Clinical investigation of topical antimicrobials in healthy volunteers

OBJECTIVE: To evaluate the antibacterial activity, onset of action, and duration of action of four topical antimicrobial gels containing cetrimide, bacitracin, polymyxin B sulfate, and a placebo gel. DESIGN: Multiples (1 x, 2x, 4x, 8x) of minimally inhibitory in vitro drug concentrations were formulated in a gel vehicle. Antibacterial activity was evaluated using a scrub-wash methodology on artificially inoculated skin over an 8-hour study period. SETTING AND PARTICIPANTS: Healthy volunteers with intact forearm skin participated in the study. A standardized culture of Staphylococcus aureus NCTC 6571 was applied to four areas on each forearm, randomly assigned topical treatments were applied, and sites were sampled at predetermined time intervals using a surfactant wash fluid. OUTCOME MEASURES: Recovered bacteria were quantitated, allowing a comparison of antibacterial activity. RESULTS: Two-way and one-way ANOVA and a Scheffe test confirmed significant differences in antibacterial effect between the formulations containing 4 and 8 times the minimally inhibitory in vitro concentrations and placebo (p < 0.05). Duration of action was similar for all preparations; however, onset appeared to be faster with the formulations containing 4 and 8 times minimally inhibitory in vitro concentrations. CONCLUSIONS: The two topical preparations containing 4 and 8 times the minimally inhibitory in vitro concentrations of cetrimide, bacitracin, and polymyxin B sulfate demonstrated significant antibacterial activity and may have potential for further clinical investigations.