Objective: To make a longitudinal study of antibodies to Klebsiella pneumoniae in patients with ankylosing spondylitis (AS) and to assess treatment effects. As a comparison we measured antibodies of 2 other gut associated bacteria, Escherichia coli and Proteus mirabilis.
Methods: In a double blind study in 84 Finnish outpatients with AS before and after 26 weeks' treatment with sulfasalazine or placebo we measured serum antibodies to Klebsiella pneumoniae, E. coli and Proteus mirabilis with ELISA: Serum samples of 100 healthy blood donors served as controls.
Results: The levels of IgA class antibodies to all 3 bacteria were statistically significantly higher in the sera of the patients compared to the controls. During sulfasalazine treatment significant decreases were observed in concentrations of the IgA class antibodies to Klebsiella and E. coli whereas only a slight decrease was observed in the concentrations of IgA antibodies to Proteus mirabilis. There were no correlations between the clinical and laboratory results observed with sulfasalazine and decrease in concentrations of IgA class antibodies.
Conclusion: Our results agree with the role of gut associated lymphoid tissue in the pathogenesis of AS, but do not totally exclude Klebsiella pneumoniae as a specific agent contributing to the development of AS.