Isotretinoin may have transformative effect on skin microbiome

Isotretinoin alters the skin microbiome of patients with acne to more closely resemble that of people with normal skin. Study results suggest that isotretinoin creates a ‘bottleneck’ that selects beneficial communities of bacteria, creating a skin microbial community that reduces the chances of acne relapse, even when normal oil production returns to the skin after treatment is stopped.

“When you have a bottleneck, you create an opening for other microbes to move in and increase in abundance,” said Makedonka Mitreva, PhD, the study’s senior author and assistant director of the McDonnell Genome Institute at Washington University School of Medicine in St. Louis, in a press release published on Dec. 21, 2018. “We see this happening here. After the treatment, the microbial communities shift to a mix of populations that appears to be healthier, and that shift persists months after the treatment.”

Dr. William H. McCoy examines a patient with acne. Photo by Matt Miller.

According to the researchers, these findings also support the notion of developing alternative treatments for acne that feature less side-effects (Journal of Investigative Dermatology Oct. 24, 2018).

“Women often will go without treatment for acne during their pregnancies because there are not good therapies that are totally safe to use during that time,” said Dr. William H. McCoy, an instructor in the Division of Dermatology at Washington University School of Medicine in St. Louis, in a press release. “They need other options. Our study suggests there could be a way to provide some type of microbial ‘fertilizer’ or ‘weed killer’ on the skin to help promote the growth of healthy microbes. We are conducting a larger study to look more closely at these questions.”

Study methods

Researchers analyzed bacteria samples from facial skin swabs at four time points over a 10-month period. The samples came from 17 patients whose acne was treated with isotretinoin and eight untreated subjects. Of these eight, four had normal skin and four had acne.

Isotretinoin therapy increased the diversity of microbes found on the skin. Through DNA sequencing, investigators also identified four types of bacteria that bloomed with isotretinoin treatment. None had previously been associated with improved acne.

Isotretinoin also reduced the overall number of Propionibacterium bacteria, while it simultaneously increased the diversity of the individual types of the bacteria. Thirty-eight per cent of isotretinoin-treated patients did not show this beneficial pattern in the Propionibacterium communities. This percentage is similar to the proportion of isotretinoin-treated patients in other studies who needed additional rounds of therapy.

“. . . we also know that this medication does not work on the bacteria themselves. It changes the patient’s skin. So, if the microbes are changing, it is in response to changes in the patient’s skin. The drug appears to make the skin less hospitable to acne-causing bacteria,” said Dr. McCoy.

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