Sodium butyrate augments the antibacterial activity of tetracycline against clinical isolates of multidrug-resistant Vibrio cholerae

Background Antibiotic resistance poses a major challenge in treating Vibrio cholerae infections. One promising method to counter resistance is the co-administration of antibiotics with non-antibiotic adjuvants to enhance their efficacy. This study investigated the combined action of sodium butyrate (SB) and tetracycline on tetracycline-resistant V. cholerae strains.
Results The combined activity of SB and antibiotics was assessed on eight V. cholerae clinical isolates using the Fractional Inhibitory Concentration Index (FICI), with SB-Tetracycline showing strong synergy (FICI: 0.09–0.5). Functional and mechanistic studies, including time-kill kinetics, live/dead staining, SEM-based morphological analysis, and fluorometric assays, demonstrated a synergistic antibacterial effect of SB and Tetracycline. This effect was associated with increased membrane permeability, disruption of membrane integrity, dissipation of the proton motive force, and suppression of efflux activity. These changes collectively led to membrane damage, enhanced intracellular accumulation of Tetracycline, decreased intracellular ATP levels, and ultimately, bacterial cell death. Moreover, GM1-CT ELISA and fluorescence microscopy revealed the synergistic anti-virulence activity of the SB- Tetracycline combination. Finally, the combination of SB and Tetracycline showed enhanced efficacy in animal models compared with monotherapy.
Conclusion: The observed SB-Tetracycline synergy provides a promising therapeutic approach to overcome tetracycline resistance in V. cholerae, offering a potential adjunct strategy for the management of antibiotic-resistant cholera infections.