Laboratory and in-vitro testing of skin antiseptics: a prediction for in-vivo activity?

Bacteria-laden skin squames, detached bacterial clumps and isolated bacteria floating in skin fluids are the major infective units in hand and skin transmission of microorganisms. These units have differing ability to colonize new surfaces and may have different susceptibility to antiseptics. MIC-MBC testing on isolated bacteria serves to confirm the expected susceptibility of particular isolates and is useful for surveillance of the evolution of antiseptic resistance; however, it is often unreliable in predicting the in-vivo effect. In-vitro tests aimed at duplicating natural conditions (including the effect of antiseptics on bacterial biofilms, or better, on the different infective units) are under evaluation. Meanwhile, tests involving natural skin surfaces, like the Story test, offer reproducible and useful data.