Background
Bacteriophages are ubiquitous viruses that infect specific bacteria, forcing them to produce viral progeny and often resulting in bacterial lysis and death. Bacteriophages are being increasingly used as alternatives to antibiotics as the frequency of antimicrobial resistance increases.
Aim
This study was designed to evaluate the efficacy of six (DSP01, DSP02, DSP03, DSP04, DSP05 and DSP06) newly isolated phages to kill Pseudomonas aeruginosa isolates that had been isolated from sight threatening ocular infections.
Methods
Twenty-seven ocular P. aeruginosa and three standard isolates (PAO1, ATCC PA6294 and ATCC PA9027), including antibiotic resistant and multi-drug resistant (MDR) isolates, were investigated for their sensitivity to six bacteriophages that had been isolated from environmental water samples using a spot plate assay. Briefly, 1ml of stationary phase bacterial culture was mixed with 3ml of molten agar (50-55oC) and this was poured onto prepared tryptic soy agar plates (TSA). The agar was allowed to gel for about 15 minutes after which 5mL of each phage was spotted onto the surface. The plates were left to air dry and then incubated at 370C for 18-24 hours. After incubation, any lysis of the bacterial cells was recorded.
Results
Out of the six tested phages, phage DSP04 was most active, killing 70% of the ocular P. aeruginosa isolates. This was followed by DSP03 (66%), DSP01 and DSP05 (43%), DSP02 (40%) and DSP06 (33%). The MDR ocular isolates were sensitive to at least two bacteriophages. Only two ocular isolates (212 and 218) both isolated from India were not sensitive to any of the bacteriophages.
Conclusion
Bacteriophages can be active against the ocular P. aeruginosa isolates and might provide a better treatment option for infection caused by MDR isolates. Future experiments will study whether cocktails of the most active phages can be used to increase the spectrum of activity against P. aeruginosa.