Direct Diagnosis of Disseminated Lyme Borreliosis.

Lyme borreliosis is a bacterial multisystemic infection transmitted by an Ixodes tick. It affects the skin, the joint and the brain. At the early phase, the diagnosis is clinical, relying on the presence of an erythema migrans at the site of the tick bite. The diagnosis of disseminated infections, more difficult to assess, mainly relies on indirect diagnosis test, i.e. serology. This study will evaluate a new direct diagnosis method based on proteomics, which aims to demonstrate proteins of live bacteria in the skin and the synovial or cerebrospinal fluids in a direct manner.

Lyme borreliosis is a multisystemic bacterial infection affecting the skin, the joint and the nervous system. It has been shown that the skin is an essential interface as a site of bacteria inoculation and multiplication. In mouse acutely infected with different Borrelia species, the investigators have detected several protein markers of active infection in the skin by discovery proteomics, which allowed us to design a subsequent targeted proteomics assay. The invcestigators tested the same techniques in skin biopsies of humans presenting with an erythema migrans. Most of the bacterial proteins previously identified in the skin of infected mice were also detected in biopsies of human lesional skin. The diagnosis of disseminated Lyme borreliosis currently mainly relies on evocative clinical symptoms along with a positive Borrelia serology. However, a positive serological test does not prove an active infection but merely reflects exposure to the pathogen, which is quite common in endemic regions and thus lacks positive predictive value. Moreover, direct bacteriological diagnosis tools such as culture and nucleic acid amplification (PCR) currently lack sensitivity. Planning to test the ability of proteomics to assist in the diagnosis of disseminated Lyme borreliosis, we have first developed a model of late infection in mouse, and achieved the identification of several bacterial proteins as markers of ongoing infection in the murine skin. The investigators now wish to investigate whether the skin also constitutes a reservoir for these bacteria during persistent disseminated infection in humans, and if they can detect bacterial proteins in this easily accessible tissue by the same approach. They will directly look for bacterial proteins by selected reaction monitoring-mass spectrometry (SRM-MS), the method successfully employed in early infection setting. The ability to detect borrelial proteins in synovial fluid (patients with Lyme arthritis), cerebrospinal fluid (patients with Lyme neuroborreliosis) or lesional skin (patients with acrodermatitis chronica atrophicans) will also be investigated, as appropriated. To improve the detection of Borrelia proteins in healthy-looking skin, a dermocorticoid will be prealably applied for a short 2-days course, a procedure the investigators demonstrated both useful and safe in mice. Since tick bite mainly occurs in the lower part of the body, the upper part of the thigh will be the site of topical steroids application and skin biopsy . The proteomics yield will be compared to the two main other methods of direct detection, i.e. culture and PCR.