Background
Molecular tests have been proven to be a highly sensible tool to identify the pathogen of infective endocarditis (IE). However, their usefulness in the management of both blood culture positive and valve culture negative IE remains unclear.
Methods
We prospectively enrolled 100 consecutive patients with IE who underwent cardiac surgery between April 2020 and June 2023. Molecular testing (broad-range PCR 16S rRNA) was systematically performed and results were collected together with those of preoperative blood culture, valve culture and histopathological analysis of the specimen.
Results
Blood culture, valve culture and molecular testing were positive in 83%, 47% and 76% of patients, respectively. Both the sensitivity of valve culture and 16S rRNA PCR decreased significantly with increasing duration of preoperative antibiotic therapy. In 7% of cases, molecular test was the only positive test, allowing an etiological diagnosis. In 33% of cases, valve culture was negative but molecular test was positive. In the majority of these patients, histopathological analysis documented acute inflammation. Finally, molecular test clarified discrepancies between the results of blood cultures and those of valve cultures in 12.5% of patients.
Conclusions
The molecular tests showed high sensitivity. Although it decreased as the duration of preoperative antibiotic therapy increased, it was still higher than that of valve culture 28 days after the start of treatment. In addition to patients without an etiological diagnosis, the molecular test proved useful in other circumstances: 1) when the valve culture was negative because, together to the results of the histopathological analysis, it allowed to identify those patients who could benefit from a prolongation of antibiotic treatment; 2) in cases of discordance between the results of blood cultures and those of valve cultures, because it allowed the type of antibiotic treatment to be directed.
Figure 1: Usefulness of molecular tests (PCR) according to the results of blood and valve cultures.
Figure 2: Valve cultures are of paramount importance in the management of antibiotic therapy (ABT). However, their sensibility is low and the risk of under-treatment exists. Molecular tests may help targeting the duration of ABT but they could be persistently positive leading to an over-treatment.
Figure 3: Flow-chart showing the possible role of molecular test in the management of patients with infective endocarditis.
