In vitro Antibacterial Evaluation of Newly Synthesized Heterocyclic Compounds Against Streptococcus Pneumoniae

In recent years, the spread of drug-resistant strains of Streptococcus pneumoniae, as the most common causes of bacterial respiratory infections, threatens public health. Therefore, the use of new antimicrobial medicines to inhibit this pathogen is an urgent demand. In this research project, the inhibitory effects of thirty recently synthesized compounds including thiazole, thiazolidine, imidazole, tetrahydropyrimidine, oxazolidine and thiazepine derivatives against this bacterium have been studied as well. The broth microdilution method was used to determine the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC), zone diameters of bacterial growth inhibition were also measured by a disk diffusion method. All the obtained results were compared with antibacterial effects of gentamicin and penicillin antibiotics. Among all investigated compounds, only derivatives 3d, 5a, 5b, 7, 9c, 15, 17c and 17d showed inhibitory effects against S. pneumonia. As a result, the most and least effects respectively belonged to thiazole derivative 15 and thiazepine derivative 17c with zone diameters of bacterial growth inhibition= 20.2, 9.3 mm, MIC= 64, 2048 μg/mL and MBC= 128, 4096 μg/mL. Whereas thiazole derivative 15 exhibited a good inhibitory activity against the mentioned pathogen, it can be replaced as a good agent instead of antibiotics.