title: A method for generation phage cocktail with great therapeutic potential.
abstract: BACKGROUND
  Bacteriophage could be an alternative to conventional antibiotic therapy against multidrug-resistant bacteria. However, the emergence of resistant variants after phage treatment limited its therapeutic application.
  
  
  RESULTS
  In this study, an approach, named "Step-by-Step" (SBS), has been established. This method takes advantage of the occurrence of phage-resistant bacteria variants and ensures that phages lytic for wild-type strain and its phage-resistant variants are selected. A phage cocktail lytic for Klebsiella pneumoniae was established by the SBS method. This phage cocktail consisted of three phages (GH-K1, GH-K2 and GH-K3) which have different but overlapping host strains. Several phage-resistant variants of Klebsiella pneumoniae were isolated after different phages treatments. The virulence of these variants was much weaker [minimal lethal doses (MLD)>1.3×10(9) cfu/mouse] than that of wild-type K7 countpart (MLD = 2.5×10(3) cfu/mouse). Compared with any single phage, the phage cocktail significantly reduced the mutation frequency of Klebsiella pneumoniae and effectively rescued Klebsiella pneumoniae bacteremia in a murine K7 strain challenge model. The minimal protective dose (MPD) of the phage cocktail which was sufficient to protect bacteremic mice from lethal K7 infection was only 3.0×10(4) pfu, significantly smaller (p<0.01) than that of single monophage. Moreover, a delayed administration of this phage cocktail was still effective in protection against K7 challenge.
  
  
  CONCLUSIONS
  Our data showed that the phage cocktail was more effective in reducing bacterial mutation frequency and in the rescue of murine bacteremia than monophage suggesting that phage cocktail established by SBS method has great therapeutic potential for multidrug-resistant bacteria infection.
authors.affiliation: College of Animal Science and Veterinary Medicine, Jilin University, Changchun, People's Republic of China.
authors.forename: Jingmin
authors.initials: J
authors.lastname: Gu
authors.forename: Xiaohe
authors.initials: X
authors.lastname: Liu
authors.forename: Yue
authors.initials: Y
authors.lastname: Li
authors.forename: Wenyu
authors.initials: W
authors.lastname: Han
authors.forename: Liancheng
authors.initials: L
authors.lastname: Lei
authors.forename: Yongjun
authors.initials: Y
authors.lastname: Yang
authors.forename: Honglei
authors.initials: H
authors.lastname: Zhao
authors.forename: Yu
authors.initials: Y
authors.lastname: Gao
authors.forename: Jun
authors.initials: J
authors.lastname: Song
authors.forename: Rong
authors.initials: R
authors.lastname: Lu
authors.forename: Changjiang
authors.initials: C
authors.lastname: Sun
authors.forename: Xin
authors.initials: X
authors.lastname: Feng
mesh_terms: D000818:Animals; D001424:Bacterial Infections / Q000628:therapy*; D001435:Bacteriophages / Q000378:metabolism*; D015195:Drug Design; D024881:Drug Resistance, Bacterial; D005260:Female; D014644:Genetic Variation; D007710:Klebsiella Infections / Q000628:therapy; D007711:Klebsiella pneumoniae / Q000235:genetics; D051379:Mice; D008807:Mice, Inbred BALB C; D008826:Microbial Sensitivity Tests; D008854:Microscopy, Electron; D009154:Mutation; D059645:Mutation Rate; D013234:Stem Cells