Abstract

BackgroundAs is true for many other antibiotic-resistant Gram-negative pathogens, members of the Burkholderia cepacia complex (BCC) are currently being assessed for their susceptibility to phage therapy as an antimicrobial treatment. The objective of this study was to perform genomic and limited functional characterization of the novel BCC phage JG068 (vB_BceP_JG068).ResultsJG068 is a podovirus that forms large, clear plaques on Burkholderia cenocepacia K56-2. Host range analysis indicates that this phage can infect environmental, clinical, and epidemic isolates of Burkholderia multivorans, B. cenocepacia, Burkholderia stabilis, and Burkholderia dolosa, likely through interaction with the host lipopolysaccharide as a receptor. The JG068 chromosome is 41,604 base pairs (bp) in length and is flanked by 216 bp short direct terminal repeats. Gene expression originates from both host and phage promoters and is in the forward direction for all 49 open reading frames. The genome sequence shows similarity to Ralstonia phage ϕRSB1, Caulobacter phage Cd1, and uncharacterized genetic loci of blood disease bacterium R229 and Burkholderia pseudomallei 1710b. CoreGenesUniqueGenes analysis indicates that JG068 belongs to the Autographivirinae subfamily and ϕKMV-like phages genus. Modules within the genome encode proteins involved in DNA-binding, morphogenesis, and lysis, but none associated with pathogenicity or lysogeny. Similar to the signal-arrest-release (SAR) endolysin of ϕKMV, inducible expression of the JG068 SAR endolysin causes lysis of Escherichia coli that is dependent on the presence of an N-terminal signal sequence. In an in vivo assay using the Galleria mellonella infection model, treatment of B. cenocepacia K56-2-infected larvae with JG068 results in a significant increase in larval survival.ConclusionsAs JG068 has a broad host range, does not encode virulence factors, is obligately lytic, and has activity against an epidemic B. cenocepacia strain in vivo, this phage is a highly promising candidate for BCC phage therapy development.

Highlights

  • As is true for many other antibiotic-resistant Gram-negative pathogens, members of the Burkholderia cepacia complex (BCC) are currently being assessed for their susceptibility to phage therapy as an antimicrobial treatment

  • The three susceptible B. cenocepacia strains and AU0158 have all been linked to epidemic spread among cystic fibrosis (CF) patients [19,21]

  • One of the greatest challenges in BCC phage therapy development is the identification of phages with a broad, clinically relevant host range that are free of virulence genes, obligately lytic, and active in vivo

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Summary

Introduction

As is true for many other antibiotic-resistant Gram-negative pathogens, members of the Burkholderia cepacia complex (BCC) are currently being assessed for their susceptibility to phage therapy as an antimicrobial treatment. The Burkholderia cepacia complex (BCC) is a group of antibiotic-resistant Gram-negative species that appear to be a promising target for phage therapy. These bacteria cause transmissible and potentially fatal opportunistic infections in cystic fibrosis (CF) and immunocompromised patients. Similar to P. aeruginosa, BCC bacteria are innately antibiotic-resistant owing to a variety of mechanisms (reviewed in [7]) Antibiotics such as meropenem, minocycline, and ceftazidime show partial efficacy against some clinical isolates, but the vast majority of strains are not susceptible to even the administration of multiple drugs [8]. Phage therapy for Burkholderia species has not yet reached clinical trials, preliminary studies have shown it to be safe and effective in the protection of crop seedlings and in both invertebrate and mammalian infection models [9,10,11,12]

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