Background The incidence of experimental arthritis induced by Yersinia enterocolitica O:8 (YeO8) in animals of different species and strains varies greatly, depending on the the susceptibility of the strain and the dose.1,2 The susceptibility is easily affected by many factors. To increase the incidence of arthritis we used repeated injections of YeO8.
Objectives To evaluate the ability to cause reactive arthritis (ReA) in Lewis rats by repeated i.v. injections of various doses of live YeO8.
Methods 3 experiments were performed on 30 male Lewis rats. Bacterial culture of virulent YeO8 for each experiment were prepared according to usual methods and injected into the tail veins of rats in doses 4 × 10 7 ? 6 × 10 9. The limbs of animals were examined 5 times/week, the severity of joint swelling was assessed by score from 0 to 4. At the end of experiment rats were decapitated and pathomorphological examination of joints and YeO8 detection in the internal organs were performed.
Results In the first experiment 10 male rats were i.v. injected with YeO8 in a dose 4 × 10 7, but no signs of ReA were observed. Injection of YeO8 was repeated two weeks later in a dose 8 × 10 8, but it also showed no joint swelling. Third inoculation (6 × 10 9) of YeO8 induced arthritis in 40% of rats on day 10 after the last injection (swelling scores 1.5–3). Joint swelling decreased to the level of 1 score in 3 weeks. In the 2nd experiment, injection of YeO8 in a dose of 1 × 10 8 induced joint swelling in 20% of rats. Repeared injection of higher dose (3 × 10 8) two weeks later induced ReA in 40% of animals (swelling scores 1.5–4), but 3 weeks after the last injection it was observed only in 20% of rats (swelling score 2). In the 3rd experiment high dose of YeO8 (1 × 10 9) was used and it caused the lethality of 50% of rats. One week after Ye inoculation joint swelling (score 2) developed in 20% of animals. All arthritides were confirmed by histology.
Conclusion The incidence of arthritis varied by using different bacterial doses. Although i.v. injection of YeO8 in lower doses showed no signs of joint swelling, repeated injections were able to cause ReA, but the doses of bacteria were extremely high. The use of high doses of YeO8 for previously non-infected animals, showed high lethality, which didn’t correlate with a high incidence of arthritis.
Gripenberg-Lerche C, Toivanen P. Variability in the induction of the experimental arthritis: Yersinia associated arthritis in Lewis rats. Scand J Rheumatol. 1994;23:124–7
Di Genaro MS, Escudero ME, Muñoz E, et al. Arthritogenicity of Yersinia enterocolitica O:8 in hamsters: analysis of the immune response. Folia Microbiol (Praha) 1998;43(6):690–6
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