Assessment of the potential for microbial resistance to topical use of multiple antimicrobial agents

The goal of this study was to reduce the likelihood of the generation and/or persistence of bacterial resistance to some antimicrobial components contained in a topical antimicrobial mixture (neomycin, polymyxin B, mupirocin and ciprofloxacin) for use with cultured skin grafts, by substitution of alternative antimicrobials, specifically fusidic acid for mupirocin and ofloxacin for ciprofloxacin. The alternative agents failed to serve that purpose. However, with the exception of specific genera of bacteria, Proteus sp. and Providencia stuartii, 90% or more of all other bacteria tested were susceptible to the action of one or more of the individual antimicrobial agents contained in the original mixture. This was true when bacteria were highly susceptible to the antimicrobials, generally, or when bacteria resistant to specific antimicrobials such as penicillin-class antibiotics and ciprofloxacin, were tested. These results suggest that the redundancy of antimicrobials contained in this mixture reduces the chance that resistant bacteria generated by the use of this mixture or already present on wounds would persist when the mixture is used clinically.