Case Presentation:
A 59-year-old male with a bicuspid aortic valve presented to the hospital with a syncopal event. One week earlier, a transesophageal echocardiogram (TEE) done for preoperative assessment had confirmed a heavily calcified bicuspid aortic valve and severe aortic insufficiency. He also reported 2 months of night sweats without fevers, 25-pound weight loss, and marked fatigue. Extensive outpatient workup including EGD, Colonoscopy, CT, bone marrow biopsy, tick-borne diseases, viruses, and SPEP were negative. He denied travel history or animal exposure, and reported negative PPD after remote incarceration. On admission he was hypotensive with signs of heart failure and grade II/VI systolic and diastolic murmurs. Labs showed AKI and anemia. Overnight he spiked a fever to 104F and blood cultures were sent. Abdominal CT showed multiple splenic lesions. 4/4 blood cultures returned positive for GPC and GPR and Vancomycin was started. Transthoracic echocardiogram (TTE), initially read as unchanged, showed a 1.5cm echodensity on the aortic valve, consistent with subacute bacterial endocarditis. CT face showed caries, periapical lucencies, and cortical destruction of the mandible and maxilla. Abiotrophia defectiva was speciated from initial cultures. In consult with Infectious Disease, antibiotics were switched to Penicillin G and Gentamicin.
The patient underwent tooth extraction, bovine aortic valve replacement, annulus abscess debridement, and mitral valve repair. Postoperative TTE revealed a persistent aortic root abscess versus surgical pocket, with an aortic root fistula and severe paravalvular insufficiency. Clinically improved, he was discharged on HD 25. After discharge, A. defectiva sensitivities identified Penicillin resistance (MIC ≥ 0.5) so Gentamicin was continued. Antibiotics finished 6 weeks after infected valve tissue had been removed. Subsequent blood cultures were negative. A repeat TTE is planned to help determine whether the persistent aortic root pocket or fistula need intervention.
Discussion:
This case represents a classic presentation of subacute bacterial endocarditis. The false-negative TEE 7 days prior to admission delayed the diagnosis. TEE has a sensitivity of 92%, but can still miss small vegetations. Management was complicated by the rare (incidence 0.75 per 100,000 US population) and aggressive streptococcal variant organism A. defectiva which has high rates of embolism, valvular destruction, antibiotic failure, and mortality. It yields pleomorphic forms by Gram Stain, and culture growth requires extended incubation time and solid media supplementation with pyridoxal or cysteine. Treatment is based on Penicillin MIC data, which took 3.5 weeks to obtain in this case.
Conclusions:
1. If there is a high pre-test probability of infection, a negative TEE should be repeated in 3-5 days, or sooner with a change in clinical status.
2. Abiotrophia defectiva is a rare but prototypical organism that causes infective endocarditis.