Formulation of 'idealized' topical antimicrobial mixtures for use with cultured skin grafts

In order to develop antimicrobial mixtures which provide broad-spectrum antimicrobial activity for use with cultured cell autografts, several individual antimicrobial agents, in concentrations non-toxic for cells in culture, were tested against a variety of bacteria and Candida spp. isolated from burn patients. An agar well diffusion topical assay was used. Antimicrobials active against Gram-positive and Gram-negative bacteria and antifungal agents, individually, were uniformly effective against their respective spectra of organisms. Broad-spectrum antibacterials were uniformly effective against Gram-negative bacteria but their activity varied against Gram-positive bacteria. Adding an agent active against Gram-positive bacteria to all broad spectrum antibacterial agents conferred uniform Gram-positive activity to the mixture. One mixture consisting of specific Gram-negative, Gram-positive and broad spectrum antibacterial agents, was uniformly active against all bacteria tested and the addition of antifungal agents extended the activity to cover Candida spp. without interfering with the mixture's overall antibacterial activity. Another mixture showed either additive or antagonistic activities against the battery of microorganisms tested. Thus, these methods can be used to identify mixtures of antimicrobials, in concentrations non-toxic for cells in culture, that have very broad spectra of antimicrobial activity. Such mixtures should be evaluated in patients when cultured skin grafts are used.