Isolation and genomic analysis of temperate phage 5W targeting multidrug-resistant Acinetobacter baumannii.

Temperate phages are potential therapeutic agents, but only a few temperate phages infecting multidrug-resistant Acinetobacter baumannii have been identified. In this study, we isolated 5W, a temperate phage that infects multidrug-resistant A. baumannii, from pond water using the enrichment method. A member of the Siphoviridae family, 5W has a narrow host range and infected only four of 19 A. baumannii clinical isolates. It exhibited rapid adsorption (> 90% in 6 min), a latency period of 20 min, and a burst size of ~ 180 plaque-forming units (PFU/cell). 5W contains a linear double-stranded DNA (dsDNA) genome of 43,032 bp with a GC content of 39.85%. The 5W genome contains 61 open reading frames, including lysogen-forming genes, but lacks any known virulence and antibiotic resistance genes. The lysin of 5W is an N-acetyl-β-D-muramidase belonging to the GH_108 family. The α-helical structure and highly positively charged amino acids in the C-terminal region indicate potential antibacterial activity against A. baumannii, and the M/S subunits of the restriction endonuclease are inserted into the lysogenic gene cluster. Comparative genome analysis revealed high similarity with two different prophages in A. baumannii ABCR01, suggesting that 5W may be derived from recombination of other prophages.