Everyone has acne-causing bacteria living on their skin, but researchers at the Washington University School of Medicine have identified that there are "good" and "bad" strains of the bacteria, which determine the frequency and severity of developing pimples.

The findings, which were published in the Journal of Investigative Dermatology, reveal that not all acne bacteria trigger pimples, they even identified one strain that can actually help maintain healthy skin.

Little is known about the scientific causes of acne, a disease which affects close to 80 percent of Americans - at least once in their lives. The treatment options have remained the same over the past few decades, with much need for improvement. A report in The Lancet said that further research is urgently needed for effective non-antibiotic treatments for acne, given the concerns of long-term antibiotic use and bacterial resistance.

Lead author of the study, Huiying Li, PhD, said:

"We hope to apply our findings to develop new strategies that stop blemishes before they start and enable dermatologists to customize treatment to each patient's unique cocktail of skin bacteria."

Propionibacterium acnes is a tiny microbe that lives in the oily region of the skin's pores. The bacteria can aggravate an immune response which causes red, swollen bumps to develop on the skin (acne).

The researchers collected samples of P. acnes from the noses of 49 pimply people and 52 people with clear skin. They extracted the microbial DNA from the strips and tracked a genetic marker to identify the bacterial strains.

They sequenced the genomes of 66 different P. acnes strains, which allowed them to analyze the genes in each of the strains.

Co-author of the study, George Weinstock, PhD, professor of genetics at Washington University in St. Louis, said:

"Our research underscores the importance of strain-level analysis of the world of human microbes to define the role of bacteria in health and disease. This type of analysis has a much higher resolution than prior studies that relied on bacterial cultures or only made distinctions between bacterial species."

The investigators were specifically looking for any differences in the bacterial strains of those suffering from acne versus those with healthy skin.

They identified two unique strains of P. acnes found in 20 percent of the participants with pimples, that were close to non-existent among those with healthy skin. In addition, another strain of P. acnes was commonly found among the volunteers with healthy skin, yet quite rare in participants with acne.

The researchers believe that this "good" strain has a natural defense mechanism that targets and eliminated attackers that try and infect the cell.

The finding should help in the development of future acne treatments. The researchers believe that by increasing the body's concentrations of the friendly P. acnes strain - through the use of a cream or lotion - acne severity could be reduced.

Li added: "This P. acnes strain may protect the skin, much like yogurt's live bacteria help defend the gut from harmful bugs. Our next step will be to investigate whether a probiotic cream can block bad bacteria from invading the skin and prevent pimples before they start."

Further studies will look into possible drugs that can eliminate the bad strains of the bacteria whilst at the same time preserving the good strains, as well as assessing whether a simple skin test can effectively predict if someone will develop acne in the future.

A previous study, presented at the Society for General Microbiology's Spring Conference in Dublin, revealed that herbal preparations of thyme could well be more effective at treating skin acne than current prescription creams - promising to be a gentler and more effective treatment.

Written by Joseph Nordqvist