(590) A Case of Abiotrophia defectiva Bacteremia Leading to Infective Endocarditis

Introduction: Infective endocarditis (IE) is a serious infection of the endocardium, typically involving heart valves. While Staphylococcus and Streptococcus species are commonly implicated pathogens, less frequently encountered organisms such as A. defectiva can cause IE. A. defectiva is a nutritionally variant streptococcus that poses diagnostic challenges due to its fastidious growth requirements. We present a case of Abiotrophia defectiva bacteremia progressing to infective endocarditis in the ICU setting. We aim to underscore the importance of early recognition, appropriate diagnostic evaluation, and prompt initiation of targeted antimicrobial therapy in managing this potentially life-threatening condition.

Description: 70-year-old female with pertinent past medical history of recently treated UTI and pneumonia who presented to the Medical Center with septic shock and altered mental status. On prior discharge, the patient had a PICC line placed for IV treatment of UTI and pneumonia with meropenem 500mg, linezolid 600mg and fluconazole 400mg. On presentation the patient was intubated due to acute encephalopathy. Culture of the PICC line showed Abiotrophia Defectiva while blood cultures throughout the stay were negative. Patient was started on ceftriaxone 2g. TEE was performed and showed a filamentous mobile echodensity attached to the pacemaker lead likely a vegetation. A plan for pacemaker lead removal was initiated.

Discussion: Abiotrophia species, including A. defectiva, are part of the flora of the human oral cavity and upper respiratory tract. While they are typically low-virulence organisms, they can cause significant infections, particularly in the setting of bacteremia and predisposing factors such as dental procedures or underlying cardiac abnormalities. In this case, the absence of known cardiac risk factors highlights the potential for A. defectiva to cause IE in otherwise healthy individuals. Diagnosis of IE relies on a clinical, microbiological, and echocardiographic findings. Echocardiography plays a crucial role in detecting valvular vegetations and assessing the extent of cardiac involvement. Blood cultures remain the cornerstone for identifying causative pathogens, although special culture techniques may be necessary for detecting fastidious organisms like A. defectiva.