摘要

       抗菌素耐药基因 (ARG) 在革兰氏阴性病原体（包括鲍曼不动杆菌）中的传播主要由可转移质粒介导；然而，ARGs 经常被整合到它的染色体中。 ARG 如何水平整合到鲍曼不动杆菌的染色体中，以及它是否作为 ARG 进一步传播的原因，仍然未知。在这里，我们证明了在鲍曼不动杆菌中细胞间原噬菌体介导的染色体 ARG 转移，而没有直接的细胞 - 细胞相互作用。我们从多重耐药 (MDR) 鲍曼不动杆菌 NU-60 菌株的培养上清液中制备了携带 ARG 的细胞外 DNA (eDNA) 成分，并将抗菌敏感 (AS) 鲍曼不动杆菌 ATCC 17978 菌株暴露于 eDNA 成分。抗微生物 (AR) 鲍曼不动杆菌 ATCC 17978 衍生物似乎获得了各种 ARG，这些 ARG 源自 MDR 鲍曼不动杆菌染色体的分散位点及其周围区域，通过同源重组，ARG 包括 armA（氨基糖苷类抗性） 、blaTEM-1（β-内酰胺抗性）、tet(B)（四环素抗性）和 gyrA-81L（萘啶酸抗性）基因。值得注意的是，赋予抗菌素耐药性的 eDNA 被包裹在由噬菌体颗粒组成的特定衣壳蛋白中，从而保护 eDNA 免受洗涤剂和 DNase 的处理。含有 ARGs 的噬菌体很可能从 MDR 鲍曼不动杆菌释放到细胞外空间，从而将 ARGs 转化为 A.鲍曼不动杆菌，从而导致受体获得 AR 特性。我们得出结论，噬菌体能够携带随机片段的鲍曼不动杆菌基因组 DNA 的广义转导能够有效地在鲍曼不动杆菌菌株之间进行染色体 ARG 的细胞间转移，而无需直接的细胞间相互作用。

       The spread of antimicrobial resistance genes (ARGs) among Gram-negative pathogens, including Acinetobacter baumannii, is primarily mediated by transferable plasmids; however, ARGs are frequently integrated into its chromosome. How ARG gets horizontally incorporated into the chromosome of A. baumannii, and whether it functions as a cause for further spread of ARG, remains unknown. Here, we demonstrated intercellular prophage-mediated transfer of chromosomal ARGs without direct cell-cell interaction in A. baumannii. We prepared ARG-harboring extracellular DNA (eDNA) components from the culture supernatant of a multidrug-resistant (MDR) A. baumannii NU-60 strain and exposed an antimicrobial-susceptible (AS) A. baumannii ATCC 17978 strain to the eDNA components. The antimicrobial-resistant (AR) A. baumannii ATCC 17978 derivatives appeared to acquire various ARGs, originating from dispersed loci of the MDR A. baumannii chromosome, along with their surrounding regions, by homologous recombination, with the ARGs including armA (aminoglycoside resistance), blaTEM-1 (β-lactam resistance), tet(B) (tetracycline resistance), and gyrA-81L (nalidixic acid resistance) genes. Notably, the eDNAs conferring antimicrobial resistance were enveloped in specific capsid proteins consisting of phage particles, thereby protecting the eDNAs from detergent and DNase treatments. The phages containing ARGs were likely released into the extracellular space from MDR A. baumannii, thereby transducing ARGs into AS A. baumannii, resulting in the acquisition of AR properties by the recipient. We concluded that the generalized transduction, in which phages were capable of carrying random pieces of A. baumannii genomic DNAs, enabled efficacious intercellular transfer of chromosomal ARGs between A. baumannii strains without direct cell-cell interaction.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6658751/