Antibacterial activities of 5-nitro-2-furyl and 5-nitro-2-imidazolyl derivatives of 1,3,4-thiadiazole

Background and Aims: Nitrofurans and nitroimidazoles are broad spectrum antimicrobial agents which affect the microbial DNA. The aims of the present study were to evaluate the new derivatives of these two groups against certain Gram positive and Gram negative bacterial strains. Materials and Methods: Seven new derivatives of nitrofuran and nitroimidazoles were synthesized and 6.4 mg of each derivative were dissolved in dimethyl sulfioxide. Then, 8 serial dilutions of agents were prepared as 0.5, 1, 2, 4, 8, 16, 32 and 64 μg/ml using Muller-Hinton broth and minimum inhibitory concentration (MIC) for each derivative was measured and compared to ciprofloxacin as a standard. Results: All derivatives had no antibacterial effects against Gram negative bacteria (MIC > 64 μg/ml) and just 2-(5-nitro-2-furyl)-5-(n-pentylsulfunyl)-1,3,4-thiadiazole had mild antibacterial effects against Klebsiella pneumonia (MIC of 16-32 μg/ml). The antibacterial effects of derivatives against Gram positive bacteria also showed variations from completely inhibited the growth of Staphylococcus epidermidis and Bacillus subtilis (MIC < 0.5 μg/ml) by 2-(5-nitro-2-furyl)-5-(n-buthylthio)-1,3,4-thiadiazole to no inhibition of S. epidermidis and streptococcus pyogenes. Conclusions: These compounds have weak antibacterial effects and just two of them showed antibacterial effects quite similar to that of positive control.   Keywords: Nitrofuran, Nitroimidazole, minimum inhibitory concentration, ciprofloxacin.