Antimicrobial activity of some new 2-thiophene carboxylic acid thioureides

The aim of this study was to evaluate the in vitro antimicrobial activity of some newly synthesized 2-thiophene carboxylic acid thioureides. The qualitative screening of the susceptibility spectra of different microbial strains to these compounds was performed by three adapted diffusion methods: paper filter disk impregnation with the tested substances solutions, the disposal of tested solutions in agar wells and the spotting of tested solutions on solid medium seeded with microbial inoculums. The in vitro antimicrobial testing was performed by binary microdilution method, in 96 multiwell plates, in order to establish the minimal inhibitory concentration (MIC) against Gram-positive: Staphylococcus aureus, Bacillus subtilis, Gram-negative: Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, as well as Candida albicans and Aspergillus niger, using both reference and clinical, multidrug resistant strains. All the tested compounds were active against reference strains, but also against Gram-negative clinical strains MIC, ranging from 250 to 31.25 μg/mL. All tested compounds exhibited antifungal activity MIC ranging from 62.5 to 31.25 μg/mL. As concerning the Gram positive strains, all tested compounds presented antimicrobial activity against Bacillus subtilis (MIC from 125 to 7.8 μg/mL), but for multi-drug resistant Staphylococcus aureus the MIC values were higher (MIC from 500 to 125 μg/mL).