Differential modulation of gentamicin antibacterial activity by vitamin B12 and vitamin D3 against Gram-positive and Gram-negative bacteria: an <i>in vitro–in silico</i> study

INTRODUCTION: approach. MATERIALS AND METHODS: analyses targeted the 30S ribosomal subunit, a cobalamin riboswitch, and a proton motive force (PMF)-related protein to explore mechanistic interactions underlying observed phenotypes. RESULTS: . Conversely, vitamin D3 displayed antagonistic effects (MFR ≤ 0.5) in several Gram-positive strains, increasing gentamicin MICs by up to 16-fold. Computational results indicated cooperative stabilization of gentamicin at the ribosomal target and increased affinity for the cobalamin riboswitch in the presence of vitamin B12, whereas vitamin D3 showed strong binding to a PMF-related protein, consistent with impaired aminoglycoside uptake. CONCLUSION: Vitamin B12 represents a promising dose-sparing adjuvant for gentamicin, while vitamin D3 may compromise aminoglycoside efficacy under the tested conditions. These findings warrant further validation using clinical isolates and biofilm models before considering vitamin-based strategies in aminoglycoside stewardship.