Pseudomonas aeruginosa Virulence Bacteriophage Isolated From Inflammatory Mouse Feces Exhibits Bactericidal Activity in Infected Wounds of a Mouse Model.

BACKGROUND

Recently, bacteriophages have risen as a potent therapy for superbug infections. The mammal gut demonstrates an interesting source of virulence bacteriophages. The gut with inflammation is phage-rich; therefore, we primarily aimed to prove the concept that an inflammatory gut is a possible source of effective phages and to evaluate the efficacy of the candidate phage against Pseudomonas aeruginosa in vitro and in a mouse model of infected wounds.

RESULTS

The gut microbiome of cecal ligation and puncture (CLP) sepsis mice, an animal model of inflammation, showed a dominant presence of Podoviruses. CLP bacteriophages (CLP Φ1-Φ4), of which the CLP Φ4 possessed the broadest bactericidal activity (viable bacterial cell reduction in time-kill study) against P. aeruginosa isolates. The CLP Φ4 specifically killed the Pseudomonas aeruginosa clinical (PACL) strain with two huge burst events. Although the CLP Φ4 had no effect on ex vivo mouse bone marrow-derived macrophage (BMDM) cytokine gene expression and cytokine production, the CLP Φ4 attenuated the severity of the P. aeruginosa-infected wound mouse model after treatment. P. aeruginosa PACL exhibited significantly pathogenic characteristics in a mouse model, including excessive bacterial loads (in wounds and internal organs, indicating the systemic infection due to localized infected wound with P. aeruginosa), increased IL-6 cytokine (in serum), upregulated IL-6 expression (in wounds), and immune cell infiltration (in wounds), indicating severe inflammation. In the CLP Φ4 treatment alone, the wound tissues upregulated IL-10 expression and recruited inflammatory cells. Interestingly, the three-day CLP Φ4 treatment was adequate to eradicate P. aeruginosa PACL in the wounds and other internal organs. After treatment, the mouse serum cytokine showed a remarkably decreased IL-6. Likewise, IL-6 downregulation and IL-10 upregulation were demonstrated in the treated wounds, suggesting an anti-inflammatory shift. These results demonstrated the effectiveness (bacterial wound and internal organ clearance and cytokine modulation) of the CLP Φ4 in the P. aeruginosa-infected wound and systemic infection. Finally, the CLP Φ4 isolation verified a proof of concept that the irritated gut acts as a source of bacteriophages.

CONCLUSIONS

The gut virome was a promising and interesting source of antimicrobial and immunomodulating bacteriophage.