We aimed to investigate the antibacterial and antibiofilm effects of turmeric and chitosan against the planktonic and biofilm forms of multidrug-resistant (MDR) bacteria. A group of MDR bacteria, including clinical isolates of methicillin-resistant Staphylococcus aureus, carbapenem-resistant Pseudomonas, carbapenem-resistant Enterobacteriaceae and AmpC-producing Enterobacteriaceae, were collected by phenotypic and genotypic assays. The broth microdilution method was used to investigate the MIC of turmeric aqueous extract and chitosan. To investigate the synergistic effect of the combination of these natural compounds, we used the checkerboard assay. According to the results of this study, turmeric and chitosan showed inhibitory effects on MDR bacteria, especially on the planktonic form of methicillin-resistant S. aureus as a Gram-positive compared to tested Gram-negative bacteria (carbapenem-resistant Pseudomonas, carbapenem-resistant Enterobacteriaceae and AmpC-producing Enterobacteriaceae). The antibiofilm effect of turmeric and chitosan was found more often in carbapenem-resistant Pseudomonas isolates. There was no significant difference between the tested Gram-negative bacteria because most of the tested strains were inhibited in 512 and 1024 μg/mL concentrations of chitosan and turmeric aqueous extract. In this study, turmeric aqueous extract and chitosan exhibited significant antibacterial and antibiofilm properties. However, the effect of these compounds should be investigated using in vivo models for use in pharmaceutical and disinfectant formulations.

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