Comparative evaluation of commercial bacteriophages and prospects for their application in the treatment of orthopedic MRSA-infection

Introduction Phage therapy is a promising approach to addressing the problem of antibiotic resistance in orthopedic infection pathogens. Staphylococci are the leading etiotropic agents of implant-associated infections, with 15 % of S. aureus strains being methicillin-resistant (MRSA). Bacteriophage preparations are available on the Russian pharmaceutical market, and the concentration of phages active against the microbial agent influences their effectiveness.

The objective was to compare the activity of commercial bacteriophage kits against methicillin-resistant Staphylococcus aureus isolated from patients with orthopedic infections.

Material and methods Clinical strains of S. aureus (n = 25), consecutively isolated from patient biomaterial in 2025 were examined. Identification was performed using MALDI-TOF MS, and antibiotic susceptibility assessed according to EUCAST v.15. Phage lytic activity was evaluated using meat-peptone agar and a five-point scale with the strain sensitivity to a specific drug determined as sensitive, weakly sensitive, or resistant. Statistical analysis was performed using IBM SPSS Statistics v.26.

Results The S. aureus strains included in the study were resistant to cefoxitin. Of the MRSA strains tested, the majority (76 %) were sensitive to PBP 1. A larger number of strains (60%) were classified as "weakly sensitive" to PBP 3. There were less variations in "non-susceptible" cultures, with only one strain demonstrating resistance to the three bacteriophage preparations. A comparative analysis of antistaphylococcal drugs from various manufacturers revealed differences in the activity against clinical MRSA isolates. There were 84 % isolates being sensitive to PBP 4 and 36 % to PBP 5. One isolate was resistant to the phages tested.

Discussion The differences in the activity of commercial phages could be associated with the composition of the resulting preparations, which had lower affinity for strains isolated from patients in other regions. Given the wide geographical distribution of patients with orthopedic infections hospitalized in federal centers, the ability to choose bacteriophages from a wide range of commercial kits available on the market increases the likelihood of their successful use.

Conclusion Commercial drugs presented on the Russian market were characterized by different lytic activity against clinical strains of MRSA, with Pyophag® and Staphylophag® exhibiting greater activity.

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