Endocarditis caused by methicillin-resistant Staphylococcus aureus (MRSA) is causing about 10.5% of infections in veterans and is associated with a clinically significant increase in mortality among them.
“One factor that is likely contributing to MRSA endocarditis having an increased risk for mortality compared with other pathogens is the virulence factors that this organism contains, including multiple exotoxins and the ability for MRSA to form biofilms,” said Matthew Davis, PharmD, the primary author of a study that looked at this (Open Forum Infect Dis 2025;12[S1]:ofae631.1132). “Also, combining MRSA’s association with a high rate of treatment failure with the need for treatment with prolonged courses of parenteral antibiotics, that are not necessarily well tolerated, may be a large part of why increased mortality was seen in patients who had MRSA endocarditis.”
This retrospective study analyzed national data from veterans diagnosed with endocarditis from 2010 to 2023, and determined that Enterococcus faecalis and Klebsiella pneumoniae also increased the mortality rate. Coupled with other factors, these organisms contributed to the one-year mortality rate of 39.4% observed among infective endocarditis patients.
“The extremely high rate of mortality in this veteran population is surprising despite it being comparable to previous studies in the literature,” said Dr. Davis, a PGY-2 pharmacy resident specializing in infectious diseases at the Western New York Veterans Affairs Healthcare System, in Buffalo, N.Y.
As the authors anticipated, comorbidities including congestive heart failure, cerebrovascular disease, chronic obstructive pulmonary disease, cancer and liver disease increased mortality within one year of infective endocarditis diagnosis. However, certain factors, such as post-infection valve surgical management, were associated with a significant reduction in mortality, which was unexpected, he said.
“An important risk factor for both the acquisition of native valve endocarditis and prognosis following valve replacement is intravenous substance use, especially since the opiate crisis,” said Christopher Longenecker, MD, the director of the Global Cardiovascular Health Program at the University of Washington, in Seattle.
Another surprising result was that patients who used cardioprotective medications–filling at least one prescription before admission and after discharge for infective endocarditis–experienced a significant reduction in mortality. Statins, for instance, decreased mortality rates over a one-year period by 51%.
Dr. Longenecker, who was not affiliated with the study, cautioned against overgeneralizing these findings. “Although statins might theoretically have a beneficial anti-inflammatory effect, it is unlikely that they would lead to 50% lower odds of mortality as seen in this study,” he said. “However, since there are other observational data to suggest statins may reduce endocarditis risk, if someone otherwise has an indication for a statin, this might just be one more reason to take one.”
But there is no randomized trial evidence to suggest statins for everyone at risk for endocarditis, he said.
Additionally, the maintenance use of beta-blockers and sodium-glucose cotransporter-2 inhibitors lowered veteran mortality rates by 60% and 75%, respectively, but the underlying reasons for these outcomes remain unclear, according to Dr. Davis.
Drs. Davis and Longenecker report no relevant financial disclosures.
This article is from the April 2025 print issue.