Successful Intratracheal Treatment of Phage and Antibiotic Combination Therapy of a Multi-Drug Resistant Pseudomonas aeruginosa Murine Model

Abstract

Background: Pseudomonas aeruginosa (PsA) is a common etiology of bacteria-mediated lower respiratory tract infections, including pneumonia, hospital acquired pneumonia (HAP), and ventilator-associated pneumonia (VAP). Given the paucity of novel antibiotics in our foreseeable pipeline, developing novel non-antibiotic antimicrobial therapies saliently targeting drug resistant PsA isolates remains a priority. Lytic bacteriophages (or phages) have come under scrutiny as a potential antimicrobial for refractory bacterial infections. We evaluated intratracheally and intraperitoneally (IP) administered phage therapy (with/without meropenem) in an acute immunocompromised mouse model of multi-drug resistant (MDR) PsA pulmonary infection. The MDR P. aeruginosa respiratory disease model used in these studies was developed to investigate novel therapies that might have efficacy as either monotherapies or as combination therapy with meropenem. Methods: We utilized eight-week-old, 18 g BALB/cJ female mice and an MDR strain of PsA (UNC-D). Mice were immunosuppressed with cyclophosphamide. We employed a three-phage cocktail targeting PsA (PaAH2ΦP (103), PaBAP5Φ2 (130), and PaΦ (134)), confirmed to exhibit in vitro suppression of the infecting isolate out to 45 h. Suppression was confirmed with phages acting in isolation and in combination with meropenem. Results: IP administration of phage did not protect mice from death. A one-time delivery of phage directly to the lungs via a single intubation-mediated, intratracheal (IMIT) instillation protected mice from lethal infection. Protection was observed despite delaying therapy out to 6 h. Finally, we observed that, by slowing the progression of infection by treatment with a sub-efficacious dose of meropenem, we could protect the mice from lethal infection via IP phage administration coupled to meropenem, observing partial additive effects of phage–antibiotic combination therapy. Conclusions: A personalized phage cocktail administered via IMIT exhibits high therapeutic efficacy, despite delayed treatment of 6 h in a lethal MDR PsA pneumonia model. IP phage alone did not forestall mortality, but exhibited efficacy when combined with meropenem and IMIT-administered phage. These additive effects of combined IP phage and meropenem confirm that phage may indeed reach the lung bed via the systemic circulation and protect mice if the infection is not too acute. Therefore, adjunctive phage therapy with concerted attention to identifying optimal phage targeting of the infecting isolate in vitro may exhibit transformative potential for combating the specter of MDR bacterial infections. Phage should serve as an integral component of a four-pronged approach coupled with antibiotics, source control, and immune optimization.

Repetitive Exposure to Bacteriophage Cocktails against Pseudomonas aeruginosa or Escherichia coli Provokes Marginal Humoral Immunity in Naïve Mice

“…In the context of lung infections with MDR-bacteria, phage therapy is of great interest for treating VAP patients. While recent studies used intratracheal applications [ 74 ] or nebulized phage suspensions [ 7 , 75 , 76 ], here we show that systemic applications of two different phage cocktails are suitable for the dissemination of phages to the lung. The phage cocktails are well-tolerated and do not induce a marked immune response in naïve mice warranting their future evaluation as antibacterial therapeutics.…”

A Novel Zinc (II) Porphyrin Is Synergistic with PEV2 Bacteriophage against Pseudomonas aeruginosa Infections

“…While extant antibiotics and phages have unique antimicrobial effects individually, using them in combination is a promising option for persistent infections [ 50 , 51 , 52 ]. The goal of phage–antibiotic synergy (PAS) is to use a combination of a phage and an antibiotic to create a synergistic action against pathogenic bacteria, thereby evading or minimizing the development of bacterial resistance.…”

“…The goal of phage–antibiotic synergy (PAS) is to use a combination of a phage and an antibiotic to create a synergistic action against pathogenic bacteria, thereby evading or minimizing the development of bacterial resistance. For example, Duplessis showed that when merged with a sub-efficacious dose of meropenem, a combination of phages reduced the bacterial burden of an antibiotic-resistant strain of PsA and decreased mortality in a murine pneumonia model [ 52 ].…”

Validated Preclinical Mouse Model for Therapeutic Testing against Multidrug-Resistant Pseudomonas aeruginosa Strains

“…This model was chosen because it has been well characterized to mimic human disease, with bacterial proliferation in the lungs, acute inflammation, and development of pneumonia ( 10 – 12 ). Using this model, we have successfully evaluated the efficacy of numerous therapies either as monotherapy or as combination therapy with a representative carbapenem antibiotic, namely, meropenem ( 10 , 13 , 14 ). However, this model has limitations, including characterization with only one strain of P. aeruginosa and a lack of robust comparative antibiotics to gauge the success of novel INDs.…”