Case Presentation: A 19-year-old female without medical history presented with two days of fever and nausea. Symptoms began abruptly while camping in Canada. She denied tick bites, sick contacts, injections, and trauma other than a cut from a clean razor while shaving. At Urgent Care, she was febrile to 104.9°F, tested negative for influenza and COVID-19, and was treated with ibuprofen and ondansetron. Two days later, she presented to the emergency room with myalgias and dizziness.On presentation, she was afebrile, with a heart rate of 105 bpm and blood pressure of 92/60 mmHg. Initial labs were significant for a platelet count of 53, CRP of 16.1 mg/dL (0.0 – 1.0), and procalcitonin 6.89 ng/mL (< 0.5). CK was 1308 U/L (20 - 21), creatinine 1.14 mg/dl, ALT 102 U/L (10 - 55), and AST 154 U/L (5 - 37). Empiric antibiotics were initiated with piperacillin-tazobactam, vancomycin, and doxycycline. On day two, blood cultures returned positive for methicillin-susceptible staphylococcus aureus (MSSA). Antibiotics were adjusted to Doxycycline 100mg every 12 hours and Oxacillin 2g every 4 hours. Transthoracic echocardiogram (TTE) was unremarkable. Overnight, the patient became disoriented and had visual hallucinations lasting 15 minutes, with symmetrical bilateral upper- and lower-extremity weakness. A physical exam revealed red macular lesions on her palms. MRI of the brain revealed multifocal infarctions concerning for embolic thrombi. CT of the Chest/Abdomen/Pelvis did not reveal an abscess or source of infection. Repeat TTE on day four remained unremarkable, but blood cultures remained positive.A transesophageal echocardiogram (TEE) was aborted due to hypotension. No vegetations were found on the views obtained. Blood cultures remained positive for MSSA despite trials of adjunct Doxycycline and Gentamicin. On day 10, repeat TEE showed thickening of the posterior mitral valve leaflet and a small mass attached beneath the mitral valve. An FDG-PET CT revealed mild avidity in the mitral valve concerning for vegetation. The patient was given a diagnosis of endocarditis. Antibiotics were changed to Oxacillin and Telavancin 7.5 mg/kg daily. Blood cultures returned negative on hospital day 12 and remained so.
Discussion: Although persistently bacteremic, no source of infection was identified on initial testing to enable a diagnosis of endocarditis by the Duke Criteria. FDG-PET CT scan is not typically used to diagnose endocarditis, with a sensitivity of 36% and specificity of 98%. This patient required both repeat TEE and FDG-PET CT to identify the suspected lesion on the mitral valve. However, the patient remained persistently bacteremic despite appropriate therapy.Persistent bacteremia is associated with higher morbidity and mortality rates, with an estimated incidence rate of 6 – 38%. The trial of gentamicin for synergistic effect was unsuccessful. Telavancin is a bactericidal lipoglycopeptide with a dual mechanism of action – including disruption of the cell membrane and inhibition of cell wall synthesis – and dose-dependent bactericidal activity against susceptible gram-positive bacteria. The addition of telavancin to oxacillin led to the resolution of bacteremia.
Conclusions: FDG-PET CT scan is an appropriate imaging modality in cases of suspected endocarditis when cardiac pathology cannot be located by other means. Additionally, telavancin is a viable adjunct to oxacillin in refractory MSSA bacteremia due to endocarditis and should be considered in such cases.