It is clear that the stroke is one of the most highlight cardiovascular disorders, and traditional risk factors including hypertension, diabetes mellitus, smoking, hyperlipidemia, atrial fibrillation, atherosclerosis, age, male sex, and positive family history can increase the risk of it (13). Predisposing risk factors for emerging and developing of stroke are different regarding differences in individuals, so that increase of stroke in the youth and its trend to autumn and winter shows some interfering modifiable risk factors that are not well known (14). In recent decades understanding of the role of acute and chronic infections in the occurrence of stroke is interested, so that various nested case-control studies have been conducted in this regard. Obviously infection can be lead to inflammation, which in turn triggers some complications such as formation of fatty plaques in the vessel wall, atherogenic reactions, and alteration in host metabolism (15). These changes are as underlying factors for affecting on CVDs especially ischemic stroke (Fig. 2). Of all, the infections caused by pathogens such as C. pneumonia, H. pylori, M. pneumonia, HIV, HSV 1–2, and CMV are more considerable, so that these infectious microorganisms have been frequently isolated from atherosclerosis plaque (16). On the other hand, induction of CIMT and high portion of seropositive population affected by CVD confirm this phenomenon (17). Nowadays there are several documents about the role of bacterial infections in increasing of stroke; for example, infective endocarditis causes to create emboli and arteritis. Moreover, bacterial meningitis and chronic brucellosis can be caused vasculitis and thrombosis in brain arteries, and likewise, rickettsial infections lead to damage of small vascular endothelial cells and the onset of ischemic stroke (14). In recent study the impressive role of bacterial infections in increasing of ischemic stroke was demonstrated, and using statistical analysis of fifty case-control studies we showed that there is a significant relationship between bacterial infection and ischemic stroke cases (OR: 1.7; CI: 1.5–1.8). C. pneumonia is a gram negative and obligate intracellular bacterium that was first introduced in 1980s. More than half of population is infected by this bacterium worldwide, and serological investigations has confirmed this fact (18, 19). In many studies researchers has isolated C. pneumonia from carotid plaques, atherosclerotic plaques, and circulating leukocytes (15). Sander et al. (2004) showed that eradication of C. pneumonia infection can be lead to stop CIMT (20). The clinical trial studies also have shown that the treatment of this infection can be caused reduction of vascular lesions in patients (21). In our study the rate of infection by C. pneumonia in both case and control groups was evaluated 57% and 36% respectively. Also, we showed that there is a meaningful relationship between infection by this bacterium and emergence of ischemic stroke (OR: 2.14; CI: 1.9–2.3). H. pylori is a spiral, gram negative, and microaerophilic bacterium which is colonized in human gastric sub-mucosa about half of the world’s population (22). The rate of infection by this bacterium in developing countries is more than developed countries, so that in some regions of Africa infection by this pathogen reaches about 100% (23, 24). The bacterium is accounted as etiologic agent in disorders such chronic gastritis, peptic ulcer, as well as gastric cancer. However, H. pylori-related extra-gastrointestinal diseases have attracted a lot of attention, in which the relevance of H. pylori infection and CVD is well-known (25, 26). In addition to the several evidence regarding with isolation of H. pylori from atherosclerotic plaques, there are various documents about the effect of infection by this bacterium on some complications including insulin resistance, dyslipidemia, hypertension, and alteration in metabolism which describe the potential role of infection with this bacterium in increasing of ischemic stroke (27, 28). Based on our statistical analysis, the infection by this pathogen in both groups of ischemic stroke patients and age-gender matched healthy individuals was estimated 63% and 55% respectively. We observed a significant relationship between infection by this bacterium and development of ischemic stroke (OR: 1.6; CI: 1.4–1.8). M. pneumonia is one of the respiratory pathogens that in spite of poor understanding about its pathogenicity, many of people have anti-M. pneumonia antibodies (IgG and IgM). In recent several studies have noted to its role in extra-pulmonary manifestations such musculoskeletal, gastrointestinal, dermatologic, hematologic, neurological involvements, and cardiovascular complications (27, 29). According to review of the literature, near the 0.1% of infected to M. pneumonia will get neurological disability during their lives (30). The vasculopathies lesions caused as a result of this bacterial infection are indicating the role of M. pneumonia in increasing the ischemic stroke (14, 31). Two studies in this meta-analysis were related to the role of M. pneumonia in susceptibility to ischemic stroke; infection by this bacterium in both groups of case and control was 55% and 47% respectively. Also, based on statistical analysis we observed no significant relationship between infection by M. pneumonia and ischemic stroke (OR: 0.97; CI: 0.12–7.6). However, the low sample number could effect on outcomes, since only two studies allocated to this bacterium. In addition, high heterogeneity causes instability of results and we need furthermore studies in this regard. M. tuberculosis is one of the threatening pathogens of human life. Although this bacterium usually is known with the term “pulmonary tuberculosis”, but it is a facultative intracellular pathogen which also has extra-pulmonary manifestations (32). In recent years the role of bacterium in promoting of neurological manifestation has been evaluated, so that in result of arterial invasion, malignant vasculitis can be occurred during the tubercular meningitis (14).