Gold, Platinum and Palladium Ions Demonstrate Strong Antimicrobial Action Against Hospital Pathogens with Reduced Effect in the Presence of Bovine Plasma Soil.

AIMS: The antimicrobial efficacy of five metal ions (silver, copper, platinum, gold, palladium) was assessed against Klebsiella pneumoniae, Acinetobacter baumannii and Enterococcus faecium in the presence and absence of a bovine plasma soil. Changes in the elemental structure of the bacteria were identified. METHODS: Planktonic and biofilm inhibition assays were carried out in the absence and presence of a 10% bovine plasma soil. Elemental changes to the bacteria were determined using Energy Dispersive X-ray Spectroscopy (EDX). RESULTS: The reduction in planktonic bacteria without soil was 8-log at 0 h for gold and palladium ions, and with soil, platinum demonstrated a 7-log reduction at 4 h against K. pneumoniae and A. baumannii. For E. faecium with and without soil, a 4-log reduction at 24 h with silver ions was demonstrated. Reduction of biofilm without soil was 88.8% against K. pneumoniae (platinum) 91.2% (gold) against A. baumannii and 82.3%-82.9% (platinum/palladium/gold) against E. faecium. With soil, biofilm reduction for K. pneumoniae or A. baumannii with gold ions was 82.3% and with gold ions against E. faecium 25.5%. Elemental changes following metal ion treatment could be indicative of cellular damage but did not always correlate with the antimicrobial activity. In the presence of the soil, a decrease in the antimicrobial efficacies was demonstrated and fewer elemental changes were detected. CONCLUSIONS: Platinum, palladium and gold ions were the most effective antimicrobials. Across all three tested genera, soils reduced the antimicrobial activity.