Isolated Pulmonary Valve Infective Endocarditis With Persistent Staphylococcus aureus Bacteremia and Rapid Clearance With Ertapenem Plus Cefazolin.

Infective endocarditis is an infection of the heart's native or prosthetic valves, often caused by bacteria such as Staphylococcus aureus. Although infective endocarditis most commonly affects the left heart, cases of right-sided infective endocarditis, involving structures like the tricuspid or pulmonary valves, are also noted. Isolated native pulmonary valve infective endocarditis is exceptionally rare. After suspicion, the diagnosis relies on clinical symptoms and signs, imaging, and microbiological evidence. We report an unusual case of isolated pulmonary valve infective endocarditis in a previously healthy 59-year-old man without typical risk factors. He presented with unspecific symptoms such as fever, chills, dizziness, and left shoulder pain. Radiologically, the patient presented small ground-glass opacities in both lungs that aggravated during the first days after hospital admission with multifocal consolidation areas, and later developing bilateral necrotizing pneumonia. Despite adequate antibiotic treatment, the patient developed septic shock and persistent Staphylococcus aureus bacteremia. Given the persistence of such microorganisms in the bloodstream, despite the initial absence of endocardial involvement on transthoracic echocardiography, transesophageal echocardiography was done and revealed a large vegetation on the pulmonary valve with valvular regurgitation. According to Duke's criteria for infective endocarditis, a definite diagnosis was made, once both major clinical criteria were present, namely, typical microorganisms consistent with infective endocarditis from two separate blood cultures and evidence of endocardial involvement. Given the refractory bacteremia, an unusual combination of antibiotic therapy, including ertapenem and cefazolin, was introduced, leading to rapid clearance of bacteremia. This salvage antibiotic regimen was chosen due to the synergy of carbapenem with cefazolin and their potential improved bactericidal activity within biofilms. The patient subsequently required surgical intervention with bioprosthetic pulmonary valve replacement and ultimately achieved near-full recovery after a prolonged hospital stay. This case illustrates the diagnostic and therapeutic challenges of rare right-sided infective endocarditis since the patient presented with non-specific symptoms, without typical risk factors for right-sided infective endocarditis and the initial transthoracic echocardiography showed no valvular vegetations. Furthermore, the persistence of bacteremia despite adequate antibiotic therapy was a clinical challenge and this case highlights the potential efficacy of ertapenem plus cefazolin in treating persistent Staphylococcus aureus infections. It underscores the importance of individualized management in severe cases and the need for ongoing research to optimize treatment strategies for persistent infections.