Four out of five Americans between the ages of 12 and 24 develop acne on their skin, but scientists still struggle to explain its cause. Although clinicians have long assumed that bacteria play an important role, the latest evidence suggests that key genetic differences among the bacterial strains that live in your pores make the difference between picture-perfect skin and unsightly pimples.

A team of scientists from the University of California, Los Angeles, The Genome Institute at Washington University in Saint Louis and the Los Angeles Biomedical Research Institute has conducted the most exhaustive study of acne-associated bacteria yet. As they report in the Journal of Investigative Dermatology (JID) on February 28, the researchers found that some strains may contribute to skin disease whereas others could help fend it off.

“People have been treating acne as though all bacteria were the ‘bad guys’ in acne,” says U.C.L.A. molecular biologist Huiying Li, the study’s principal investigator. “Our study shows that some strains may be bad, but some strains may be good.”

Chances are that playing host to the wrong type of bacteria is not the only cause of the condition formally known as acne vulgaris. Dermatologists have also invoked the role played by hormones, oil glands and clogged pores. Treatments from soaps to prescription antibiotics often target the bacteria in pores. The JID study offers the strongest evidence yet, however, that bacteria play a key role in both causing as well as preventing at least some kinds of acne.

The research team collected samples of bacteria from within the nasal pores by using cleansing strips on 49 acne patients and 52 individuals with healthy skin. They found that a single type of bacteria—Propionibacterium acnes—predominated in the nasal pores of both clear-skinned and acne-prone individuals. To decipher what made the difference, the scientists had to analyze the strains of P. acnes present in pores.

Using select genetic markers, the researchers identified more than 11,000 strains of P. acnes. Further analysis pinpointed the 10 most common strains, dubbed ribotypes 1 through 10. Six of these strains were strongly associated with unhealthy skin. One strain, ribotype 6, was found only on healthy skin. Because these strains exist as part of a community of bacteria, or microbiome, the researchers next profiled the populations that exist within pores. They identified five common microbial combinations and found that two, dominated by ribotypes 4 and 5, were found primarily in acne patients.

These patterns provided more evidence that different strains of P. acnes might relate to healthy or sickly skin. But to investigate whether certain strains could be harming or benefiting human hosts, the researchers needed to study the genetic structure of each.

The scientists sequenced the DNA of 66 isolated samples of P. acnes from 10 different strains and then combined this information with five other published P. acnes genomes. Comparing these 71 genomes, they constructed a family tree that revealed how this species of bacteria had evolved and the genetic variations that had shaped each strain.

At last, the researchers could see why ribotypes 4 and 5 might cause so much trouble. Certain specimens had acquired DNA from other bacteria that could provoke an immune response in the skin or allow bacteria to stick more aggressively to the host. By contrast, the scientists identified a possible explanation for ‘helpful’ bacteria. Select specimens from other strains, such as ribotypes 2 and 6 appear to possess a defense system that could combat invading DNA from harmful viruses. University of California, San Diego, dermatologist Richard Gallo, who was not involved in the study, observes that this finding hints how treatments that wipe out entire bacterial populations may not be appropriate. “Many of us in the scientific community are showing how most bacteria on the skin benefit us,” Gallo says.

5 Comments

1. 1. The Ethical Skeptic 12:32 AM 3/1/13

   Excellent premise in expanding the understanding behind the beneficial bacteria inhabiting our outer microbiome. Confusing results has to make this tough research. Complicating this is the confusion between acne and rosacea infections (inaccurately called adult acne), wherein we find that advice about clear pores and clean skin and topical treatments, simply does not address the malady. By continuing to kneejerk recommend these treatments, we distract both victims and researchers, with good practices certainly, but ultimately ineffective busy work. Doxycycline is effective, but its rather large molecule does not osmosis to the pores, glands and epidermis. It is effective in the blood and small capillaries in the face, forehead and back. So part of this biome pathogen formula resides in the BLOOD. Indeed, in the subdermal capillaries is where rosacea begins its infection. Thus much of what we mistakenly call acne is not acne (in the article definition) - and this can confuse research which does not neutralize this signal through its procedure, covariances or methods.
   
   We need to examine blood born pathogens, and the fermicute phylum in particular, as well and their prospective interplay with both beneficial and unhealthy skin microbes, particularly those passed or who's balance is altered by the intestine flora and blood barrier, and process of bacteria in their contribution to digesting foods.
   
   Right now, Doxycycline is in extraordinarily short supply. As of Feb 28, 2013 it has been prescribed so much for skin infections (many times mistaken for acne) that the retail pharmacy supply chains are 12 - 15% under safety stocks. The FDA levying a $20 fee/tax on the drug per-script in early February has not helped stem the demand. The presumption that all this increase in prescriptions is simply 'unnecessary trends in abuse,' may mask important health data signal. These skin infections are rising at an alarming rate. If we keep calling this acne, keep telling people to wash their faces, and keep looking to confirm 140 year old dogma, we are going to make a mistake. Let's follow the scientific method, be skeptical of old pat answers, introduce new ideas and not immediately cut sponsors off at the knees, in absence of method. When contradictions arise and results are confusing, this is a clue that a foundational assumption is possibly wrong.
   
   But nonetheless, outstanding stuff - go UCSD!!
   
   - TES
   
   

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2. 2. pllackey in reply to The Ethical Skeptic 07:41 AM 3/1/13

   To say that doxycycline is altering a population of blood borne patholgens with a contibution to acne is purely speculation on your part. Doxycyline has additional actions in addition to being an antibiotic. As may be recalled the tertracycline family alters angiogenesis, proteolysis, inflammatory response, and apoptosis in a variety of circumstances removed from bacterial interplay.

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3. 3. science<3 07:13 PM 3/1/13

   We all know that many different strains of bacteria and other microflora and microfauna live on the human body, and that although each person has their own unique set, they are all relatively the same strains, just different ratios of quantities of each.
   These microflora and microfauna can be beneficial, neutral or harmful to the human body, and it all depends on how vastly spread out one colony is compared to the rest, as well as how they interact with the other colonies. Also bear in mind, as stated in the context above, that some may have defensive mechanisms to prevent others from having their colonies grow too big and stealing their food resource and living space. I think dermatologists have been taking the wrong approach in how to combat acne. Instead of using soaps and antibiotics and what have you to try and kill off the majority of bacteria - some of which are good - and then risking the chances of creating resistance in certain strains, we could take a completely different approach, one that I feel will have the best results. Ribotype 6 is found only on healthy skin, and possesses a "beneficial" defensive mechanism, if we encourage the growth of this strain on acne-riddled skin, I feel this would work far better than any other method designed to wipe out entire colonies.
   
   A side note I wish to add that may serve as an excellent excuse for an experiment: It is commonly thought that individuals borne via caesarian lack the microbiota normally inherited through natural birth, and as a result often develop certain problems not normally seen in healthy individuals such as gut problems due to a lack of certain intestinal microbiota. I have a feeling this same rule applies to acne-riddled individuals.

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4. 4. flacoface 07:53 AM 3/2/13

   In response to the Ethical Skeptic
   Bacteria does not exist in the blood of normal, healthy individuals. This includes those with acne. Propionibacteriun acnes is not considered a bloodborne pathogen (think HIV, hepatitis, T. cruzi, and malaria as some examples).
   
   I am not saying that bacteria can't enter the bloodstream. I am saying that the person with P. acnes or any other bacteria circulating in their blood have a much greater medical problem than acne.

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