This study illustrates a discrepancy between BSI pathogen prevalence and their IE risk, emphasising the need for sufficient granularity in defining species typically linked to IE, and demonstrates a mismatch between echocardiographic screening efforts and the actual IE risk associated with different bloodstream infection pathogens.
Key Findings
Results
The overall prevalence of definite infective endocarditis among bloodstream infections was 2.7% in this single-centre registry.
Registry included 4939 BSIs related to 4242 admissions in 3708 patients from January 2015 to December 2021.
133 cases of definite IE were identified from the total BSI cohort.
Single-centre retrospective registry design covering 7 years of consecutive hospitalised patients.
IE diagnosis followed established diagnostic criteria including Duke criteria and 2023 Duke-ISCVID criteria.
Results
Enterobacterales and Staphylococcus aureus were the most prevalent BSI pathogens, but less frequent organisms carried the highest IE proportions.
Enterobacterales were the most common BSI pathogens at 48.3% of all BSIs.
S. aureus accounted for 11.5% of all BSIs.
Streptococcus bovis complex showed an IE proportion of 19.2% despite being less frequently encountered.
Listeria monocytogenes had an IE proportion of 16.7%, also among the less frequent BSI pathogens.
Results
BSI in patients with intracardiac prosthetic material showed an IE prevalence almost five times higher than the overall BSI population.
The presence of intracardiac prosthetic material was identified as a major predictor of IE in BSI patients.
IE prevalence in this subgroup was approximately five times the 2.7% overall BSI IE prevalence.
This finding underscores the importance of considering host risk factors, not just causative microorganism, when assessing IE risk.
The result highlights that IE risk factors such as prosthetic material should be integrated into screening decisions.
Results
Grouping microorganisms as suggested by major guidelines underestimated IE risk for certain pathogens.
IE risk was underestimated when micro-organisms were grouped as suggested by both ESC and 2023 Duke-ISCVID guidelines.
The study found that insufficient granularity in species classification within guideline-defined 'typical species' categories masked high-risk organisms.
Both European Society of Cardiology and Duke-ISCVID typical species groupings were assessed and found to obscure species-level IE risk differences.
The authors conclude that 'typical microorganism concepts may underestimate high risk if species are grouped or if IE risk factors are ignored.'
Results
Echocardiographic screening rates were highest for S. aureus and Staphylococcus lugdunensis BSIs, but screening rates were inconsistent with actual IE risk across pathogens.
Echocardiography screening was performed in 75% of S. aureus BSI cases.
Staphylococcus lugdunensis BSI had an echocardiography screening rate of 72.2%.
Among BSI without any IE cases identified, echocardiography screening rates still ranged between 27.3% and 59.4%.
The study identifies 'a mismatch between efforts to diagnose definite IE via echocardiography for each microorganism and the IE risk associated with BSI.'
Results
Streptococcus bovis complex and Listeria monocytogenes carried disproportionately high IE risk relative to their BSI prevalence.
Streptococcus bovis complex had an IE proportion of 19.2%, making it one of the highest-risk BSI pathogens for IE.
Listeria monocytogenes had an IE proportion of 16.7% despite being an infrequent cause of BSI.
These findings suggest that rare BSI pathogens should not be overlooked in IE risk stratification due to their high proportional IE rates.
The discrepancy between prevalence and IE risk illustrates why BSI epidemiology data alone does not adequately guide screening priorities.
What This Means
This research suggests that the bacteria causing bloodstream infections (BSIs) — where bacteria enter the bloodstream — vary widely in how likely they are to cause infective endocarditis (IE), a serious infection of the heart valves. Using 7 years of data from over 4,900 bloodstream infection episodes, the study found that the most common bacteria causing BSIs (gut bacteria called Enterobacterales and Staphylococcus aureus) are not necessarily the ones most likely to lead to heart valve infections. Less frequently encountered bacteria such as Streptococcus bovis complex and Listeria monocytogenes were found to cause heart infections in a much higher proportion of their BSI cases — around 1 in 5 or 1 in 6 cases, respectively. Additionally, patients who had artificial heart valves or other implanted heart devices were nearly five times more likely to develop IE from a bloodstream infection compared to the general BSI population.
The study also found that current medical guidelines, which group certain bacteria together as 'typical' causes of IE, may cause clinicians to underestimate the risk for specific species within those groups. When bacteria are lumped into broader categories rather than assessed individually, high-risk species can be overlooked. Furthermore, the study found a mismatch in how often heart ultrasound (echocardiography) was used to screen for IE: screening was most common for S. aureus and Staphylococcus lugdunensis, but for many other pathogens with meaningful IE risk, screening rates were inconsistent with the actual danger they posed.
This research suggests that IE risk assessment should be more individualized — taking into account the specific bacterial species involved and patient-specific factors like the presence of artificial heart implants — rather than relying on broad groupings recommended by guidelines. Improving the precision of both risk stratification and echocardiographic screening decisions could help ensure that high-risk patients receive timely diagnostic evaluation while avoiding unnecessary testing in lower-risk cases.
De Oliveira E, Van Vaerenbergh K, Shumkova M, Beles M, Iturriagagoitia A, Moya A, et al.. (2026). Epidemiology of bloodstream infections and infective endocarditis: new insights on typical species and echocardiography screening.. Open heart. https://doi.org/10.1136/openhrt-2026-004301