| Acinetobacter baumannii (A. baumannii) is a species of non-fermentative, non-motile,catalase-positive, gram-negative bacteria. These bacteria are found widely in soil, water,sewage, and many healthcare environments, and can cause severe pneumonia and infectionsof the urinary tract, bloodstream and other parts of the body. A. baumannii was susceptibleto most antibiotics in the1970s; however, most clinical A. baumannii strains isolated todayare increasingly multi-drug and pan-drug-resistant. The rapid development of resistance toantibiotics involves the acquisition of plasmids, transposons, or integrons carrying clusters ofgenes encoding resistance to several antibiotic families at the same time. As a result, themanagement of A. baumannii infections has become an urgent problem; we need to findalternative tools to combat such infections. Phage therapy may be a useful strategy in fightingthis type of bacterial infection.Over recent decades, a growing body of literature has validated the use of phages fortherapy and prophylaxis in the war against drug-resistant bacteria. Animal tests of phagetherapy have been designed for the treatment of various bacterial infections, and many lyticphages have been isolated and tested. In2011the Food and Drug Administration of USAapproved a mixture of bacteriophages as a food additive to protect people from foodbornebacterial diseases.Recently, we have isolated strain AB1of A. baumannii from a burn patient, and found itwas resistant to all the common antibiotics. Later, we have isolated a lytic bacteriophage ofAB1, Abp1, from the hospital sewage. In this study, we present the characterization andgenome sequence of Abp1, the data fundamental for its potential use in phage therapy. Themain contents and results are as followings1. Abp1has an icosahedral head about55nm in diameter and a short tail of around15nm in length. These morphological features suggest that the bacteriophage Abp1belongs to the Podoviridae virus family.2. Abp1genome can be digested by Dra I, Spe I, Nde I, and Pst I, so the genome ofAbp1consists of dsDNA. Based on the digestion profiles, the genome size was determined asapproximately40kb. Purified phage particles were subjected to SDS-PAGE, and proteomicpatterns were obtained after Coomassie Blue G-250staining and de-staining. One majorprotein band and9minor protein bands were observed on the gel.The group with a MOI of10-3generated most phage progeny, after a latent phase of10minutes, Abp1phage burst outat15minutes after infection. The plateau phase was reached at approximately40minutes.The burst size of the phage was350PFU/mL of infected cells3. The general characterization of Abp1genome was done by Huada. The final assemblyyielded a42185bp (G+C content,39.15%) linear double-stranded DNA. A total of141ORFslarger than100bp were found in the Abp1genome using ORF Finder;54putative genes wereidentified among these ORFs. The average length of a gene was about722bp, and theaverage gene density,1.29genes per1000bp.92.5%of the whole genome was used.5. Among the54putative genes,26were functionally known, leaving28unknownputative genes. We found10structural protein genes; this was confirmed by SDS-PAGE.Four HNH endonuclease genes were also identified; the HNH endonucleases belong to thehoming endonuclease family which confers the mobility or duplication of their coding andflanking sequences by a recombination-based process known as homing. Furthermore, DNAmaturase A, DNA helicase, DNA ligase, DNA exonuclease, DNA endonuclease VII, DNApolymerase, RNA polymerase, and dNMP kinase were identified by BLASTp program.Abp1should belong to phiKMV-like virus family of T7group.The genome data of phage Abp1has been deposited in GenBank under the accession No.JX658790... |
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