Efficacy of Lytic Phage Cocktails on <i>Staphylococcus aureus</i> and <i>Pseudomonas aeruginosa</i> in Mixed-Species Planktonic Cultures and Biofilms
2020
Legesse Garedew Kifelew | Morgyn S. Warner | Sandra Morales | Nicky Thomas | David L. Gordon | James G. Mitchell | Peter G. Speck
The efficacy of phages in multispecies infections has been poorly examined. The <i>in vitro</i> lytic efficacies of phage cocktails AB-SA01, AB-PA01, which target <i>Staphylococcus aureus</i> and <i>Pseudomonas aeruginosa,</i> respectively, and their combination against their hosts were evaluated in <i>S. aureus</i> and <i>P. aeruginosa</i> mixed-species planktonic and biofilm cultures. Green fluorescent protein (GFP)-labelled <i>P. aeruginosa</i> PAO1 and mCherry-labelled <i>S. aureus</i> KUB7 laboratory strains and clinical isolates were used as target bacteria. During real-time monitoring using fluorescence spectrophotometry, the density of mCherry <i>S. aureus</i> KUB7 and GFP <i>P. aeruginosa</i> PAO1 significantly decreased when treated by their respective phage cocktail, a mixture of phage cocktails, and gentamicin. The decrease in bacterial density measured by relative fluorescence strongly associated with the decline in bacterial cell counts. This microplate-based mixed-species culture treatment monitoring through spectrophotometry combine reproducibility, rapidity, and ease of management. It is amenable to high-throughput screening for phage cocktail efficacy evaluation. Each phage cocktail, the combination of the two phage cocktails, and tetracycline produced significant biofilm biomass reduction in mixed-species biofilms. This study result shows that these phage cocktails lyse their hosts in the presence of non-susceptible bacteria. These data support the use of phage cocktails therapy in infections with multiple bacterial species.
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