Peripheral blood bacterial DNA associated with active psoriasis

Last Updated: 2015-03-19

By Will Boggs MD

NEW YORK (Reuters Health) - Bacterial DNA circulating in the peripheral blood of patients with active psoriasis suggests an association between psoriasis and increased intestinal permeability, researchers from Spain report.

"It remains of great interest to assess if controlling psoriasis may help (block) episodes of bacterial translocation (BT), or if in turn, avoiding BT may help control active plaque psoriasis," Dr. Vicente Navarro-López from Dermatologic Aesthetics Center, Alicante, Spain, told Reuters Health by email. "We can hypothesize that new therapies might help to decrease the levels of systemic inflammatory markers acting as an adjuvant therapy to the currently known treatment for psoriasis and opening the possibility to improve the clinical situation of patients."

Bacterial DNA fragments have been shown to contribute to systemic immunological responses in Crohn's disease and cirrhosis, and intestinal permeability appears to be increased in patients with psoriasis.

Dr. Navarro-López and colleagues measured inflammatory mediators (interferon-gamma, TNF, IL-1beta, IL-6, and IL-12) and looked for the presence of bacterial DNA in the peripheral blood of 54 patients with a flare of psoriasis and 27 sex- and age-matched controls without psoriasis.

Sixteen of the psoriasis patients (29.6%) had blood bacterial DNA, compared with none of 27 controls. These 16 patients all had plaque psoriasis, whereas none of the 6 patients with guttate psoriasis or the 3 with inverse psoriasis had bacterial DNA.

Escherichia coli was the most prevalent source of bacterial DNA (9 of 16 isolates), and the rest of the detected genomic fragments also corresponded to the type of flora commonly found in the intestinal lumen.

The levels of all five inflammatory mediators were significantly higher in patients with bacterial DNA than in patients without bacterial DNA and in controls, according to the March 11 JAMA Dermatology online report.

"Taken together," the authors conclude, "these data suggest a role for bacterial DNA translocation in active plaque psoriasis."

"New studies are needed to clarify if BT is related with the pathogenesis of all phenotypes of psoriasis," Dr. Navarro-López said. "Future investigations on issues such as the intestinal permeability and the intestinal microbiota in psoriatic patients seems necessary to ascertain the real role that all these facts play in the pathogenesis of psoriasis and help designing new therapeutic options."

"We are still in the beginnings of this new finding that is the phenomenon of bacterial translocation in the psoriasis, but multidisciplinary medical treatment involving infectologists, geneticists, immunologists, and dermatologists could be the near future in the treatment of psoriasis," Dr. Navarro-López added.

Dr. Hester Eppinga, from Erasmus MC-University Medical Center Rotterdam, Rotterdam, the Netherlands, has investigated the microbiome in patients with psoriatic arthritis. She told Reuters Health by email, "Indeed, also in other immune-mediated diseases (like inflammatory bowel disease) it is not known if the changes seen in bacterial DNA are cause or effect of the disease. This study found an association, but what this association means remains to be explored. Although there is (mainly in vitro) evidence that bacteria are immunomodulators of the immune system, we cannot conclude from this study that the increased levels of cytokines are caused by the increased presence of bacterial DNA."

"More studies are needed to confirm and explore this observation," Dr. Eppinga said. "Examination of the gut and skin microbiota, together with examination of bacterial translocation to the blood stream, is necessary for a good knowledge of what is going on. When we would know what the consequences of this bacteria in the blood stream are (increased flares of psoriasis, fatigue, infections, other symptoms, or no effect at all), microbiota modulation might or might not gain a place in the future treatment of psoriasis."

"The more you study bacteria in psoriasis, the more you realize we have not got all the answers," Dr. Lionel Fry from Imperial College, London, UK, told Reuters Health by email. "I believe that bacteria are involved in the pathogenesis, but it is too early to say what is their role."

"I do not think the findings in this study will influence the way we treat psoriasis," Dr. Fry said. "The presence of bacteria in the blood may be secondary to what is going in the skin."

The authors did not report any external funding or disclosures.

SOURCE: http://bit.ly/1BTGfwJ

JAMA Dermatol 2015.