Comparative study of antibacterial activities of bacteriophage PA5 and polymyxin on the model of lethal pseudomonas infection in mice
The spread of multiple drug resistant bacteria is a serious problem in practical healthcare. The era of effective use of classical antibiotics to combat bacterial infections is a thing of the past. Currently, intensive search for combined antibiotic therapy as well as novel alternative antimicrobials is underway. Of particular scientific interest are bacteriophages, bacterial viruses, capable of lysing both antibiotic-susceptible and -resistant bacterial strains. We studied a therapeutic - and- prophylactic effect of the lytic phage PA5 using two models of Pseudomonas aeruginosa lethal infection, primary sepsis and femoral soft tissue infection, in BALB/c mice. The preventive i/p injection of the phage at 10<sup>8</sup> PFU to mice with P. aeruginosa sepsis resulted in the 100% survival of the mice. The 5-day therapeutic injection of the phage provided a therapeutic effect 1.5h after infection in 70-80% of cases. The phage PA5 used for preventing or treating Pseudomonas aeruginosa femoral soft tissue infection did not produce a positive therapeutic effect, leading to death of all animals i/m infected with P. aeruginosa PAO1 or P. aeruginosa B1304 culture at day 1 or 6. Meantime polymyxin B (10 mg/kg, twice a day for 5 days) saved mice with sepsis or femoral soft tissue infection in 100% of cases. Results conclude that the phage PA5 antibacterial activity in vivo is similar to that of polymyxin, but just in preventing and treating Pseudomonas aeruginosa sepsis in mice. The phage is ineffective in treating Pseudomonas aeruginosa lethal femoral infection, while the antibiotic cures mice infected with P. aeruginosa PAO1 or P. aeruginosa B1304 cultures in 100% of cases.