Neisseria lactamica as a novel cause of prosthetic valve endocarditis in an intravenous drug user: A case report.

Infective endocarditis is a serious complication in people who inject drugs, most caused by Staphylococcus aureus. Gram negative etiologies are rare, and Neisseria lactamica, a commensal of the nasopharynx, has not previously been reported as a cause of infective endocarditis. A 34-year-old man with a history of intravenous drug use, hepatitis C, and recurrent tricuspid valve infective endocarditis presented with petechial rash, fatigue, and dyspnea. Blood cultures grew N. lactamica, and echocardiography revealed new vegetations on a prosthetic tricuspid valve. He was treated with 6 weeks of intravenous ceftriaxone, with resolution of vegetations on follow-up imaging. This is the first reported case of N. lactamica infective endocarditis. Clinicians should consider atypical organisms in people who inject drugs, particularly in prosthetic valve infections. Reporting such cases broadens understanding of rare pathogens and may guide future management.