Aortic Valve Replacement and Penicillin Desensitization in a Patient with Abiotrophia defectiva Aortic Valve Endocarditis

Abiotrophia defectiva is an uncommon and insidious yet destructive cause of infective endocarditis preferentially treated with penicillin/gentamicin and often requiring surgical treatment. A 60-year-old man with penicillin anaphylaxis history presented with fevers and a nonspecific constellation of symptoms. He was ultimately diagnosed with bicuspid aortic valve infective endocarditis based on blood cultures growing A.defectiva and echocardiographic evidence of bicuspid aortic valve, severe valvular regurgitation, and 5 × 7 mm vegetation. Aortic valve replacement and culture yielded penicillin-sensitive A.defectiva. After successful penicillin desensitization, antibiotic therapy was switched from vancomycin/gentamicin to benzylpenicillin. This is the first published case of penicillin desensitization in a patient with A.defectiva-associated infection. Penicillin desensitization, optimal antibiotic therapy, prompt aortic valve replacement, and close collaboration between cardiology and various other specialties were essential in achieving a positive outcome.

Abiotrophia defectiva DnaK Promotes Fibronectin-Mediated Adherence to HUVECs and Induces a Proinflammatory Response

Abiotrophia defectiva is a nutritionally variant streptococci that is found in the oral cavity, and it is an etiologic agent of infective endocarditis. We have previously reported the binding activity of A. defectiva to fibronectin and to human umbilical vein endothelial cells (HUVECs). However, the contribution of some adhesion factors on the binding properties has not been well delineated. In this study, we identified DnaK, a chaperon protein, as being one of the binding molecules of A. defectiva to fibronectin. Recombinant DnaK (rDnaK) bound immobilized fibronectin in a concentration-dependent manner, and anti-DnaK antiserum reduced the binding activity of A. defectiva with both fibronectin and HUVECs. Furthermore, DnaK were observed on the cell surfaces via immune-electroscopic analysis with anti-DnaK antiserum. Expression of IL-8, CCL2, ICAM-1, and VCAM-1 was upregulated with the A. defectiva rDnaK treatment in HUVECs. Furthermore, TNF-α secretion of THP-1 macrophages was also upregulated with the rDnaK. We observed these upregulations in rDnaK treated with polymyxin B, but not in the heat-treated rDnaK. The findings show that A. defectiva DnaK functions not only as an adhesin to HUVECs via the binding to fibronectin but also as a proinflammatory agent in the pathogenicity to cause infective endocarditis.

Frenemies within: An Endocarditis Case in Behçet’s Disease

A 57-year female patient diagnosed with Behçet’s disease, on azathioprine, was noticed to have at a routine examination antinuclear and antiphospholipid antibodies. An overlapping lupus-like syndrome was diagnosed; hydroxychloroquine and aspirin were added. Three years later, the patient presented with dyspnea and sweating, with no fever. A cardiac bruit was noted; a giant vegetation was detected by echocardiography. Laboratory revealed severe thrombocytopenia, antiphospholipid antibodies and low complement. Blood cultures were positive for Abiotrophia defectiva serology and also revealed a chronic Coxiella burnetii infection. Antibiotic therapy, low-dose anticoagulation and control of the underlying disease mildly improved the platelet count, which fully recovered only after cardiac valve replacement. However, the Behçet’s disease, initially quiescent, flared after the therapy of infections. We discuss potential links between Behçet’s disease and the occurrence of antinuclear and antiphospholipid antibodies and Coxiella endocarditis in this setting. We also highlight the differences between the endocarditis in Behçet’s disease, antiphospholipid syndrome, Coxiella burnetii and Abiotrophia defectiva infection, respectively. Intracellular infections may modify the presentation of autoimmune diseases. Confounding clinical features of Coxiella persistent infection and non-bacterial thrombotic endocarditis in Behçet’s disease warrant further insight.

Infective endocarditis by a rare and fastidious agent: Abiotrophia defectiva

Abiotrophia defectiva is a nutritional variant streptococcus, with affinity for endovascular structures that cannot be cultured on non-supplemented media, leading to a delay in diagnosis. This case describes a 36-year-old woman with a previously known bicuspid aortic valve that presented with asthenia, myalgias and anorexia with 2-month onset. On admission, we documented fever and a systolic murmur. Transthoracic echocardiography revealed an oscillating mass attached to the aortic valve. The patient was admitted with a possible diagnosis of infective endocarditis. Later, blood cultures were positive for A. defectiva. Due to severe aortic regurgitation and congestive heart failure, she underwent surgical aortic valve replacement. After 6 weeks of antimicrobial therapy, the patient experienced full recovery. Despite of its rarity, A. defectiva endocarditis is associated with significant morbidity with mortality and physicians must have a high level of suspicion to ensure a prompt diagnosis and provide the appropriate treatment.