INVESTIGATION OF ANTIBACTERIAL ACTIVITIES OF SOME ACYL THIOUREA DERIVATIVES AGAINST ESCHERICHIA COLI AND KLEBSIELLA ORNITHINOLYTICA

ABSTRACT This study investigated the antibacterial activities of five acyl thiourea derivatives, labeled A1, A2, A3, A4, and A5, against Escherichia coli and Klebsiella ornithinolytica using antibacterial sensitivity testing (AST), minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) tests. The aim was to evaluate the potential of these compounds as new antimicrobial agents to address bacterial infections. The statement of the problem arose from the growing concern over antibiotic resistance, which threatens effective treatment of bacterial infections, necessitating the exploration of new antimicrobial agents like acyl thiourea derivatives. The justification for this study lies in the urgent need to develop alternative compounds to combat resistant strains, leveraging the potential of these derivatives based on their chemical properties. The AST results showed A1 produced zones of inhibition (ZOI) of 15 mm against E. coli and 18-19 mm against K. ornithinolytica, indicating sensitivity. A2 had no effect on E. coli (ZOI of 0 mm) but stopped K. ornithinolytica with ZOIs of 20-18 mm. A3 worked well against both, with ZOIs of 21-16 mm for E. coli and 21-18 mm for K. ornithinolytica. A4 showed no activity against E. coli (ZOI of 0 mm) but had the largest ZOI of 27 mm against K. ornithinolytica. A5 had no effect on K. ornithinolytica (ZOI of 0 mm) but stopped E. coli with ZOIs of 20-18 mm. The MIC tests revealed A1 and A4 had MICs above 20 mg/mL for both bacteria, A2 stopped K. ornithinolytica at 10 mg/mL, A3 stopped E. coli at 1.25 mg/mL and K. ornithinolytica at 5 mg/mL, and A5 stopped E. coli at 10 mg/mL. The MBC tests showed A1, A2, A4, and A5 needed 20 mg/mL to kill, while A3 required 20 mg/mL for E. coli and 10 mg/mL for K. ornithinolytica. The findings supported the claim of significant antibacterial activity, particularly from AST results, but highlighted challenges with high MIC and MBC values, suggesting a bacteriostatic rather than bactericidal effect. A4 showed promise against K. ornithinolytica, and A3 and A5 were effective against E. coli, with strain-specific actions noted. Limitations included a narrow concentration range, incomplete data for some bacteria, and lack of stability tests. Recommendations include extending MIC/MBC ranges, testing both bacteria fully, using replicates, modifying structures, combining with antibiotics, assessing stability, and exploring other bacterial strains to enhance antimicrobial development. This study lays a foundation for improving these compounds as potential treatments to address antibiotic resistance.