Microbiological trends in infective endocarditis: a single-centre experience between 2019 and 2023

Infective endocarditis (IE) is a disease associated with high morbidity and mortality. Guidelines recommend specific antibiotic protocols, which must be tailored according to the identified pathogen and its susceptibility profile. The 2023 ESC Guidelines suggest first-line treatments for Streptococcus (Penicillin G, amoxicillin, or ceftriaxone), Staphylococcus (Flucloxacillin or cefazolin), and Enterococcus (Amoxicillin or ampicillin + gentamicin), recommendations that have remained unchanged since the 2015 guidelines. However, a shift in microbiological patterns over time is expected due to increasing patient comorbidities, medical interventions, and antimicrobial usage.

The aim of our study was to analyse the microbiological trends of IE over five years in a single centre, specifically focusing on the prevalent aetiological agents and their resistance profiles, and to assess if the antibiotic regimens suggested in the guidelines align with our local profile.

A retrospective study was conducted, including patients hospitalized with a definitive diagnosis of endocarditis, according to the modified Duke criteria, in the Cardiology department between 2019 and 2023. Clinical, demographic, microbiological, and outcome data were collected.

A total of 84 patients were included, of whom 29 were women (35%). The mean age was 70 ± 12 years (range 23-90 years). There was a median of 20 IE cases per year, with an atypical reduction in cases in 2020 (n=6). The aortic valve was the most frequently affected, followed by the mitral valve. Except for 2021, native valves were most involved. The most frequent causative agent belonged consistently to the Staphylococcus genus. Over the years, the resistance rate to first-line therapy was below 35%; however, a trend towards the emergence of resistance over time was observed. Although first-line therapy resistance has been consistently documented for Staphylococcus, resistance among Streptococcus and Enterococcus species was additionally identified in 2023 (table 1).

Continuous epidemiological surveillance and monitoring of resistance profiles are imperative for the appropriate adjustment of empirical and first-line antibiotic protocols. To robustly confirm emerging trends in antimicrobial resistance, larger-scale, multicentre studies spanning extended periods are warranted. Presently, the therapeutic strategies advocated by existing international guidelines appear adequate for addressing the microbiological profile observed at our institution.