Evaluation of activity and potential for development of antimicrobial resistance to a new tinted 2% chlorhexidine gluconate/70% isopropyl alcohol film-forming sterile preoperative skin preparation

•A new chlorhexidine gluconate skin prep with a film-forming copolymer was developed and tested in vitro.•The copolymer did not compromise the antimicrobial efficacy.•No potential for development (emergence) of resistance was observed.•No cross-resistance with antibiotics was observed. Chlorhexidine gluconate (CHG) is routinely used for skin antisepsis before surgery. Its activity may be affected by formulation ingredients and the presence of organic matter such as blood and proteins. This in vitro study was designed to evaluate the antimicrobial activity of a new CHG skin prep containing a film-forming copolymer, and detect its potential for developing resistance and the potential for cross-resistance to antibiotics after CHG exposure. Antimicrobial activity was evaluated in the presence and absence of serum in an in vitro time-kill study. Emergence of resistance to CHG and cross-resistance with antibiotic procedures were performed in vitro using 10 repository isolates from eight species and eight clinical isolate strains equal to the repository isolate strains (four isolates, two resistant and two non-resistant per species). A 5 log10 reduction (99.999%) for all organisms was observed using the copolymer formulation. The activity remained unchanged in the presence of serum. The minimum inhibitory concentration (MIC) did not increase for any of the strains evaluated for emergence of resistance. In addition, there was no change in MIC related to cross-resistance observed for any of the organism/antibiotic combinations tested. These results suggest that the film-forming copolymer and the tint in the new CHG skin prep did not interfere with antimicrobial efficacy, even in the presence of an organic soil load, and that the tested formulations showed no potential for developing resistance or cross-resistance with antibiotics.