Rob Lavigne

In recent years, bacteriophages (or phages) have reentered the spotlight as alternative or adjuvant therapeutic agents to antibiotics. Their efficacy in more recalcitrant forms of infections like biofilms, frequently encountered in the orthopedic setting, remains less characterized. The present study aimed at evaluating the activity of phage-antibiotic combinations against Pseudomonas aeruginosa biofilms. A large collection of phages was de novo isolated from a wide variety of environmental sources. Three phages with a large host range against a.o. clinical orthopedic isolates, PSP2 ( Yuavirus ), PSP3 ( Pbunavirus ), and PSP30 ( Bruynoghevirus ), were selected for phage-antibiotic synergy assays on mature P. aeruginosa PAO1 biofilms. Phages were combined with ciprofloxacin, meropenem, and ceftazidime, all used as standard of care in bone-related infections. Significant reductions in both cell counts and biomass were observed for all phage-antibiotic combinations. The highest reduction in viable cell counts was observed for PSP3 and PSP2 in combination with ceftazidime [4.58 and 4.30 log 10 Colony Forming Units (CFU)/well], followed by all phage combinations with ciprofloxacin (up to 3.56 log 10 CFU/well). The highest reduction in biomass was obtained by combining PSP3 with ciprofloxacin (29.8%). Metabolic assays confirmed these findings with reductions in biofilm respiratory rate of up to 65%. Scanning electron microscopy imaging of PAO1 biofilms grown on titanium coupons and treated by ciprofloxacin and PSP30 confirmed the efficacy of the combined treatment with PSP30 and ciprofloxacin. This study highlights the synergetic effects of phage-antibiotic combinations on P. aeruginosa biofilms, thereby offering a promising approach to combat biofilm-associated infections. IMPORTANCE Biofilm-related infections are among the most difficult-to-treat infections in all fields of medicine due to their antibiotic tolerance and persistent character. In the field of orthopedics, these biofilms often lead to therapeutic failure of medical implantable devices and urgently need novel treatment strategies. This forthcoming article aims to explore the dynamic interplay between newly isolated bacteriophages and routinely used antibiotics and clearly indicates synergetic patterns when used as a dual treatment modality. Biofilms were drastically more reduced when both active agents were combined, thereby providing additional evidence that phage-antibiotic combinations lead to synergism and could potentially improve clinical outcome for affected patients.

The second symposium of the Belgian Society for Viruses of Microbes (BSVoM) took place on 8 September 2023 at the University of Liège with 141 participants from 10 countries. The meeting program covered three thematic sessions opened by international keynote speakers: two sessions were devoted to “Fundamental research in phage ecology and biology” and the third one to the “Present and future applications of phages”. During this one day symposium, four invited keynote lectures, nine selected talks and eight student pitches were given along with thirty presented posters. The president of the Belgian Society for Viruses of Microbes, Prof. Yves Briers, took advantage of this symposium to launch the Phage Valley concept that will put the spotlight on the exceptionally high density of researchers investigating viruses of microbes as well as the successful triple helix approach between academia, industry and government in Belgium.