Lai Meng-Jiun, Chang Kai-Chih, Huang Shiuan-Wen, Luo Cheng-Hung, Chiou Pei-Yu, Wu Chao-Chuan, Lin Nien-Tsung
Department of Laboratory Medicine and Biotechnology, Tzu Chi University, Hualien, Taiwan.
Master Program in Microbiology and Immunology, School of Medicine, Tzu Chi University, Hualien, Taiwan.
PLoS One. 2016 Apr 14;11(4):e0153361. doi: 10.1371/journal.pone.0153361. eCollection 2016.
Acinetobacter baumannii is a non-fermenting, gram-negative bacterium. In recent years, the frequency of A. baumannii infections has continued to increase, and multidrug-resistant strains are emerging in hospitalized patients. Therefore, as therapeutic options become limited, the potential of phages as natural antimicrobial agents to control infections is worth reconsidering. In our previous study, we isolated ten virulent double-stranded DNA A. baumannii phages, ϕAB1-9 and ϕAB11, and found that each has a narrow host range. Many reports indicate that receptor-binding protein of phage mediates host recognition; however, understanding of the specific interactions between A. baumannii and phages remains very limited. In this study, host determinants of A. baumannii phages were investigated. Sequence comparison of ϕAB6 and ϕAB1 revealed high degrees of conservation among their genes except the tail fiber protein (ORF41 in ϕAB1 and ORF40 in ϕAB6). Furthermore, we found that ORF40ϕAB6 has polysaccharide depolymerase activity capable of hydrolyzing the A. baumannii exopolysaccharide and is a component of the phage tail apparatus determining host specificity. Thus, the lytic phages and their associated depolymerase not only have potential as alternative therapeutic agents for treating A. baumannii infections but also provide useful and highly specific tools for studying host strain exopolysaccharides and producing glycoconjugate vaccines.
鲍曼不动杆菌是一种非发酵革兰氏阴性菌。近年来，鲍曼不动杆菌感染的发生率持续上升，住院患者中出现了多重耐药菌株。因此，随着治疗选择变得有限，噬菌体作为控制感染的天然抗菌剂的潜力值得重新审视。在我们之前的研究中，我们分离出了十种毒性双链DNA鲍曼不动杆菌噬菌体，ϕAB1 - 9和ϕAB11，并发现它们各自的宿主范围较窄。许多报告表明噬菌体的受体结合蛋白介导宿主识别；然而，对鲍曼不动杆菌与噬菌体之间具体相互作用的了解仍然非常有限。在本研究中，对鲍曼不动杆菌噬菌体的宿主决定因素进行了研究。ϕAB6和ϕAB1的序列比较显示，除尾丝蛋白外（ϕAB1中的ORF41和ϕAB6中的ORF40），它们的基因之间具有高度保守性。此外，我们发现ORF40ϕAB6具有能够水解鲍曼不动杆菌胞外多糖的多糖解聚酶活性，并且是决定宿主特异性的噬菌体尾部装置的一个组成部分。因此，裂解性噬菌体及其相关的解聚酶不仅具有作为治疗鲍曼不动杆菌感染的替代治疗剂的潜力，而且为研究宿主菌株胞外多糖和生产糖缀合物疫苗提供了有用且高度特异的工具。
