Antimicrobial resistance represents a major and growing challenge in both medicine and food industry, highlighting the need for alternative antimicrobial strategies. The aim of this work was to evaluate the antimicrobial activity of selected natural compounds (cinnamaldehyde, citric acid, caffeine, linalool, and nisin) against model Gram-positive (Enterococcus faecalis, Listeria innocua, Staphylococcus aureus, Streptococcus parasanguinis) and Gram-negative bacteria (Enterobacter cloacae, Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica Typhimurium). Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) were determined using the broth microdilution method and using reagents such as resazurin and BacTiter-Glo, while bacterial growth and metabolic activity were monitored by measuring optical density. Growth kinetics were further analysed using growth curve modelling with programmes QurvE and Excel. The results demonstrated that the effectiveness of the tested compounds varied depending on the bacterial species, with cinnamaldehyde exhibiting the strongest antimicrobial activity, whereas bacteria Pseudomonas aeruginosa showed the highest level of resistance. The tested compounds primarily affected bacterial growth by prolonging the lag phase, reducing the maximum growth rate, and decreasing the final cell density. The findings confirm the potential of natural antimicrobial compounds as alternative or complementary approaches to conventional antimicrobial strategies and contribute to a better understanding of their role in addressing the increasing issue of antimicrobial resistance.
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