Organisms associated with gram-negative folliculitis: in vitro growth in the presence of isotretinoin.

Isotretinoin has been found to be effective in the treatment of Gram-negative folliculitis. We investigated the direct in vitro antibacterial activity of isotretinoin against Gram-negative species. The concentrations of isotretinoin tested were two and ten times greater than the maximal levels attained in the sera of patients receiving oral isotretinoin. Regardless of the inoculum size, each organism tested grew as well in isotretinoin-containing media as it did in the control medium. These findings suggest that the efficacy of isotretinoin in patients with Gram-negative folliculitis is due to mechanisms other than direct antimicrobial action.