Persistent Bacteremia Is Rare in Non-Staphylococcal Infective Endocarditis

Persistent bacteremia after a 48-hour course of antibiotic therapy is uncommon among patients with non-staphylococcal infective endocarditis (IE), according to findings published in the International Journal of Cardiology.

Researchers in conducted a retrospective analysis among adult patients hospitalized with confirmed non-staphylococcal IE. Follow-up blood cultures were obtained from all patients during the 90-day study period, with the index culture defined as the first culture that grew clinically significant bacteremia. The primary outcome was the prevalence of persistent bacteremia, defined as any blood culture that grew the same pathogen as that of the index culture after antibiotic therapy for 48 hours or more. Secondary outcomes included 90-mortality and the predictive value of persistent bacteremia in regard to mortality risk. The researchers used multiple logistic regression to determine prognostic value of persistent bacteremia, controlling for native or prosthetic valve type, infectious pathogen, and patient age.

Among a total of 159 patients included in the analysis, the median age was 67 (IQR, 59-74) years, 80% were men, 15% had coronary heart disease, 46% had heart failure, and 20% had diabetes. In addition, 70 (44%) patients had prosthetic valve and 89 (56%) had native valve endocarditis.

For all patients, a median of 2 follow-up blood cultures were obtained within the first week of antibiotic therapy initiation, with at least 1 follow-up culture obtained within the first 4 days in the majority (84%) of patients. Within 48 hours of antibiotic therapy initiation, 7 (4.4%) patients tested positive for persistent bacteremia, of whom 5 had prosthetic valve and 2 had native valve endocarditis.

Of the 7 patients with persistent bacteremia, 5 had IE caused by Enterococcus faecalis,  2 had IE caused by Gram-negative Pseudomonas aeruginosa and Enterobacter cloacae, and 3 underwent valve replacement procedures. The causative pathogen was E faecalis among all 3 patients who required valve replacements.

None of the patients (n=97) with streptococcal infections demonstrated persistent bacteremia.

At 90 days, the rate of mortality and relapse was 15% and 4%, respectively.

Study limitations include the retrospective design, the lack of standardization for blood culture collection, and the possibility that some patients with persistent bacteremia were not recorded due to lack of testing within the first week of antibiotic therapy initiation. 

“Our study challenges the dogma that follow-up blood cultures are necessary in all patients with non-staphylococcal infective endocarditis,” the researchers noted.