Antimicrobial activities in vitro and in vivo of transition element complexes containing gold(I) and osmium(VI)

Metal compounds have been used as antibacterial agents for centuries. The in-vitro activity of two metal containing complexes, one gold, the other osmium, was investigated using a panel of clinically isolated bacteria and Candida albicans. Twenty strains of each organism were used and MIC and MBC values determined using the agar plate dilution method. Protein binding effects on the activity of the compounds were also investigated using media supplemented with 5% human blood. In-vivo activity of the two compounds was subsequently determined in a hairless-obese mouse skin-surface activity model. Both compounds were highly active against the Gram-positive organisms and Candida albicans in vitro. The gold compound had some Gram-negative activity but the osmium complex was inactive against these organisms. Both were extensively protein bound. In the in-vivo experiment the gold compound achieved a 2-3 log reduction for all the test organisms and was at least as good as or superior to mupirocin in its eradication rate. The osmium compound was inactive.