Sphingosine and
sphinganine, free
sphingolipids of the stratum corneum, are, in vitro, strongly inhibitory for both bacteria and fungi. Whether or not they are suitable, indeed active, in vivo was examined: (i) on human volunteers, first as a preventative
antiseptic against subsequently applied Staphylococcus aureus and Candida albicans, and second as a restorative
antiseptic against the previously expanded normal skin flora; and (ii) on guinea-pigs as
therapy for experimental C. albicans and
Trichophyton mentagrophytes infections. In the
antiseptic studies, which involved 200 micrograms/cm2 of
sphinganine in
ethanol (50 microliters of a 1.6%
solution), up to three-log reductions in the population of target micro-organisms were obtained, compared with vehicle and untreated controls (P < 0.001). The daily application of
sphingosine as 1.5%
ethanol-
petrolatum ointment was able to diminish
inflammation slightly in dermatophyte-infected guinea-pigs (P = 0.02-0.05), although the animals remained culture positive over the 3-week sampling period. The
candida infections, treated daily with 1.5%
sphinganine in
ethanol, showed no improvement in
inflammation compared with controls, except for 2 days of the 2-week observation period (P = 0.01-0.03); however, by the fourth day of
therapy the yeast was eliminated in 75% of animals. No gross toxicity was observed among animals or human volunteers. These experiments further support simple
sphingolipids as important
antimicrobial agents of the cutaneous barrier and point toward a new biochemical approach in treating
infectious disease.