摘要

       抗药性基因（ARGs）在包括鲍曼不动杆菌在内的革兰氏阴性病原体中的传播主要是通过可转移质粒介导的，然而ARGs经常整合到染色体中。ARGs是如何水平地结合到鲍曼杆菌的染色体上的，以及它是否是ARGs进一步扩散的一个原因，目前尚不清楚。在这里，我们证明了细胞间原噬菌体介导的ARGs在鲍曼杆菌中的无直接细胞间相互作用转移。我们从一株多重耐药鲍曼杆菌NU-60菌株的培养上清液中制备了含有细胞外DNA（eDNA）成分的ARG，并暴露了一株对抗生素敏感的鲍曼杆菌ATCC 17978对eDNA组分产生应变。抗药性（AR）A.baumani-ATCC 17978衍生物通过同源重组，从MDR A.baumani染色体的分散位点及其周围区域获得各种ARGs，ARGs包括armA（氨基糖苷类耐药）、bla TEM-1（β-内酰胺类耐药），tet（B）（四环素抗性）和gyrA-81L（萘啶酸抗性）基因。值得注意的是，产生抗药性的eDNAs被包裹在由噬菌体颗粒组成的特定衣壳蛋白中，从而保护eDNAs免受洗涤剂和DNase处理。含有ARGs的噬菌体很可能从MDR-A.baumani释放到胞外空间，从而将ARGs转化为A.baumani，导致受体获得AR特性。我们的结论是，噬菌体能够携带鲍曼杆菌基因组DNA的随机片段的普遍转导，使得鲍曼杆菌菌株之间的染色体ARGs能够有效地进行细胞间转移，而无需直接的细胞-细胞相互作用。

         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), bla _TEM-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/