Aerococcus urinae, a rare cause of aortic root abscess: a case report

Background: Aerococcus urinae is a bacterium of emerging clinical interest that most commonly causes urinary tract infections (UTI) but can also result in invasive infections. It is a catalase-negative, alpha-haemolytic gram-positive coccus that grows in clusters or tetrads and usually causes urinary tract infections. While rare, infective endocarditis must be considered when A. urinae is isolated in blood culture. The mortality rate of A. urinae infective endocarditis is similar to overall endocarditis mortality. We report a rare case of aortic root abscess caused by A. urinae. Case presentation: An 82-year-old Caucasian man presented to hospital with behavioural change and severe malnutrition and was managed for psychotic depression. On day 34 of his inpatient stay, a febrile episode prompted blood cultures, which grew Aerococcus. urinae. Investigations revealed a bicuspid aortic valve, aortic valve endocarditis and aortic root abscess. He also had prostatomegaly. He underwent aortic valve replacement, received 6 weeks of intravenous ceftriaxone and recovered. Conclusion: Infective endocarditis should be considered in patients with persistent Aerococcus urinae bacteraemia. Accurate identification with mass spectrometry is recommended to avoid misidentification as staphylococcus, streptococcus or enterococcus, which is a possibility with conventional laboratory methods.