Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China.
Tianjin Key Laboratory of Agricultural Animal Breeding and Healthy Husbandry, College of Animal Science and Veterinary Medicine, Tianjin Agricultural University, Tianjin, China.
Front Cell Infect Microbiol. 2023 Sep 7;13:1253815. doi: 10.3389/fcimb.2023.1253815. eCollection 2023.
The inappropriate use of antibiotics has led to the emergence of multidrug-resistant strains. Bacteriophages (phages) have gained renewed attention as promising alternatives or supplements to antibiotics. In this study, a lytic avian pathogenic (APEC) phage designated as PEC9 was isolated and purified from chicken farm feces samples. The morphology, genomic information, optimal multiplicity of infection (MOI), one-step growth curve, thermal stability, pH stability, antibacterial ability and biofilm formation inhibition ability of the phage were determined. Subsequently, the therapeutic effects of the phages were investigated in the mice model. The results showed that PEC9 was a member of the siphovirus-like by electron microscopy observation. Biological characterization revealed that it could lyse two serotypes of , including O1 (9/20) and O2 (6/20). The optimal multiplicity of infection (MOI) of phage PEC9 was 0.1. Phage PEC9 had a latent period of 20 min and a burst period of 40 min, with an average burst size of 68 plaque-forming units (PFUs)/cell. It maintained good lytic activity at pH 3-11 and 4-50°C and could efficiently inhibit the bacterial planktonic cell growth and biofilm formation, and reduce bacterial counts within the biofilm, when the MOI was 0.01, 0.1, and 1, respectively. Whole-genome sequencing showed that PEC9 was a dsDNA virus with a genome of 44379 bp and GC content of 54.39%. The genome contains 56 putative ORFs and no toxin, virulence, or resistance-related genes were detected. Phylogenetic tree analysis showed that PEC9 is closely related to phages vB_EcoS_Zar3M, vB_EcoS_PTXU06, SECphi18, ZCEC10, and ZCEC11, but most of these phages exhibit different gene arrangement. The phage PEC9 could successfully protect mice against APEC infection, including improved survival rate, reduced bacterial loads, and organ lesions. To conclude, our results suggest that phage PEC9 may be a promising candidate that can be used as an alternative to antibiotics in the control of APEC infection.
抗生素的不当使用导致了多药耐药菌株的出现。噬菌体（phages）作为抗生素的替代品或补充品，重新引起了人们的关注。在这项研究中，从鸡场粪便样本中分离和纯化了一种溶菌性禽致病性（APEC）噬菌体，命名为 PEC9。测定了噬菌体的形态、基因组信息、最佳感染复数（MOI）、一步生长曲线、热稳定性、pH 稳定性、抗菌能力和生物膜形成抑制能力。随后，在小鼠模型中研究了噬菌体的治疗效果。结果表明，PEC9 通过电子显微镜观察属于类似丝状噬菌体的成员。生物学特性表明，它可以裂解两种血清型，包括 O1（9/20）和 O2（6/20）。噬菌体 PEC9 的最佳感染复数（MOI）为 0.1。噬菌体 PEC9 的潜伏期为 20 分钟，爆发期为 40 分钟，平均爆发大小为 68 个噬菌斑形成单位（PFU）/细胞。当 MOI 分别为 0.01、0.1 和 1 时，噬菌体 PEC9 在 pH 3-11 和 4-50°C 下保持良好的溶菌活性，能有效抑制浮游细胞生长和生物膜形成，并降低生物膜内的细菌计数。全基因组测序表明，PEC9 是一种双链 DNA 病毒，基因组大小为 44379 bp，GC 含量为 54.39%。基因组包含 56 个推定的 ORFs，未检测到毒素、毒力或耐药相关基因。系统发育树分析表明，PEC9 与噬菌体 vB_EcoS_Zar3M、vB_EcoS_PTXU06、SECphi18、ZCEC10 和 ZCEC11 密切相关，但这些噬菌体的基因排列大多不同。噬菌体 PEC9 能成功保护小鼠免受 APEC 感染，包括提高存活率、降低细菌负荷和器官损伤。综上所述，我们的研究结果表明，噬菌体 PEC9 可能是一种有前途的候选药物，可作为控制 APEC 感染的抗生素替代品。
