The susceptibility of Pseudomonas aeruginosa strains from cystic fibrosis patients to bacteriophages

PLoS One. 2013 Apr 24;8(4):e60575. doi: 10.1371/journal.pone.0060575. Print 2013.

Abstract

Phage therapy may become a complement to antibiotics in the treatment of chronic Pseudomonas aeruginosa infection. To design efficient therapeutic cocktails, the genetic diversity of the species and the spectrum of susceptibility to bacteriophages must be investigated. Bacterial strains showing high levels of phage resistance need to be identified in order to decipher the underlying mechanisms. Here we have selected genetically diverse P. aeruginosa strains from cystic fibrosis patients and tested their susceptibility to a large collection of phages. Based on plaque morphology and restriction profiles, six different phages were purified from "pyophage", a commercial cocktail directed against five different bacterial species, including P. aeruginosa. Characterization of these phages by electron microscopy and sequencing of genome fragments showed that they belong to 4 different genera. Among 47 P. aeruginosa strains, 13 were not lysed by any of the isolated phages individually or by pyophage. We isolated two new phages that could lyse some of these strains, and their genomes were sequenced. The presence/absence of a CRISPR-Cas system (Clustered Regularly Interspaced Short Palindromic Repeats and Crisper associated genes) was investigated to evaluate the role of the system in phage resistance. Altogether, the results show that some P. aeruginosa strains cannot support the growth of any of the tested phages belonging to 5 different genera, and suggest that the CRISPR-Cas system is not a major defence mechanism against these lytic phages.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacteriophages / isolation & purification
  • Bacteriophages / physiology*
  • Bacteriophages / ultrastructure
  • CRISPR-Cas Systems / genetics
  • Clustered Regularly Interspaced Short Palindromic Repeats
  • Cystic Fibrosis / microbiology*
  • Gene Order
  • Genome, Viral / genetics
  • Humans
  • Pseudomonas Infections / microbiology
  • Pseudomonas aeruginosa / genetics
  • Pseudomonas aeruginosa / isolation & purification
  • Pseudomonas aeruginosa / metabolism
  • Pseudomonas aeruginosa / virology*
  • Viral Plaque Assay

Grant support

This study was performed with the financial support of the association Vaincre La Mucoviscidose (Grant N° 2010/IC1020). The development of tools for the surveillance of bacterial pathogens is supported by the French Direction Générale de l'Armement (DGA). CE holds a fellowship of Agence Universitaire de la Francophonie. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.