炎的首选方法。但是，抗生素的使用很容易导致抗生素耐药性。迫切需要开发有效的替代抗菌剂。信息素-NM（PMC-NM）是一种新型工程菌肽，由大肠菌素Ia和抗孔蛋白A抗体模拟物组成。它可以导致细胞能量的耗散，从而迅速杀死细菌。本研究的目的是研究PMC-NM和抗生素头孢噻呋对牛乳腺上皮细胞（BMEC）对E的抗菌和先天免疫应答的比较作用。大肠杆菌感染。我们发现，大肠杆菌的生长从处理后0.5小时起就被PMC-NM抑制，并在3小时时被完全抑制，表明对PMC-NM具有快速的抗菌活性。大肠杆菌感染后2 h PMC-NM处理可增加TLR2，IL-1β，IL-8，乳铁蛋白，LAP，TAP和DEFB1的mRNA表达，提示PMC-NM诱导的炎症反应增强，可引起病原体早期清除。相比之下，在大肠杆菌中感染的BMEC，头孢噻呋治疗在6 h时上调了TLR2和NOD2水平，并且在6 h时TNF-α，IL-1β，IL-8，乳铁蛋白，LAP，TAP，BNBD5，DEFB1的转录水平大大升高。这些基因在后期的过度表达会诱导不受控制的炎症反应，并最终造成损害。两者合计，PMC-NM可用作抗大肠杆菌乳腺炎的理想抗菌剂。