一株嗜麦芽窄食单胞菌裂解性噬菌体的分离及生物学特性

Isolation and biological characterization of a novel virulent phage targeting Stenotrophomnas maltophilia

摘要:

【背景】嗜麦芽窄食单胞菌是一种广泛存在于医院和自然环境中的条件致病菌，其分离率与耐药率逐年增加。噬菌体是一类能特异性感染并杀灭细菌的病毒。【目的】分离一株新型嗜麦芽窄食单胞菌噬菌体，为临床嗜麦芽窄食单胞菌感染及防控提供补充手段。【方法】以临床分离的嗜麦芽窄食单胞菌为宿主菌，用点板法从医院污水中分离鉴定噬菌体；用双层平板法测定噬菌体效价及一步生长曲线等生物学特性；用透射电镜观察噬菌体形态；提取噬菌体基因组DNA进行全基因组测序，拼接噬菌体基因组并进行注释。【结果】分离到一株嗜麦芽窄食单胞菌裂解性噬菌体，命名为vB_SmaS_P11。该噬菌体感染宿主菌的潜伏期小于5 min，快速增殖60 min后达到平稳期，暴发量为100 PFU/cell。透射电镜观察该噬菌体为长尾噬菌体，具有典型的二十面体头和不可收缩的尾部。基因组测序结果表明，该噬菌体基因组全长44 600 bp，GC含量为63.7%，无抗生素耐受基因、毒力基因和tRNA，与NCBI数据库中所有已知嗜麦芽窄食单胞菌噬菌体相比同源性很低。基因组注释显示该噬菌体含有66个开放阅读框(open reading frame，ORF)，其中25个ORF预测为有功能的蛋白，15个ORF是未知功能的假定蛋白，26个ORF比对结果显示没有相似的序列。序列比对与系统发育分析表明，该噬菌体属于有尾噬菌体目(Caudovirales)长尾噬菌体科(Siphoviridae)。【结论】本研究分离鉴定到一株裂解性强、相似性低的嗜麦芽窄食单胞菌噬菌体，该噬菌体有望用于抗生素耐受嗜麦芽窄食单胞菌感染控制。

Abstract:

[Background] Stenotrophomonas maltophilia is an opportunistic pathogen that exists widely in hospitals and environments,with intrinsic antibiotic resistance.[Objective] This study aims to isolate virulent phages to provide an alternative therapeutic method for S.maltophilia infection.[Methods] A phage was isolated from hospital sewage with a clinical strain of S.maltophilia as the host.The phage genome was sequenced on Illumina platform and its morphology was observed with transmission electron microscopy.The one-step growth curve was established by double-layer plate method.[Results] The isolated phage vB_SmaS_P11 had an icosahedral head and a long tail,belonging to Siphoviridae of Caudovirales.The genome of the phage had a length of 44 600 bp and the G+C content of 63.7%,encoding 66 open reading frames (ORFs),with no tRNA,virulence genes or resistance-related regions.The phage vB_SmaS_P11 was able to lyse 7 strains among 18 clinical isolates of S.maltophilia.The one-step growth curve showed that the strain had the latent time less than 5 min,the lysis period of about 60 min,and the burst size of 100 plaque forming units per cell,which indicated high virulence.[Conclusion] The isolated phage vB_SmaS_P11 is a novel virulent phage targeting S.maltophilia,which provides a candidate phage for treating S.maltophilia infection in the future.