4.3. In Vitro Assessment of the Antimicrobial Activity of the Newly Synthesized F-Benzoylthiourea Derivatives on Planktonic Microbes (Grown in Suspension)

The inhibitory activity upon microbial growth was tested on Gram-positive (S. aureus ATCC 25923, E. faecalis ATCC 29212, B. subtilis ATCC 6633) and Gram-negative (E. coli ATCC 25922, P. aeruginosa ATCC 27853) bacteria and one fungal (C. albicans ATCC 10231) strain. The compounds were solubilized in DMSO to a final concentration of 10 mg/mL and further sterilized by filtration (using 0.22 µm filter membranes). The quantitative assay of the minimal inhibitory concentration (MIC, μg/mL) was performed by the microdilution method in 96 multi-well plates [59]. In this purpose, serial binary dilutions (ranging between 1024 and 8 μg/mL) were achieved in nutrient broth/YPG (yeast peptone glucose) and each well was seeded with microbial inoculum of 0.5 McFarland density. The plates were incubated for 24 hours at 37 °C in the case of bacterial strains, and 48 hours at 28 °C in the case of the fungal strain. The respective MIC values were reported as being the lowest concentration of the tested compound which inhibited the visible microbial growth.