Antifungal activity of organotin compounds with functionalized carboxylates evaluated by the microdilution bioassay in vitro

We investigated the susceptibility of 96 well-characterized strains of yeast-like and filamentous fungi towards new organotin compounds: (1) [Sn(C4H9)(3)(OOCC6H4SO3H-2)], (2) Sn(C4H9)(3){OOC(CH2)(3)P(C6H5)(3)}]Br, and (3) [Sn(C6H5)(3) [OOC(CH2)(3)N(CH3)(3)}] Cl. In the case of yeast-like fungi, the in vitro susceptibility tests were carried out according to the Clinical Laboratory Standards Institute (CLSI, formerly NCCLS) reference method M27-A2, while for filamentous fungi the investigations were conducted according to the M38-A and M38-P methods. The organotin complexes 1, 2 and 3 are active antifungal agents. Minimal inhibitory concentrations (MIC) were in the range of 0.25-4.68 mu g/ml for all tested fungal strains. Considerably larger differences were found for minimal fungicidal concentrations (MFC). In the case of yeast-like fungi, the fungicidal effect was generally observed at organotin compounds concentrations of 2.34-9.37 mu g/ml. The MFC values for filamentous fungi were considerably higher and were in the range of 18.74-50 mu g/ml. In conclusion, organotin compounds 1, 2 and 3 showed high fungistatic and fungicidal activities against different species of pathogenic and nonpathogenic fungi. However, they were also highly cytotoxic towards two mammalian cell lines.