Comparison of two in vivo and two ex vivo tests to assess the antibacterial activity of several antiseptics

Abstract

An ex vivo test was adapted to mimic the in vivo conditions of testing antiseptic activity on human forearms and in the European Standard Hygienic Handwash Test (BSEN 1499). The study was to validate the ex vivo protocols using 4.8% (w/v) para-chloro- meta-xylenol (PCMX, neat Dettol), 0.5% (w/v) triclosan in 70% (v/v) isopropanol, and 2% (v/v) povidone-iodine against a high bacterial inoculum (>10 8 cfu/mL) of Escherichia coli NCTC 10538. Two ex vivo tests using human skin samples, including one introducing a mechanical rubbing effect, were compared with two corresponding in vivo tests (the forearm test and the BSEN handwashing test). All antiseptics assessed in vivo (forearm and handwash tests) produced reductions in bacterial counts that were significantly greater than those for the non-medicated soft soap control. When assessed ex vivo without rubbing, only PCMX and povidone-iodine achieved reductions significantly greater than soft soap. When assessed ex vivo with mechanical rubbing, only PCMX and triclosan achieved reductions significantly greater than soft soap. Overall, the antiseptics at the concentrations tested were more active when tested in vivo than ex vivo. The addition of a mechanical effect, either in vivo by the volunteers washing their hands or ex vivo by a drill rubbing two skin samples against each other, produced a significantly greater reduction in bacterial concentrations. The ex vivo tests were easily adapted to mimic in vivo protocols. The value of such tests, particularly the one that includes a rubbing effect, may be significant as they avoid the need for human volunteers.