Bacteriophages from ExPEC Reservoirs Kill Pandemic Multidrug-Resistant Strains of Clonal Group ST131 in Animal Models of Bacteremia

Abstract

Multi-drug resistant (MDR) enteric bacteria are of increasing global concern. A clonal group, Escherichia coli sequence type (ST) 131, harbors both MDR and a deadly complement of virulence factors. Patients with an immunocompromised system are at high risk of infections with these E. coli and there is strong epidemiologic evidence that the human intestinal tract, as well as household pets, may be a reservoir. Here, we examine if phages are an effective treatment strategy against this clonal group in murine models of bacteremia that recapitulate clinical infections. Bacteriophages isolated from known E. coli reservoirs lyse a diverse array of MDR ST131 clinical isolates. Phage HP3 reduced E. coli levels and improved health scores for mice infected with two distinct ST131 strains. Efficacy was correlated to in vitro lysis ability by the infecting phage and the level of virulence of the E. coli strain. Importantly, it is also demonstrated that E. coli bacteremia initiated from translocation across the intestinal tract in an immunocompromised host is substantially reduced after phage treatment. This study demonstrates that phage, isolated from the environment and with little experimental manipulation, can be effective in combating even the most serious of infections by E. coli “superbugs”.

Evaluation of the Activity of a Combination of Three Bacteriophages Alone or in Association with Antibiotics on Staphylococcus aureus Embedded in Biofilm or Internalized in Osteoblasts

“…First, the efficiency of plating (EOP) score was calculated. The latter is the ratio between the bacteriophage titer obtained with the HG001 strain divided by the titer obtained with the SH50-2 reference strain used for the production of bacteriophages; the closer this score is to 1, the more efficient the bacteriophages are (strong killers, EOP Ͼ 0.1; intermediate killers, 0.005 Ͻ EOP Ͻ 0.09; weak killers, EOP Ͻ 0.005) (32). Second, the growth inhibition of S. aureus by bacteriophages in liquid medium was assessed by culturing bacteria in a 96-well plate at a starting concentration of 10 7 CFU/ml with or without bacteriophages at two concentrations (multiplicity of infection [MOI] of 1 or 10 bacteriophages per bacteria).…”

Targeting of Mammalian Glycans Enhances Phage Predation in the Gastrointestinal Tract

“…These strains readily colonize the human intestine, which can become a reservoir, prior to extraintestinal infection (Nicolas-Chanoine, Bertrand and Madec, 2014). Previous studies reported that phage HP3, a lytic myovirus isolated from environmental reservoirs of ExPEC, could reduce ST131 bacteremia and disease severity in murine models of infection (Green et al, 2017a;Ma et al, 2018). Since the human gastrointestinal tract is the primary reservoir of ExPEC ST131, we wondered if phage HP3 could act prophylactically to reduce or eliminate ExPEC burden in the intestine.…”

“…Phages HP3, ES12, ES17, ES19, ES21 and ES26 have been previously described and characterized (Green et al, 2017a;Gibson et al, 2019). Phage 6914,6915 and 6939 were recently isolated from sewage.…”

Phage-Antibiotic Synergy is Driven by a Unique Combination of Antibacterial Mechanism of Action and Stoichiometry

“…To understand the range of possible outcomes on a bacterial growth when exposed to both phage and antibiotic, we assessed bacterial growth when exposed to concentrations of antibiotics that blankets the MIC across multiple orders of magnitude of phage titer over time in an optically-based microtiter plate assay system. The primary phage used throughout the investigation, Ф HP3, is a highly effective killer of the ST131 ExPEC clinical isolates and is commonly used as a prototype in the laboratory (24). Since an inoculum effect was observed with this isolate in the presence of different antibiotics ( Fig.…”

“…The clinical isolate ExPEC ST131 strain JJ2528 used in this study was kindly provided by Dr. James R. Johnson (56) and the plasmids (pTP123-CTX-M-14 WT and pTP123-CTX-M-14 A77V/D240G) that confer antibiotic resistance were kindly provided by Dr. Timothy Palzkill (25). The phages used in this study, Ф HP3 and Ф ES12, were previously isolated from environmental sources (24,55). All antibiotics were prepared fresh, and filter sterilized (except chloramphenicol and trimethoprim due to solvent used for these antibiotics).…”