20th Evergreen Phage Meeting Presentation: Animal models of surgical phage applications
This presentation highlights animal models used to determine the efficacy of surgical phage applications, as well as highlight our findings on using phage therapy to prevent the development of osteomyelitis in a rat model.
The rise in bacterial resistance to antibiotics has propelled many researchers to reevaluate the efficacy of phage therapy following systematic and controlled experimental designs. Although many have investigated the effectiveness of phage therapy as a topical application to treat localized infections, requiring less purified phage preparations, some researchers have undertaken the challenging task of using systemically administered phages to determine if phage therapy can be used against prevalent bacterial infections caused by Staphylococcus aureus, Enterococcus faecium and Klebsiella pneumoniae, which reside in hospitals today. In addition, infections associated with implants such as catheters, heart valves and orthopaedic devices are a growing problem, and our increasing use of implants makes this problem a high priority issue to solve as an infection prevention and control strategy.
Bacterial infections of bone (osteomyelitis) and of bone implant-devices are difficult diseases to treat. For the last 2 years our group has focused on testing the efficacy of Staph phage K to prevent the development of osteomyelitis in a rat model. Using a bioluminescent strain of S. aureus and an in-vivo imaging system (IVIS Lumina II) we were able to monitor the progression of infection in live animals and assess the efficacy of the phage treatment on the bone infection in ‘real-time’, without sacrificing animals until the end point of the study. To determine the dosing strategy we tested the persistence of the systemically administered pharmaceutical-grade phage via intraperitoneal, intravenous and subcutaneous injections to healthy rats.
Following a single dose of Staph phage K (~4x109 PFU), the circulating phage was estimated to be 1x108 PFU/mL. Phage densities peaked at 2 hours post injection and were undetectable by 24 hours. The spleen was found to harbor the largest concentration of infective phage at 30 hours post injection. No gross clinical manifestations or adverse effects were seen. From these results, the route of administration for delivering a reproducible density of phage to the circulatory system was via the IV route. Using a bacterial inoculum of ~2x107 CFU and an IV administered single dose of phage (~8x109 PFU), no notable differences were seen in the development of osteomyelitis by day-14 post surgery between the treated and untreated rats. However, viable phage were detected in the rat blood plasma up to 45 hours after the initial phage treatment. Multiple daily phage treatments over a 4-day period also failed to prevent the development of osteomyelitis by day-14, despite the presence of phage being detected in the rat blood plasma up to 78 hours post initial treatment.