Complex pathogens in infective endocarditis

Infective endocarditis (IE) is a complex disease whose prognosis depends on the causative microorganism, among other factors. The latter can be difficult to identify and/or treat. In this narrative review, we identify knowledge gaps in the diagnosis and antimicrobial treatment of IE, and attempt to shed light on current questions. Specifically, we: (1) analyze the factors that may hinder the microbiological diagnosis of blood culture-negative IE, as well as the role of new imaging techniques, such as 18F-fluorodeoxyglucose ([18F]FDG PET/CT), in the diagnostic capacity of this disease, understanding their advantages and assuming their limitations; (2) discuss the therapeutic approach to various difficult-to-treat microorganisms. In particular, we focus on the treatment of staphylococcal IE since, at present, staphylococci are the most frequent cause of IE in developed countries and staphylococcal IE is one of those with the highest short- and long-term mortality. We critically evaluate the current evidence on combination therapy and address the occurrence of serious side effects, an aspect that is often overlooked owing to the severity of the infection; and (3) emphasize the need for home antimicrobial treatment of patients with IE, as these are fragile people who benefit from an early return to their environment. This poses undoubted logistical challenges and requires robust evidence to ensure the best short- and long-term outcomes.