Each year, up to 50 million people in the United States are affected by acne, making it the most common skin condition in the country. In a new study, researchers have uncovered new information about the causes of acne, which could change the way the condition is treated.

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Researchers identified differences in strains of P. acnes between people with and without acne.

Study leader Dr. Huiying Li, of the David Geffen School of Medicine at the University of California-Los Angeles (UCLA), and colleagues suggest that acne may not be caused by the presence of a specific strain of bacteria.

In their study, the researchers uncovered evidence that the balance of bacteria on the skin may play a key role in acne development.

Dr. Li and team recently presented their findings at the Microbiology Society's 2017 annual conference, held in the United Kingdom.

Acne is a chronic, inflammatory skin disease characterized by the development of papules, blackheads, whiteheads, nodules, cysts, and other types of pimples.

The areas of the body most affected by acne are the face, neck, chest, shoulders, and back. This is because these areas have high numbers of sebaceous glands. These are glands in the skin follicles that produce sebum - an oily substance that lubricates the hair and skin.

Sometimes, however, too much sebum is produced. This can clog the pores, creating a desirable environment for bacteria to thrive, which can lead to inflammation and acne development.

The bacterium Propionibacterium acnes is considered a key player in acne development. Studies have shown that P. acnes uses sebum as a source of energy, and its presence in the pores initiates an immune response that triggers inflammation.

However, P. acnes is highly abundant in the pores of individuals with and without acne, which indicates that it is not simply the presence of this bacterium that drives the skin condition.

P. acnes makeup differs in people with acne

For their study - which has also been published in the journal Scientific Reports - Dr. Li and colleagues sought to learn more about the role of bacteria in acne development.

The team enrolled 72 adults to their study, of whom 38 had acne and 34 did not. Using over-the-counter pore cleansing strips, the researchers collected skin follicle samples from each participant.

Next, the team used a method known as DNA shotgun sequencing in order to determine the makeup of skin microbiota for each individual.

On comparing the skin microbiomes of individuals with and without acne, the researchers identified some differences in strains of P. acnes.

They found that adults without acne possessed P. acnes abundant with genes that are associated with bacterial metabolism. Such genes are believed to be involved in halting the colonization of harmful bacteria in the skin.

However, adults with acne had higher levels of virulence-related genes in P. acnes, the team reports. These included genes linked to the production of bacterial toxins that promote inflammation and poor skin health.

Using the identified differences in P. acnes between the two groups, the team was able to accurately predict the presence of acne.

"This study suggests that the makeup of the bacteria in the follicles can reflect, as well as influence, the skin condition in acne or healthy skin," says Dr. Li.

Results could lead to personalized acne treatments

According to the researchers, their study sheds light on the underlying mechanisms that drive the development of acne, which could lead to targeted treatments for the common skin condition.

Such treatments could include probiotics that target specific strains of bacteria, the team suggests.

"Understanding the bacterial community on the skin is important for the development of personalized treatments in acne.

Instead of killing all bacteria, including the beneficial ones, we should focus on shifting the balance toward a healthy microbiota by targeting harmful bacteria or enriching beneficial bacteria."

Study co-author Dr. Emma Barnard, David Geffen School of Medicine, UCLA

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