In the last years several new data allow a controversial but convincing interpretation of the pathogenesis of atherosclerosis (arteriosclerosis). Atherosclerosis can be apparently the result of ultrachronic persistent infection by Chlamydia pneumoniae and not the result of different risk factors. The main arguments for the chlamydial genesis are: 1. Correlation of coronary heart disease and other atherosclerotic disease with antibodies against C. pneumoniae. 2. C. pneumoniae could be detected with different techniques (PCR, immunhistology, electromicroscopy, culture) in a high percentage in atheromas from different sites. 3. Three international studies with macrolides in coronary heart disease were successful. 4. The target cells of atherosclerosis (endothelia; macrophages, muscle cells) can be infected by C. pneumoniae in vitro. 5. Positive animal experiments. The Koch-Henle criteria for the proof of the etiology are largely fulfilled - even if there are doubts about the validity of these criteria in chronic local infections. A number of unexplainable aspect of atherosclerosis can be seen in a new light. The higher incidence of coronary heart disease in young males has a parallel in the remarkable androtropism of many bacterial diseases (pneumococcal pneumonia, tuberculosis). The reduction of incidence of atherosclerotic diseases since 1965 can be explained by the much higher intake of doxycyclin and macrolides. The low incidence of coronary heart disease in France - sometimes regarded as an effect of red wine - can be explained as a result of a much higher use of antichlamydial antibiotics. The increase of inflammatory parameters (C-reactive protein,fibrinogen, leucocytes) before acute coronary infarction are not risk factors but signs of an active chronic infection. The interpretation is possible. that atherogenic changes in lipids like increase of LDL and decrease of HDL are not risk factors but consequence of chronic arterial infection by chlamydia. The low incidence of atherosclerosis in the tropics - despite high frequency of chlamydial infection-is difficult to explain Vascular infection can be related with the age of the patient at the primary infection. With low hygiene,intestinal primary infections in early childhood can be possible. Arterial infection would be thus a result of a primary infection in adolescence ("yet another poliomyelitis story"). There are good arguments for the thesis that C. pneumoniae is the primary cause of atherosclerosis and not a secondary invader. The consequence, nevertheless, is similar: Antibiotics get a key role. The macrolides roxithromycin, azithromycin: clarithromycin and the tetracyclin doxycyclin fulfill the criteria as potential antichlamydial agents. In general a longer treatment (6 to 8 to 12 weeks) seems advisable. It is neccessary to start international studies with antibiotics in coronary infarction and other clinical manifestations of atherosclerosis. The relevant antibiotics licensed for chlamydial infections are cheap and safe. Despite of the urgent need for controlled studies, it seems already justified to treat high-risk patients with antibiotics. Meticulous protocols and long-term control of patients are necessary to evaluate the therapeutic effects. Preventive studies in patients without clinical manifestation of atherosclerosis are urgently needed. The risks of resistance or side effects are neglectable. but the organisation of such studies would be very difficult.
