Abstract：
Non-aureus staphylococci (NAS) are an essential group of bacteria causing antimicrobial resistant intramammary infections in livestock, particularly dairy cows. Therefore, bacteriophages emerge as a potent bactericidal agent for NAS mastitis. This study aimed to obtain NAS-specific bacteriophages using bacterial strains isolated from cows with mastitis, subsequently evaluating their morphological, genomic, and lytic characteristics. Four distinct NAS bacteriophages were recovered from sewage or the environment of Chinese dairy farms; PT1-1, PT94, and PT1-9 were isolated using Staphylococcus chromogenes and PT1-4 using Staphylococcus gallinarum. Both PT1-1 (24/54, 44 %) and PT94 (28/54, 52 %) had broader lysis than PT1-4 (3/54, 6 %) and PT1-9 (10/54, 19 %), but PT1-4 and PT1-9 achieved cross-species lysis. All bacteriophages had a short latency period and good environmental tolerance, including surviving at pH=4-10 and at 30-60℃. Except for PT1-9, all bacteriophages had excellent bactericidal efficacy within 5 h of co-culture with host bacteria in vitro at various multiplicity of infection (MOIs). Based on whole genome sequencing, average nucleotide identity (ANI) analysis of PT1-1 and PT94 can be classified as the same species, consistent with whole-genome synteny analysis. Although motifs shared by the 4 bacteriophages differed little from those of other bacteriophages, a phylogenetic tree based on functional proteins indicated their novelty. Moreover, based on whole genome comparisons, we inferred that cross-species lysis of bacteriophage may be related to the presence of \"phage tail fiber.\" In conclusion 4 novel NAS bacteriophages were isolated; they had good biological properties and unique genomes, with potential for NAS mastitis therapy.
摘要：
非金黄色葡萄球菌（NAS）是导致家畜耐抗生素性乳房内感染的重要细菌，尤其是奶牛。因此,噬菌体是NAS乳腺炎的有效杀菌剂。本研究旨在使用从乳腺炎奶牛中分离的细菌菌株获得NAS特异性噬菌体，随后评估它们的形态，基因组，和裂解特性。从污水或中国奶牛场的环境中回收了四种不同的NAS噬菌体；使用色葡萄球菌分离PT1-1，PT94和PT1-9，使用鸡葡萄球菌分离PT1-4。PT1-1（24/54，44％）和PT94（28/54，52％）比PT1-4（3/54，6％）和PT1-9（10/54，19％）具有更广泛的裂解，但PT1-4和PT1-9实现了跨物种裂解。所有噬菌体潜伏期短，环境耐受性好，包括在pH=4-10和30-60℃下存活。除PT1-9外，所有噬菌体在各种感染复数（MOI）下与宿主细菌共培养5小时内都具有出色的杀菌效果。基于全基因组测序，PT1-1和PT94的平均核苷酸同一性（ANI）分析可以归类为同一物种，与全基因组同种关系分析一致。尽管4种噬菌体共有的基序与其他噬菌体的基序差异不大，基于功能蛋白质的系统发育树表明了它们的新颖性。此外，基于全基因组比较，我们推断噬菌体的跨物种裂解可能与“噬菌体尾纤维”的存在有关。“结论分离出4种新型NAS噬菌体；它们具有良好的生物学特性和独特的基因组，具有NAS乳腺炎治疗的潜力。
