中文摘要：

【目的】噬菌体具有防控耐药性病原菌的抗菌应用潜力,但是有些病原菌噬菌体的获得非常困难,研究发现大多数病原菌存在前噬菌体（Prophage）,且由前噬菌体编码的裂解酶（Endolysin）具有良好的抗菌应用前景,本研究将挖掘猪链球菌前噬菌体及其编码的裂解酶。【方法】通过对Gen Bank中登录的数株猪链球菌前噬菌体裂解酶的基因信息分析,挖掘出一株猪链球菌7型菌株前噬菌体编码的裂解酶,研究其生物学活性。以猪链球菌7型菌株7917的基因组为模板,采用PCR技术扩增获得裂解酶基因ly7917,将其克隆至质粒p ET28a（＋）并转化大肠杆菌DH5α细胞,挑选基因序列正确的阳性克隆、抽提质粒、转化表达菌株大肠杆菌BL21,经IPTG诱导可高效表达裂解酶Ly7917。【结果】平板裂解试验结果显示Ly7917具有高效裂菌活性,能够裂解猪链球菌2型高致病力菌株HA9801;浊度递减试验结果显示该裂解酶能够高效裂解猪链球菌2型、7型、9型和马链球菌兽疫亚种参考株、金黄色葡萄球菌（包括耐甲氧西林金黄色葡萄球菌）等多种革兰氏阳性菌。【结论】基于前噬菌体挖掘的裂解酶Ly7917,具有高效广谱裂菌活性,为临床上利用裂解酶治疗耐药菌的混合感染提供了可能。

英文摘要：

[Objective] In recent years, there has been an increasing worldwide prevalence of bacterial resistance to a wide range of antibiotics, resulting in a focus of research interest in bacteriophage. Unfortunately, Streptococcus suis（SS） bacteriophage is not easy to isolate, and the endolysin encoded by phage has been examined as a potential agent for SS control. [Methods] In this study, based on the analysis of genomic information of several Streptococcus suis deposited in Gen Bank, we mined and analyzed one endolysin named Ly7917 encoded by a prophage harbored in Streptococcus suis serotype 7（SS7） genome. The ly7917 gene was amplified by PCR using bacterial genome purified from a SS7 strain 7917 as template and then inserted into the p ET28a（＋） plasmid. The recombinant plasmid p ET28a（＋）-ly7917 was transformed into Escherichia coli DH5α, the sequencing of positive colony showed 100% homology with the target gene. The recombinant plasmid was then transformed into E. coli BL21 and induced with IPTG for expression. [Results] The result of plate analysis showed that Ly7917 has highly activity and can lysis Streptococcus suis serotype 2 strain HA9801. In addition, bacterial turbidity test showed that Streptococcus suis serotype 7, serotype 9, most of serotype 2 strains, Streptococcus equi subsp. zooepidemicus strain, Staphylococcus aureus（including Methicillin-resistant Staphylococcus aureus） were highly sensitive to Ly7917. [Conclusion] Effective and broad-spectrum characteristics of Ly7917 mined from prophage brings hope for mixed infection in clinical as an effective therapeutic.