Detection of bacterial DNA in peripheral blood mononuclear cells of patients with reactive arthritis.

Reactive arthritis (ReA) is an infection-induced systemic illness characterized by an aseptic inflammatory joint involvement and occurring in genetically predisposed patients with a bacterial infection localized in a distant organ or system. We evaluated the possible role of bacterial infection in the etiology of reactive arthritis by testing peripheral blood monocytes (PBMCs) for the presence of prokaryotic 16S ribosomal RNA genes which are known as 16S rDNA. PBMCs were isolated from 40 patients with ReA and 10 healthy controls. Clinical, laboratory and radiological evaluations were carried out for all patients and controls. Bacterial DNA was extracted from the PBMCs and subjected to PCR amplification of the 16S rDNA gene followed by DNA sequencing and database comparative analysis. Bacterial DNA was detected in 16/40 (40%) patients and 3/10 (30%) healthy controls. No significant difference was detected between the PCR +ve and -ve groups of patients as regards arthritis, arthralgia, sacroiliitis, low back pain and enthesopathies (P>0.05), while a significant difference was detected in the PCR +ve females with gynaecological infection (P<0.05). A significant difference of the pattern of arthritis was also observed between the two groups of patients. Comparative analysis of 7 16S rDNA sequences from patients and controls using Basic Local Alignment Search Tool (BLAST) and the National Center for Biotechnology Information (NCB1) database revealed high % similarity with potential pathogens and nonpathogenic bacteria. Further studies are needed to establish the exact role of these organisms in the pathogenesis of ReA.