Antibacterial efficacy of Fabry's tinctura on the resident flora of the skin at the forehead. Study of bacterial population dynamics in stratum corneum and infundibulum after single and repeated applications.

The in-vivo antibacterial activity of Fabry's tinctura (FT), a 3 w% salicylic acid, 1 w% phenoli liquefacti containing 50 v/v% isopropanol used in dermatology for the treatment of erythrasma, pityriasis versicolor, acne vulgaris a.o. on the human resident skin flora was assessed by a new test method in comparison to 60 v/v% isopropanol. The test method consists of a detergent scrub method (DSM) in combination with the cyanoacrylate method (CAM) thus allowing the quantitative determination of bacterial densities in two depth compartments of human skin, separately for bacterial genera. The most important innovation of this test method is that its arrangement, especially the separate evaluation of the genera of the resident flora, makes it possible to examine the ability of an antimicrobial agent to invade different depth compartments by its bioactivity against the resident flora and to measure short-and-long-term efficacies under physiological conditions. Our findings in 120 volunteers indicate that compared to 60% isopropanol FT is able to reduce bacterial density in superficial and deep skin compartments immediately after a single application equally well, but for a significantly longer period. In repeated applications, 60% isopropanol does not produce a cumulative or long-lasting effect, but it causes an abundant rebound growth of Propionibacterium spp. in the lower skin compartment. FT, however, shows a cumulative antibacterial effect at the surface and in the depth persisting up to four days after the last application. It is concluded that by its salicylic acid and phenolic content FT is an effective drug for the topical antimicrobial therapy of skin diseases.