Streptococcus pneumoniae as a Cause of Mycotic and Infected Aneurysms in Patients without Respiratory Features: Challenging Diagnoses Aided by 16S PCR

Background: Streptococcus pneumoniae is considered a rare cause of mycotic aneurysms. The microbiological diagnosis of mycotic aneurysms can be difficult, and many patients have negative blood culture results. Methods: We describe a series of four consecutive cases of mycotic aneurysms caused by S. pneumoniae with no respiratory features or extravascular septic foci. In two patients with negative blood culture results, 16S PCR was used for the diagnosis of S. pneumoniae infection. Results: Four men with mycotic aneurysms affecting the aorta, axillary, and popliteal arteries caused by S. pneumoniae presented to our center between 2015 and 2016. All were treated with at least one month of intravenous antibiotics, followed by at least 4 weeks of oral antibiotics. Two were additionally managed using endovascular surgical techniques, and one underwent an open surgical repair. The fourth patient presented with bilateral popliteal aneurysms, one of which ruptured and was managed using surgical ligation and bypass, whereas the other side subsequently ruptured and was repaired endovascularly. Three of the four patients are currently off antibiotics and considered cured, while one died of an unrelated cause. Conclusions: S. pneumoniae should be considered a potential causative agent of mycotic aneurysms. Diagnosis can be confirmed using 16S PCR, especially in patients where peripheral blood cultures are uninformative.