title: Bacteriophage-resistant mutants in Yersinia pestis: identification of phage receptors and attenuation for mice.
abstract: BACKGROUND
  Bacteriophages specific for Yersinia pestis are routinely used for plague diagnostics and could be an alternative to antibiotics in case of drug-resistant plague. A major concern of bacteriophage therapy is the emergence of phage-resistant mutants. The use of phage cocktails can overcome this problem but only if the phages exploit different receptors. Some phage-resistant mutants lose virulence and therefore should not complicate bacteriophage therapy.
  
  
  RESULTS
  The purpose of this work was to identify Y. pestis phage receptors using site-directed mutagenesis and trans-complementation and to determine potential attenuation of phage-resistant mutants for mice. Six receptors for eight phages were found in different parts of the lipopolysaccharide (LPS) inner and outer core. The receptor for R phage was localized beyond the LPS core. Most spontaneous and defined phage-resistant mutants of Y. pestis were attenuated, showing increase in LD₅₀ and time to death. The loss of different LPS core biosynthesis enzymes resulted in the reduction of Y. pestis virulence and there was a correlation between the degree of core truncation and the impact on virulence. The yrbH and waaA mutants completely lost their virulence.
  
  
  CONCLUSIONS
  We identified Y. pestis receptors for eight bacteriophages. Nine phages together use at least seven different Y. pestis receptors that makes some of them promising for formulation of plague therapeutic cocktails. Most phage-resistant Y. pestis mutants become attenuated and thus should not pose a serious problem for bacteriophage therapy of plague. LPS is a critical virulence factor of Y. pestis.
authors: Division of Bacterial and Rickettsial Diseases, Department of Emerging Bacterial Infections, Walter Reed Army Institute of Research, Silver Spring, Maryland, United States of America. andrey.filippov@amedd.army.mil
authors: Andrey A
authors: AA
authors: Filippov
authors: Kirill V
authors: KV
authors: Sergueev
authors: Yunxiu
authors: Y
authors: He
authors: Xiao-Zhe
authors: XZ
authors: Huang
authors: Bryan T
authors: BT
authors: Gnade
authors: Allen J
authors: AJ
authors: Mueller
authors: Carmen M
authors: CM
authors: Fernandez-Prada
authors: Mikeljon P
authors: MP
authors: Nikolich
mesh_terms: D000818:Animals; D001435:Bacteriophages / Q000378:metabolism / Q000502:physiology*; D005260:Female; D008070:Lipopolysaccharides / Q000378:metabolism; D051379:Mice; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010930:Plague / Q000628:therapy / Q000821:virology; D021381:Protein Transport; D011991:Receptors, Virus / Q000235:genetics / Q000378:metabolism*; D013045:Species Specificity; D015010:Yersinia pestis / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity / Q000821:virology*
chemical_list: D008070:Lipopolysaccharides; D011991:Receptors, Virus