Effects of Synthetic Retinoids on the Growth of Bacteria and Their Susceptibility to Antibiotics

Summary

In patients treated with oral retinoids the recovery of Propionibacterium acnes and other anaerobic bacteria in the skin is markedly reduced, whereas an increased colonization of the skin and a significant rise in the incidence of cutaneous staphylococcal infections are observed. Since very little is known about the effects of retinoids on bacteria, in the present study we investigated the influence of 4 retinoids (isotretinoin, etretinate, arotinoid ethyl ester, arotinoid sultane) in 15 different concentrations on the growth of 10 Gram-positive and Gram-negative bacteria in vitro and on their susceptibility to 10 antibiotics.

It was found that all retinoids were not capable of affecting either the growth of bacteria or their susceptibility to antibiotics. It seems reasonable, therefore, to assume that the retinoid-induced changes in cutaneous bacterial flora in vivo are due to mechanisms other than to the direct action of these compounds on bacteria.

Key Words:

• retinoids
• skin flora
• antibiotics