Abstract

Isotretinoin, a retinoid – can be used to treat patients with moderate to severe acne despite the adverse effects of mucosal surface drying and the contraindication of use during pregnancy. In clinical practice, patients are frequently prescribed systemic isotretinoin because they have not responded to previous treatment with oral or topical antibiotics. Broad-spectrum antibacterial therapy attempts have nevertheless promoted changes in the diversity and antibiotic resistance status of the patients’ skin microbiota. The present study investigated the recovery and analysis of skin organisms from 53 patients (mean age 23y range 15-37y) before, during and after treatment with a 16-week course of isotretinoin (1mg/kg body weight). The number of aerobic bacterial isolates (presumptive Staphylococci) recovered from Baird-Parker agar from each of three specific sites per patient were compared with age-matched controls of healthy volunteers. Both patients and controls had generally similar numbers of organisms on the nares, cheek and toe webs before treatment, whereas all patients showed a significant reduction in Staphylococci recovered from one site during and after 16 weeks of isotretinoin treatment. The majority of the patients had a greater reduction (1-2 log) for the cheek site than either nares or toe webs both of which showed minimal reduction. Preliminary results from this study show a pronounced reduction in the number of presumptive staphylococci recovered from the treated group immediately following isotretinoin compared to untreated controls. Since isotretinoin has little known antibacterial activity against the Staphylococci the observed reductions would suggest that the effect is mediated through changes in the skin nutritional micro-environment.