Table_2_Genomic and Proteomic Characterizations of Sfin-1, a Novel Lytic Phage Infecting Multidrug-Resistant Shigella spp. and Escherichia coli C.DOCX

Shigellosis is a public health threat in developed as well as developing countries like “India.” While antibiotic therapy is the mainstay of treatment for shigellosis, current emergence of multidrug-resistant strains of Shigella spp. has posed the problem more challenging. Lytic bacteriophages which destroy antibiotic resistant Shigella spp. have great potential in this context and hence their identification and detailed characterization is necessary. In this study we presented the isolation and a detailed characterization of a novel bacteriophage Sfin-1, which shows potent lytic activity against multidrug-resistant isolates of Shigella flexneri, Shigella dysenteriae, Shigella sonnei obtained from clinical specimens from shigellosis patients. It is also active against Escherichia coli C. The purified phage is lytic in nature, exhibited absorption within 5–10 min, a latent period of 5–20 min and burst size of ∼28 to ∼146 PFU/cell. The isolated phage shows stability in a broad pH range and survives an hour at 50°C. Genome sequencing and phylogenetic analyses showed that Sfin-1 is a novel bacteriophage, which is very closely related to T1-like phages (89.59% identity with Escherichia virus T1). In silico analysis indicates that Sfin-1 genome consists of double stranded linear DNA of 50,403 bp (GC content of 45.2%) encoding 82 potential coding sequences, several potential promoters and transcriptional terminators. Under electron microscopy, Sfin-1 shows morphology characteristics of the family Siphoviridae with an isometric head (61 nm) and a non-contractile tail (155 nm). This is most likely the first report of a lytic bacteriophage that is active against three of the most virulent multidrug-resistant Shigella species and therefore might have a potential role in phage therapy of patients infected with these organisms.

志贺菌病（Shigellosis）在发达国家与包括印度在内的发展中国家均构成公共卫生威胁。尽管抗生素治疗是志贺菌病的主流治疗手段，但当前志贺菌属（Shigella spp.）多重耐药菌株的出现，使得治疗难题愈发严峻。能够裂解抗生素耐药性志贺菌属菌株的裂解性噬菌体，在此背景下具备极大应用潜力，因此对其进行鉴定与详细表征至关重要。本研究成功分离得到一株新型噬菌体Sfin-1，并对其开展了全面细致的表征：该噬菌体对从志贺菌病患者临床标本中分离得到的福氏志贺菌（Shigella flexneri）、痢疾志贺菌（Shigella dysenteriae）、宋内志贺菌（Shigella sonnei）的多重耐药分离株均展现出强效裂解活性，同时对大肠杆菌C（Escherichia coli C）亦具有抗菌活性。纯化获得的噬菌体为裂解型，吸附周期为5~10分钟，潜伏期为5~20分钟，裂解量约为28~146 PFU/细胞。该分离噬菌体在宽泛的pH值范围内均能保持稳定，且在50℃条件下可存活1小时。基因组测序与系统发育分析结果显示，Sfin-1为一株新型噬菌体，与T1样噬菌体（T1-like phages）亲缘关系极为密切，与大肠杆菌病毒T1（Escherichia virus T1）的序列同源性达89.59%。计算机模拟（in silico）分析表明，Sfin-1的基因组为双链线性DNA，全长50403 bp，GC含量为45.2%，共编码82个潜在编码序列，以及若干潜在启动子与转录终止子。电子显微镜观察结果显示，Sfin-1具备长尾噬菌体科（Siphoviridae）的典型形态特征：呈等轴对称头部（直径61 nm），带有非收缩性尾部（长度155 nm）。本研究大概率是首次报道针对三种高毒力多重耐药志贺菌属均具有活性的裂解性噬菌体，因此其在上述病原体感染患者的噬菌体治疗领域具备潜在应用价值。