New thioureides of 2-(4-methylphenoxymethyl) benzoic acid with antimicrobial activity

The purpose of this study was to evaluate in vitro, by means of qualitative and quantative methods, the antimicrobial activity of some new synthesized chemical compounds previously solubilized in DMF (Dimethyl formamide). The qualitative screening of the susceptibility spectra of different microbial strains versus these compounds was performed by three adaptated 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 previously inoculated with microbial suspension. The quantitative assay of the antimicrobial activity was performed by broth microdilution method in 96-well microplates in order to establish the minimal inhibitory concentration (MIC).The antimicrobial activity was tested against Gram-positive strains (Staphylococcus) aureus sp., Bacillus subtilis sp.), Gram-negative (Escherichia coli sp, Pseudomonas aeruginosa sp., Klebsiella pneumonia sp.) and fungal strains (Candida albicans sp, Aspergillus nige rsp.). All tests were performed by comparison with the reference strains: K. pneumoniae IC 13420, E. coli IC 13529, S. aureus IC 13204, P. aeruginosa IC 13202, B. subtilis IC 12488, C. albicans IC 249, A. niger IC 13534. Our results indicated that the tested compounds exhibited specific antimicrobial activity, the highest activity being noticed against planktonic fungal cells (MIC ranging from 62.5 microg to 15.6 microg), followed by P. aeruginosa (MICs from 250 microg to 31.5 microg). Only few compounds exhibited antimicrobial activity against E. coli and K. pneumoniae. Antimicrobial activity against Gram positive bacteria was noticed for the most of the tested compounds, five of them exhibiting very low MIC values (MICs from 1000 microg to 62.5 microg).