| Sumario: | Background & Objective: This study examines the in vitro antimicrobial properties of black and yellow grape juice and raisin extracts against 12 Grampositive and Gram-negative bacterial strains, as well as five Candida species. Materials & Methods: Cell viability was assessed by MTT assay, antibacterial activity by disk diffusion, MIC and MBC tests, biofilm inhibition by a microtiter plate method, and wound healing potential by a scratch assay. Results: MTT assay showed that black and yellow grape juices and yellow raisins were non-toxic up to 30 µg/mL, while black raisins were safe only up to 15 µg/mL. Disk diffusion demonstrated antibacterial activity of all extracts against most tested bacterial except A. baumannii and Methicillin-resistant S. aureus. The strongest inhibition zones were observed for P. aeruginosa, Enterococcus, S. epidermidis, L. monocytogenes, and S. maltophilia, varying by extract type, while E. coli and E. coli O157 showed the lowest sensitivity. None of the extracts showed antifungal activity against Candida species. The lowest MIC observed for the yellow and black raisin extracts was 15 µg/mL against Enterococcus and S. maltophilia. In the yellow and black grape juice, the lowest MIC against S. epidermidis, Enterococcus, and S. maltophilia was 30 µg/mL. Black grape juice showed the greatest inhibition of P. aeruginosa biofilm formation. Both yellow and black grape juices promoted wound healing. Conclusion: Grape extracts may serve as promising natural sources for the development of novel antibacterial agents against the tested Gram-positive and Gram-negative bacteria.
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