Abdominal Aortic Graft Infection Caused by stG485.0, ST29 Streptococcus dysgalactiae subsp. equisimilis

In recent years, the prevalence of invasive Streptococcus dysgalactiae subsp. equisimilis (SDSE) infections has increased gradually throughout the world, including Japan. Here, we report the case of an abdominal aortic graft infection caused by stG485.0, ST29 SDSE in an elderly patient with diabetes. The patient was an 86-year-old man who had undergone surgery 10 years ago for treating a non-infected abdominal aortic aneurysm using a bifurcated graft. He was referred to our hospital after being suspected of having an abdominal aortic graft infection based on computed tomography (CT) scans. He underwent surgery to drain the pus that had accumulated between the aneurysm and graft. Although blood cultures were negative, the surgical specimen culture was positive for a β-hemolytic group G streptococci, which was subsequently identified as SDSE using 16S ribosomal RNA sequencing. Genetic relationships deduced from emm and multilocus sequence typing revealed the isolate to be types stG485.0 and ST29, respectively. Although aortic aneurysm graft infection has a poor prognosis, we successfully rescued the patient through prompt surgery and identification of the responsible pathogen. This case indicates that attention must be paid toward possible SDSE infections in the field of vascular surgery.