THREE AUTHORS REPLY

摘要

We thank Parratt et al. (1) for their interest in our study (2), in which we found a 50 percent reduction in the risk of multiple sclerosis among penicillin users (at least 3 weeks of use) compared with nonusers during the 3 years before the onset of the disease. Our study findings did not support our original hypothesis that use of antibiotics effective against Chlamydophila pneumoniae was associated with a lower risk of multiple sclerosis. However, this lack of evidence cannot be construed as proof of the absence of an association between chronic infection by C. pneumoniae and multiple sclerosis, as Parratt et al. point out in their letter (1), and as we acknowledge in our paper (2). For example, if the microorganism increases multiple sclerosis risk through chronic stimulation of the immune system, our study design may be unable to find an association, because it is known that short-term treatment for acute respiratory illness (the usual clinical manifestation of C. pneumoniae infection) does not suffice to eliminate this organism in patients with chronic infection (3). Similar arguments have been repeatedly raised to explain the lack of effect of antichlamydial antibiotics in the secondary prevention of cardiovascular outcomes (4)