Clearing the Dust-Off Abiotrophia defectiva

Abiotrophia defectiva (ABI), a nutritional variant Streptococcus (NVS), is an uncommon cause of infective endocarditis (IE) involving both native and prosthetic heart valves. Due to the fastidious nature and special nutritional requirements, contribution of ABI to IE had been underestimated. Here we describe a case of Abiotrophia spp. native valve endocarditis in a 40-year-old female intravenous drug user who did not have any other potential source of infection. Blood cultures grew ABI along with Acinetobacter spp. perhaps from licking the needle before injecting. Transesophageal echocardiogram showed mobile vegetations attached to tricuspid and mitral valves. Susceptibility testing is important due to underlying differences in susceptibility to both penicillin and ceftriaxone between ABI and other genera of NVS, though both antibiotics are recommended alternate empiric first-line therapies along with synergistic gentamicin use in accordance with established guidelines to treat NVS endocarditis. She was successfully treated with intravenous ceftriaxone and gentamicin for 6 weeks with clinical and echocardiographic resolution of IE. This case highlights the importance of modern microbial techniques and equipment for accurate and rapid identification of challenging pathogens.