Development and validation of a miniaturized host range screening assay for bacteriophages

Antimicrobial resistance is a global health crisis, partly contributed by inappropriate use of antibiotics. The increasing emergence of multidrug resistant infections has led to the resurgent interest in bacteriophages as an alternative treatment. Current procedures assessing susceptibility and breadth of host range to bacteriophage are conducted using large-scale manual processes that are labor-intensive. The aim here was to establish and validate a scaled down methodology for high-throughput screening in order to reduce procedural footprint. Bacteriophages were isolated from wastewater samples and screened for specificity against 29 clinical Pseudomonas aeruginosa isolates and PA01 using a spot test (2 L/ drop). Host range assessment was performed on four representative P. aeruginosa isolates using both double agar overlay assay on petri dishes and 24-well culture plates. The breadth of host range of bacteriophages that exhibited lytic activity on P. aeruginosa isolates were corroborated between the current standard practice of whole plate phage assay and 24-well phage assay. The high correlation achieved in this study confirms miniaturization as the first step in future automation that could test phage diversity and efficacy as antimicrobials.