[en] A unique case of mycotic aneurysm of the abdominal aorta caused by Streptococcus agalactiae in an afebrile patient presenting with abdominal pain is described. Although this bacterium is associated with a variety of infections in human beings, aortitis is uncommon. Chronic alcoholism and diabetes mellitus are the 2 major predisposing conditions for group B Streptococci infection and both were present in this case. The abdominal pain and elevated inflammatory markers in the absence of fever were elusive in presentation; however, the diagnosis of mycotic aneurysm was established by abdominal computed tomography scan. The patient was treated successfully by resection of the diseased aorta and aortic allograft replacement. Culture of the excised tissue grew Streptococcus agalactiae sensitive to penicillin G and (other commonly tested antibiotics) fluoroquinolones. A prolonged course of moxifloxacin (for 6 months) was administered due to the persistence of elevated inflammatory markers and was remarkably well tolerated. Sixteen months after stopping the antibiotics, the patient is doing well, and the control imaging studies are satisfactory.