Sewage and sewage-contaminated environments are the most prominent sources to isolate phages against Pseudomonas aeruginosa.

BACKGROUND: P. aeruginosa is the primary source of hospital-acquired infections. Unfortunately, antibiotic resistance is growing to precariously high levels, making the infections by this pathogen life-threatening and hard to cure. One possible alternative to antibiotics is to use phages. However, the isolation of phages suitable for phage therapy- be lytic, be efficient, and have a broad host range -against some target bacteria has proven difficult. To identify the best places to look for these phages against P. aeruginosa we screened hospital sewages, soils, and rivers in two cities. RESULTS: We isolated eighteen different phages, determined their host range, infection property, and plaque morphology. We found that the sewage and sewage-contaminated environments are the most reliable sources for the isolation of Pseudomonas phages. In addition, phages isolated from hospital sewage showed the highest efficiency in lysing the bacteria used for host range determination. In contrast, phages from the river had larger plaque size and lysed bacteria with higher levels of antibiotic resistance. CONCLUSIONS: Our findings provided additional support for the importance of sewage as the source of phage isolation.

Improving the Inhibitory Effect of Phages against Pseudomonas aeruginosa Isolated from a Burn Patient Using a Combination of Phages and Antibiotics.

Antibiotic resistance causes around 700,000 deaths a year worldwide. Without immediate action, we are fast approaching a post-antibiotic era in which common infections can result in death. Pseudomonas aeruginosa is the leading cause of nosocomial infection and is also one of the three bacterial pathogens in the WHO list of priority bacteria for developing new antibiotics against. A viable alternative to antibiotics is to use phages, which are bacterial viruses. Yet, the isolation of phages that efficiently kill their target bacteria has proven difficult. Using a combination of phages and antibiotics might increase treatment efficacy and prevent the development of resistance against phages and/or antibiotics, as evidenced by previous studies. Here, in vitro populations of a Pseudomonas aeruginosa strain isolated from a burn patient were treated with a single phage, a mixture of two phages (used simultaneously and sequentially), and the combination of phages and antibiotics (at sub-minimum inhibitory concentration (MIC) and MIC levels). In addition, we tested the stability of these phages at different temperatures, pH values, and in two burn ointments. Our results show that the two-phages-one-antibiotic combination had the highest killing efficiency against the P. aeruginosa strain. The phages tested showed low stability at high temperatures, acidic pH values, and in the two ointments. This work provides additional support for the potential of using combinations of phage-antibiotic cocktails at sub-MIC levels for the treatment of multidrug-resistant P. aeruginosa infections.