The antibacterial effect of ceftazidime and vitamin C against Pseudomonas aeruginosa in Drosophila model of infection

Background: The rise of antimicrobial resistance among bacteria necessitates the exploration of alternative therapeutic strategies. One potential approach is combining antibiotics with vitamins to improve antimicrobial efficacy. This study investigates the synergistic effect of ceftazidime and vitamin C against Pseudomonas aeruginosa using Drosophila melanogaster larvae as an in vivo model. Results: A series of microbiological, phenotypic, and molecular assays were conducted to evaluate the antibacterial effects of ceftazidime combined with vitamin C in the Drosophila model. Ceftazidime’s minimum inhibitory concentration (MIC) decreased from 12.5 to 6.25 µM when combined with vitamin C, according to the microdilution checkerboard assay. According to in vivo tests, D. melanogaster larvae treated with the antibiotic–vitamin C combination had a significantly higher survival rate (p < 0.05) than the infection control group. Colony-forming unit analysis on cetrimide agar medium showed no bacterial growth in the group treated with ceftazidime and vitamin C. Additionally, gene expression analysis demonstrated that ceftazidime treatment alone decreased Dpt gene expression through the IMD pathway, whereas the combination treatment elevated Dpt expression, reflecting the immunostimulant properties of vitamin C. Conclusion: This study shows enhanced efficacy of ceftazidime when combined with vitamin C in the D. melanogaster larvae model. These findings parallel results from mammalian systems and support the use of Drosophila as a valuable pre-screening model for drug repurposing efforts aimed at combating antimicrobial resistance.