596. Anti-Biofilm Activity of Isolated Bacteriophages Targeting Pseudomonas aeruginosa and Staphylococcus aureus

Abstract

Abstract Background A rise in the prevalence of antibiotic-resistant infections has prompted a search for alternative methods to combat bacteria in the human body. People with cystic fibrosis are especially vulnerable because their lung environment provides a habitable environment for chronic infection, biofilm formation, and antibiotic-resistant mutations. The difficulty associated with finding bacteriophages targeted to a specific infection is one reason the treatment is used relatively infrequently, even when antibiotics have failed. This study aimed to isolate phage species for strains of Pseudomonas aeruginosa and Staphylococcus aureus, the most common causes of chronic infections in patients with cystic fibrosis. Methods Phages targeting multidrug-resistant strains of S. aureus and P. aeruginosa were isolated from samples of fecal matter and soil; stocks were enumerated with the double agar overlay method. The potency of the Pseudomonas-hosted isolates in eradicating biofilms was compared to the efficacy of an antibiotic cocktail and the enzyme cellulase through an in vitro resazurin cell viability assay. Each treatment was performed in sextuplicate. Metabolic reduction of resazurin to resorufin was quantified at 24 and 48 hours of growth using a microplate reader. Results Six phage stocks (four targeting Pseudomonas bacteria [from human & feline fecal matter and from soil], two targeting Staphylococcus [from human & feline fecal matter]) contained bacteriophages at concentrations ranging from 3.9x104 pfu/mL to 2.8x107 pfu/mL. The most effective treatments in the assay were found to be cellulase alone and the three inhibitors together. Conclusion Feline fecal matter is a potential source of Pseudomonas and Staphylococcus bacteriophages. Enzymes were found to be a critical component of biofilm treatment. The isolated bacteriophages were not the most potent treatment alone, but when combined with cellulase and antibiotics, bacterial growth was markedly slowed. Disclosures All Authors: No reported disclosures.