“…Microorganisms such as Chlamydia trachomatis, Salmonella enteritidis, Shigella flexneri etc have been detected in the joint by immunological techniques and the presence of intra-articular bacterial antigens has now been firmly established with the demonstration of bacteria, bacterial fragments, DNA, RNA, and bacterial lipopolysaccharide in joints of patients with reactive arthritis or sexually acquired reactive arthritis, although there is still some doubt as to the form in which they reach the joint and whether or not they persist (Hughes and Keat, 1994). Some authors in their study concluded that these microorganisms in the inflamed joint might be an important factor in etiopathogenesis of this disease and they are viably active, which supports the hypothesis that arthritis in Reiter's syndrome is probably of the infectious origin (Pavlica et al, 2003;Gerard et al, 1998). However, negative joint culture results from patients with reactive arthritis make it unlikely that bacteria in the joint are viable.…”