Resistance of antimicrobial skin preparations to saline rinse using a seeded bacteria model

Objective We describe a randomized blinded study to evaluate the antimicrobial persistence following saline exposure of 2 commercially available skin antiseptic agents. One agent contained iodine povacrylex in alcohol and the second contained chlorhexidine gluconate in alcohol. Method Both agents were applied to the forearms of 36 healthy subjects according to manufacturers' instructions and allowed to dry. The sites were then exposed to either a saline rinse or to a saline-saturated gauze, similar to the challenges that preps would face during most surgical procedures. Two analyses were performed: (1) An indicator organism was seeded onto the treated sites. After 30 minutes, samples were collected from the treated sites and surviving bacterial colonies were enumerated and log reductions calculated. (2) The saline-saturated gauze was analyzed chemically for presence of chlorhexidine or iodine. Results The baseline densities (stated as logarithms of colony forming units “log CFU”) of the sites to which the agents were applied had statistically equivalent microbial densities. Both agents reduced the density of organisms in a statistically significant manner. Chemical analysis of the gauze samples indicated that 35 of 36 samples had detectable chlorhexidine while no samples had detectable iodine ( P < .0001). Conclusion The results indicate that chlorhexidine is removed by saline-soaked gauze while the iodine povacrylex water-insoluble film remains intact under the same conditions. The implication is that similar results may occur in surgery when saline is used.