BACKGROUND AND PURPOSE: Helicobacter pylori and Chlamydia pneumoniae have been 
associated epidemiologically and pathogenetically with coronary atherosclerosis. 
However, population-based data on chronic infection and stroke are lacking. 
Therefore, we investigated the association of both bacterial pathogens and 
ischemic stroke subtypes in a population-based case-control study.
METHODS: Patients with first ischemic stroke in the population-based Erlangen 
Stroke Project were collected as cases. Neighborhood controls were drawn from 
the study population, matched for age, sex, and place of residence. IgG 
antibodies to H pylori were measured by enzyme immunoassay, and IgG antibodies 
to C pneumoniae were measured by microimmunofluorescence technique. Conditional 
logistic regression was used. Analyses were stratified for etiologic stroke 
subtypes according to Trial of Org 10172 in Acute Stroke Treatment (TOAST) 
criteria.
RESULTS: A total of 145 case and 260 control subjects were included. Chronic H 
pylori infection was associated with a higher risk of stroke caused by 
small-artery occlusion (adjusted odds ratio, 3.31; 95% CI, 1.15 to 9.56) and a 
lower risk of cardioembolic stroke (adjusted odds ratio, 0.21; 95% CI, 0.06 to 
0.71). Overall, elevated H pylori as well as elevated C pneumoniae antibodies 
were not associated with ischemic stroke.
CONCLUSIONS: Our population-based study does not provide evidence of any strong 
association between the immune response to C pneumoniae as a marker of prior 
infection and ischemic stroke. Further studies are required to reveal the role 
of chronic H pylori infection as an independent risk factor for the subgroup 
small-artery occlusion.