Antibacterial and Antibiofilm Screening of New Platinum(IV) Complexes with some S-Alkyl Derivatives of Thiosalicylic Acid

The interest in determining the influence of new metal complexes on microorganisms is increasing due to the growing pathogenic resistance. This investigation showed influence of 5 new Pt(IV) complexes on 16 strains of bacteria. Antibacterial activity was tested using microdilution method with resazurin while antibiofilm activity was observed by tissue culture plate method and antibiotic doxycycline was used as positive control. The results were expressed as minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and biofilm inhibitory concentration (BIC). The complexes were labeled as: C1 for Pt(S-bz-thiosal)₃, C2 for Pt(S-met-thiosal)₃, C3 for Pt(S-et-thiosal)₃, C4 for Pt(S-pr-thiosal)₃ and C5 for Pt(S-bu-thiosal)₃. The best result on Gram positive bacteria was obtained with C1 and MIC on Staphylococcus aureus ATCC 25923 was ˂7.81 μg/ml. Bifidobacterium animalis subsp. lactis (probiotic) was sensitive to C2 (MIC at 15.625 μg/ml). The best sensitivity on Gram negative bacteria was observed on Escherichia coli ATCC 25922 with C1, C2, C3 and C4, on Proteus mirabilis ATCC 12453 with C1, and on Pseudomonas aeruginosa with C2, C3 and C5 (all MICs at 250 μg/ml). The tested complexes were more efficient as antibiofilm agents and the best results were obtained with C2 acting against S. aureus and S. aureus ATCC 25923 biofilm.

In conclusion, we noticed that the tested compounds exhibited promising properties as antibacterial agents and antibiofilm agents,