Specific targeting of O25b-ST131 Escherichia coli strains with a fast T7-like bacteriophage
Amongst the highly diverse E. coli population, the O25b-ST131 clonal complex is of particular concern: as pathogenic strains they belong to the B2 phylogroup (where most extraintestinal-pathogenic E. coli classify), they express a large number of virulence factors and are involved in community as well as hospital-acquired infections. Since their first descriptions in few countries in 2008, O25b-ST131 isolates are now present worldwide and associated with a high level of resistance to betalactams (mainly by producing CTX-M-15 extended spectrum betalactamase) and fluoroquinolones.
Using an O25b-ST131 strain responsible for a ventilator-associated pneumonia in an intensive care unit patient, we isolated a lytic Podoviridae, named LM33_P1. From a collection of E. coli strains displaying various O-type (n=283), we found that LM33_P1 infect exclusively O25b strains (100% specificity). Within the one hundred O25b strains tested, 64% were lysed by this bacteriophage with a median efficiency of plaquing of 0.46 [0.09-1.27]. Interestingly, this coverage rate increases to 70% among STs particularly concerned by antibiotic resistance (ST131 and ST69). Using immunology, biochemistry and genetic-based methods, we showed that the specific interaction of LM33_P1 with O25b strains is LPS-dependent. Genome sequence of LM33_P1 revealed its proximity to coliphage K1F. In vitro characterization of LM33_P1 demonstrated it is the fastest T7-like bacteriophage reported to date with short eclipse and latent periods (respectively 7 and 9 minutes), high adsorption constant (1.2x10-8 mL/min) and a burst size of 300 PFU. In vivo activity of LM33_P1 was also investigated in three animal models (pneumonia, septicemia and urinary tract infection) showing its efficacy in reducing bacterial load in several organs.
Such bacteriophage is of particular interest for therapeutic approaches but also for prophylaxis: the targeting of O25b-ST131 intestinal carriage could be used to stop or at least slow down the spread of these strains between humans, especially in healthcare environments.
Using an O25b-ST131 strain responsible for a ventilator-associated pneumonia in an intensive care unit patient, we isolated a lytic Podoviridae, named LM33_P1. From a collection of E. coli strains displaying various O-type (n=283), we found that LM33_P1 infect exclusively O25b strains (100% specificity). Within the one hundred O25b strains tested, 64% were lysed by this bacteriophage with a median efficiency of plaquing of 0.46 [0.09-1.27]. Interestingly, this coverage rate increases to 70% among STs particularly concerned by antibiotic resistance (ST131 and ST69). Using immunology, biochemistry and genetic-based methods, we showed that the specific interaction of LM33_P1 with O25b strains is LPS-dependent. Genome sequence of LM33_P1 revealed its proximity to coliphage K1F. In vitro characterization of LM33_P1 demonstrated it is the fastest T7-like bacteriophage reported to date with short eclipse and latent periods (respectively 7 and 9 minutes), high adsorption constant (1.2x10-8 mL/min) and a burst size of 300 PFU. In vivo activity of LM33_P1 was also investigated in three animal models (pneumonia, septicemia and urinary tract infection) showing its efficacy in reducing bacterial load in several organs.
Such bacteriophage is of particular interest for therapeutic approaches but also for prophylaxis: the targeting of O25b-ST131 intestinal carriage could be used to stop or at least slow down the spread of these strains between humans, especially in healthcare environments.
Reference:
Poster Day 4-T12-Pos-03
Session:
Posters Covering the use of viruses to control infection and Processes governing the applied use of viruses
Presenters:
Nicolas DUFOUR
Session:
Day 4 Posters Covering: The use of viruses to control infection and Processes governing the applied use of viruses
Presentation type:
Poster presentation
Room:
Poster Halls
Date:
Thursday, 21 July 2016
Time:
12:05 - 15:30