Microbiological rationale for alternative strategies to combat infections caused by antibiotic-resistant Pseudomonas aeruginosa

Abstract

This study aimed to investigate the activity of the drug Pyofag against clinical isolates of Pseudomonas aeruginosa and to evaluate the effectiveness of the combined action of surface-active antiseptics and bacteriophages. To achieve this aim, classical methods for the isolation and identification of bacteria were employed. Antibiotic susceptibility of Pseudomonas isolates was determined using the disc diffusion method, while susceptibility to surface-active antiseptics (decamethoxine, benzalkonium chloride, chlorhexidine bigluconate, octenidine dihydrochloride, and polyhexanide) was assessed using the broth dilution method. The susceptibility of clinical isolates to Pyofag was evaluated based on the optical density of bacterial suspensions after 18 hours of incubation with the preparation. The nature of the combined effect of bacteriophages and antiseptics on P. aeruginosa was assessed by calculating the lytic index of the phage on planktonic bacterial forms cultured in media containing sub-bacteriostatic concentrations of antiseptics. The results showed that all 54 isolated clinical strains of P. aeruginosa retained high susceptibility only to reserve antibiotics – colistin (94.4%) and cefiderocol (75.9%). Resistance to other antipseudomonal antibiotics (cefepime, ceftazidime, piperacillintazobactam, imipenem, and ciprofloxacin) was observed in 96.3%-100% of isolates. However, aminoglycosides (gentamicin, tobramycin, amikacin) and meropenem remained effective against 29.6%-44.4% of strains. Antiseptic agents containing surface-active compounds demonstrated strong antipseudomonal properties and are capable of inhibiting bacterial proliferation at concentrations ranging from 16.4-22.5 μg/mL (octenidine dihydrochloride, decamethoxine, chlorhexidine bigluconate) to 65-145.7 μg/mL (polyhexanide, benzalkonium chloride). It was confirmed that decamethoxine, octenidine, and chlorhexidine exhibit significantly greater antibacterial activity than polyhexanide and benzalkonium chloride (p<0.01). The isolated Pseudomonas strains showed high susceptibility to the pharmaceutical preparation Pyofag: the lytic activity index (Is) of Pyofag exceeded 0.5 in 70.4% of strains, indicating that 50% of the bacterial population was destroyed during the dynamic interaction between bacterial growth and phage replication. In media containing sub-bacteriostatic concentrations of decamethoxine, chlorhexidine, or octenidine, both susceptible (n = 7, Is = 0.69) and resistant (n = 8, Is = 0.15) strains were lysed more intensively by the bacteriophage. This was evidenced by an increase in the susceptibility index to 0.80-0.87 in susceptible strains and to 0.54-0.70 in phage-resistant strains, respectively

Received: 06.01.2025 | Revised: 17.04.2025| Accepted: 27.05.2025