Bacterial DNA in Blood Linked to Psoriasis Flare

Janis C. Kelly

March 11, 2015

DNA from bacterial species normally found in the intestinal tract was present in blood samples from some patients with plaque psoriasis during disease flares, researchers report in an article published online March 11 in JAMA Dermatology. The presence of DNA was detected among patients with plaque psoriasis and was associated with higher levels of inflammatory mediators.

Whether the bactDNA, mostly derived from the intestinal lumen, acted as a trigger for psoriasis flares or as a marker for patients likely to develop particularly severe disease was not clear, note Ana Ramírez-Boscá, MD, from the Department of Dermatology, Centro Dermatológico Estético, Alicante, Spain, and colleagues. However, they suggest that the presence of bactDNA does identify a subset of patients likely to have more aggressive disease.

The researchers also suspect that bactDNA, however it gets into the circulation, might trigger disease outbreaks and induce a systemic inflammatory response.

They analyzed peripheral blood samples from 54 consecutive patients with psoriasis who had disease flares after disease that had previously cleared or was controlled with topical medications. They compared patient samples with samples from 27 control subjects matched for sex and age who did not have psoriasis.

The authors found that bactDNA was present in samples from 16 patients, all of whom had plaque psoriasis, but not in six patients with guttate psoriasis, three patients with inverse psoriasis, or 27 control subjects. Twenty-nine patients with plaque psoriasis did not have bactDNA.

Patients with bactDNA were somewhat more likely to have moderate rather than slight disease, to have had a longer time since psoriasis diagnosis (27.5 vs 17.5 years), and to have been younger at diagnosis (15.2 vs 30.2 years).

The patients with psoriasis who were positive for bactDNA also had strikingly higher levels of inflammatory mediators (Table).

Table. Inflammatory Mediators in Psoriasis With vs Without Bacterial DNA in Serum

Inflammatory Mediator (mean pg/mL) BactDNA-Positive Psoriasis (n = 16) BactDNA-Negative Psoriasis (n = 38) P
Interferon γ 130.8 29.7 <.001
Tumor necrosis factor 95.2 21.7 <.001
Interleukin 1β 68.3 13.6 <.001
Interleukin 6 176.8 36.9 <.001
Interleukin 12 125.9 38.8 <.001

Adapted from Ramírez-Boscá et al (2015).

BactDNA sequencing showed that the involved species were Escherichia coli (n = 9), Klebsiella pneumoniae (n = 2), Enterococcus faecalis (n = 2), Proteus mirabilis (n = 1), Streptococcus pyogenes (n = 1), and Shigella fresneli (n = 1). All these organisms are commonly found in the intestinal lumen, which led the researchers to suggest that the increased intestinal permeability associated with psoriasis might have facilitated bacterial translocation and subsequent triggering of a systemic inflammatory response.

The authors have disclosed no relevant financial relationships.

JAMA Dermatol. Published online March 11, 2015. Abstract

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