An IgM monoclonal antibody targeting diguanylate cyclase DgcE potentiates gentamicin activity against avian pathogenic Escherichia coli through modulation of c-di-GMP signaling.

BACKGROUND

The combination of monoclonal antibodies with aminoglycosides represents a promising strategy to counter the increasing prevalence of aminoglycoside resistance in avian pathogenic E. coli (APEC). Although the diguanylate cyclase DgcE (UniProt: P38097) is known to regulate virulence through c-di-GMP signaling, its potential as a therapeutic target has not been investigated.

RESULTS

In this study, five female BALB/c mice were immunized to generate a monoclonal antibody. We developed an IgM monoclonal antibody (E11G12) targeting a defined region of DgcE and evaluated its ability to potentiate gentamicin activity. Structural prediction and docking analyses suggested specific binding interactions within the targeted DgcE region. In vitro checkerboard assays demonstrated synergistic activity between E11G12 and gentamicin (FICI ≤ 0.5), and time-kill assays showed enhanced bactericidal activity compared to monotherapy. Treatment was associated with reduced intracellular c-di-GMP levels and increased gentamicin accumulation.

CONCLUSION

These findings suggest that the E11G12-aminoglycoside combination exhibits synergistic anti-APEC activity, potentially through blocking virulence via DgcE inhibition and enhancing antibiotic efficacy in association with c-di-GMP suppression. This approach offers a novel therapeutic strategy against drug-resistant APEC infections.