Background: The emergence of antibiotic-resistant strains, including methicillin-resistant and vancomycin-resistant Staphylococcus aureus (MRSA and VRSA) and vancomycin-resistant Enterococcus (VRE), represents a serious challenge in public health, the food industry, and clinical care. This study aimed to investigate the role of probiotic strains in the inhibition mechanisms of methicillin-resistant S. aureus and vancomycin-resistant Enterococcus.

Methods: The antibacterial activity of four probiotic strains, Lactobacillus plantarum, Lactobacillus casei, Lactobacillus acidophilus, and Bifidobacterium animalis, was evaluated against clinical and foodborne isolates of MRSA and VRE. Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), well diffusion, and disk diffusion assays were performed according to CLSI guidelines.

Results: All assays demonstrated consistent trends, showing that L. plantarum exhibited the strongest antibacterial activity against both target bacteria. This strain showed the lowest MIC and MBC values (0.125) and produced the largest inhibition zones in the well-diffusion (2.5 cm) and disk-diffusion (approximately 2 cm) assays. L. casei exhibited the next highest activity, while L. acidophilus and B. animalis showed moderate and minimal antibacterial effects, respectively.

Conclusion: Given the strong inhibitory capacity of L. plantarum and L. casei, particularly against antibiotic-resistant strains, postbiotics derived from these probiotics may offer a promising and safe alternative strategy for controlling resistant pathogens.