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Failure to identify Salmonella bacteria DNA by polymerase chain reaction in peripheral blood and synovial fluid cells in chinese patients with rheumatoid arthritis and ankylosing spondylitis.

To the Editor: Salmonella infection is a common medical problem all over the world. The clinical syndromes after salmonellosis include fever, vomiting, and diarrhea. Besides enteric symptoms, Salmonella may present other clinical manifestations, such as septic arthritis, osteomyelitis, meningitis, reactive arthritis, conjunctivitis, and erythema nodosum. One percent to 15% of patients with Salmonella gastroenteritis have been shown to develop postinfection reactive arthritis. In Taiwan, Salmonella infection is also a common disease. In 1994, during outbreaks of food-borne disease, 8.1% of cases were caused by Salmonella species. Salmonella can trigger reactive arthritis, and bacterial DNA, including occasional Salmonella DBA, has been found in various arthropathies, including RA. We proposed that PCR could detect Salmonella, either in peripheral blood (PB) or synovial fluids (SF) cells, in patients with RA and AS, which may provide a way of understanding the role of Salmonella infection in these joint diseases. Within a 1-year period, patients enrolled into this study were those in Veterans General Hospital who were diagnosed as having RA (n 24) by ACR criteria and AS (n 13) by New York criteria. All peripheral blood leukocytes from patients with RA, AS and healthy subjects (n 21) were stored at 70°C until use. In patients with arthritis, synovial fluid was obtained via needle aspiration. After hyaluronidase treatment and centrifugation, supernatant and pellet cells were separated and stored at 70°C until use. The Salmonella strain used for the optimization of PCR conditions was S. typhimurium ATCC (American Type Culture Collection) 13311, and ATCC 19585. The primers that we used could detect all the Salmonella species. In this experiment, Salmonella bacteria DNA after amplification by PCR could not be identified in any of the PB or SF samples of either RA or AS patients. In this study, 2 primers of TS5 and TS11 Salmonella-specific 1-step PCR were chosen, and positive as well as negative Salmonella DNA specimens were used as controls. We were unable to find any Salmonella DNA in RA PB and SF cells. All specimens with negative results were reconfirmed by southern hybridization. We spiked on SF with Salmonella and confirmed that our handling of the specimens did not prevent detection by PCR. Our results are consistent with the results of Nikkari et al that Salmonella DNA could not be detected either in ReA or RA peripheral blood leukocytes and SF cells. In Latin America, there is a high prevalence of endemic dysentery, and Salmonella sp. and Shigella are the most prevalent agents, but Cuchacovich et al could not detect Salmonella DNA in either ReA or other patients’ joints. A search of bacterial DNA in 26 RA SF cells using PCR by Australian investigators also failed to detect bacterial DNA in SF. Braun et al examined 104 SF samples of 96 patients with different types of arthritis using nested PCR to detect the presence of bacterial DNA. They also found no Salmonella bacterial DNA in the peripheral joints of patients with ReA, undifferentiated SpA, or RA. Since no Salmonella bacterial DNA can be found in PB and SF cells in patients with RA and AS, an association with a Salmonella infection in RA or AS is unlikely. Detection of bacterial DNA for other infectious agents, including Chlamydia, Parvovirus, Retrovirus, Streptococcus, or even hepatitis B and C, etc. in Chinese patients with reactive arthritis or other inflammatory arthritis is still warranted.