Synthesis of benzoylthiourea derivatives and analysis of their antibacterial performance against planktonic Staphylococcus aureus and its biofilms

Following the appearance of several antimicrobial agents to control the spread of infections, two major challenges have emerged: 1- the occurrence and blowout of multiresistant bacteria and the increase of chronic diseases, and 2- difficult-to-eradicate infections. In this study, we tested five benzoylthiourea derivatives for their ability to inhibit and stop bacterial growth and evaluated the possible influence of 1,2,4-triazolyl-benzoylthiourea derivative 4 on the formation and eradication of S. aureus biofilms. Benzoylthiourea derivatives 4, 6, 10, 11, and 13 were obtained in one or two steps with low cost and subjected to tests to identify their minimum inhibitory concentration and minimum bactericidal concentration. In vitro tests were also performed to assess their effects on biofilm formation and in preformed biofilms and scanning electron microscopy was used to visualize the effects on biofilm formation. The 1,2,4-triazolyl-benzoylthiourea derivative 4 showed bacteriostatic activity against the Staphylococcus aureus HU25 clinical strain with an minimum inhibitory concentration (MIC) of 16 µg.mL-1 , which is below the toxic concentration (at 2,500 µg.mL-1 , 62.25% of the cells remained viable). Compound 4 also effectively prevented biofilm formation at the three subinhibitory concentrations tested (1/2 MIC, 1/4 MIC and 1/8 MIC) as confirmed by SEM. For breakdown of formed biofilms, the main influence was at a subinhibitory concentration (1/2 MIC). These findings make compound 4 a strong candidate for studies on the development of new antimicrobial and antibiofilm agents.