Microbe imbalance fuels acne

Dr. LiThe difference between acne and healthy skin is largely dependent on the balance of the skin microbiota, according to study results presented in April at the Microbiology Society Annual Conference held in Edinburgh, United Kingdom.

The study was published in December 2016 in the journal Scientific Reports.1

“The bacterium Propionibacterium acnes has been thought to play an important role in acne pathogenesis,” says senior author Huiying Li, PhD, an associate professor of molecular and medical pharmacology at the David Geffen School of Medicine at University of California, Los Angeles. “However, P. acnes is necessary for skin health.”

The study suggests that the balance of the skin microbial community on the face affects whether a person develops acne or remains in a healthy state.

“It is not just the presence or absence of a particular strain, but the balance of all the microbes in the skin microbiome,” Dr. Li says.

Present in every subject

The investigators analyzed skin samples from 72 individuals: 38 had acne and 34 did not. “We examined facial skin follicle samples, since these are the sites at which acne originates,” Dr. Li says.

Using a method known as shotgun metagenomic sequencing analysis, the researchers identified differences in the microbial compositions of the skin microbiome between the two groups.

“We found that the major skin bacterium, P. acnes, was present in every subject, regardless of whether or not they had acne,” Dr. Li says.

Healthy individuals had a slightly higher relative abundance of P. acnes in the skin microbiome compared with its occurrence in acne patients: 93.8% versus 88.5%.

In addition, a closely related bacterial species, Propionibacterium granulosum, was significantly more abundant in healthy individuals than in acne patients.

The investigators also analyzed the composition of the skin microbiome in older healthy individuals and found it to be similar to that of their younger counterparts.

By examining the functional abilities of P. acnes in the healthy and acne-patient groups, the study found that virulence-related genes involved in the production and transport of bacterial toxins were more abundant among acne patients.

Conversely, other genes, including those involved in bacterial growth and development, were more enriched in the skin microbiome of healthy individuals.

Reliable markers

The researchers demonstrated that the skin microbiome profile could be used to predict the clinical status of the skin with high accuracy (85%), despite the fact that acne is a multi-factorial disease, in which host factors - including hormones and genetic factors, as well as other environmental factors - may play a role.

The researchers further validated prediction based on the skin microbiome, with similar prediction accuracy, in an additional 10 individuals.

The study authors believe that developing reliable markers based on the skin microbiome could aid clinicians in choosing appropriate acne treatment regimes. The microbiome markers could improve diagnosis, skin-health monitoring, and disease prognosis.

It is believed that P. acnes offers health benefits to the skin by producing short-chain fatty acids (SCFA) and maintaining a low skin pH. SCFA contains antimicrobial properties that contribute to the acidic pH of the skin in warding off pathogens. Disrupting normal skin pH is associated with several skin diseases, including acne.

The benefits of propionibacteria in the skin microbiota mirror the results of skin microbiome studies of other skin diseases, such as atopic dermatitis and psoriasis. In those studies, the abundance of propionibacteria was reduced in the diseased state, but increased after treatment.

The microbiome can contribute as well as reflect the skin’s health, according to Dr. Li. “However, if you try to kill all the P. acnes, this is not good for the skin. You need good strains of P. acnes, which are beneficial to our skin’s health,” she says. “The goal is to restore the balance of the skin microbiome, such as by potential topical probiotic treatment or phage therapy, which can be more specific and targeted than antibiotics. Antibiotics can kill both harmful and beneficial skin bacteria non-selectively.” ƒ

Disclosure: Dr. Li reports that she is co-founder of SkinomiX Biosciences Inc. and a shareholder of Naked Biome Inc.

Reference: Barnard E, Shi B, Kang D, Craft N, Li H. The balance of metagenomic elements shapes the skin microbiome in acne and health. Sci Rep. 2016;6:39491.