Abstract Aims The aim of this study was to assess the antimicrobial and antibiofilm activity of wastewater bacteriophages in combination with conventional drugs against relevant Gram-negative pathogens in vitro. Methods and Results Host bacterial strains (Stenotrophomonas spp, Burkholderia spp, and Achromobacter spp.) were obtained from a third-level hospital in Mexico. The antimicrobial susceptibility profile and biofilm production of these strains were assessed by broth microdilution and crystal violet staining. Environmental bacteriophages isolated from wastewater were tested against the host strains using the spot test. Phage purification and titration were performed using the double-layer LB agar method. The antibiofilm activity in combination with conventional antibiotics were assessed. Lytic activity of the environmental bacteriophages was observed against Stenotrophomonas maltophilia (Sma2), Achromobacter denitrificans (Ade2), and Achromobacter xylosoxidans (Axy4). The latent period of the bacteriophages was 20˗30 min, and the estimated burst size was H 12 to 300 phages per infected cell. The bacteriophage Ade2 showed strong binding affinity, efficient attachment and continuous lytic activity. The activity of isolated phages against the bacterial strains in their biofilm state showed enhanced antibiofilm activity with meropenem against A. denitrificans and A. xylosoxidans; and trimethoprim-sulfamethoxazole against A. xylosoxidans and S. maltophilia. Conclusions Wastewater environmental bacteriophages showed enhanced activity in vitro against biofilm-associated infections caused by Achromobacter and Stenotrophomonas species in combination with conventional drugs, such as meropenem and trimethoprim-sulfamethoxazole, which otherwise would show resistance.
Flores-Ibarra et al. (Sat,) studied this question.