Background and Research on Copper Alloys as an Antimicrobial Surface and the CusB protein of the Copper-Transporting Efflux System CusCFBA

Abstract

Bactericidal properties of copper surfaces have been investigated in search of selfsanitizing materials in food and healthcare industries. However, bacteria in these environments are rapidly acquiring antibiotic and heavy metal resistance, which is thought to be a co-selection process (Baker-Austin, 2006). Copper-resistant strains of Escherichia coli and Enterococcus faecium isolated from pigs fed copper sulfate were examined (Hasman, 2002). Survival of strains was tested by timed incubation on onesquare- inch copper alloys with varying degrees of moisture during inoculation of the surfaces. Results showed rapid killing of E. coli and E. faecium copper-resistant strains when samples were spread in a thin layer on alloys with 85 % or greater copper content. E. coli strains had short survival rates under dry conditions while E. faecium strains were less affected. Dry or wet inoculations had no effect on the survival rates on stainless steel, since strains survived equally and no die-off was seen. Re-inoculation with E. coli on the alloys every 3 hours over a 24-hour period showed no CFUs remaining at each time point tested while bacteria survived without reduction of CFUs on the stainless steel controls after 24 hours. Results indicate that the bactericidal properties of metallic copper surfaces can be effective in killing copper-resistant strains of E. coli and E. faecium.