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Cureus2025; 17(12); e98613; doi: 10.7759/cureus.98613

Streptococcus equi Subspecies zooepidemicus Infective Endocarditis: A Case Report of a Rare Bacterium and Review of the Literature.

Abstract: Infective endocarditis (IE) is a dreaded disease with a high mortality rate. In Denmark, IE is most often caused by or species. We present a rare case of a 50-year-old woman with a history of a dual-chamber pacemaker due to third-degree atrioventricular block and a mechanical mitral valve inserted due to mitral stenosis. The patient was admitted to the hospital after she was found lying on the floor in her home. The patient was diagnosed with subspecies () prosthetic heart valve IE, which was complicated with meningitis, myocardial infarction, and an increasing vegetation load despite antibiotic treatment. The patient underwent heart valve surgery with insertion of a biological mitral valve, and was identified in the excised valve tissue. . is a rare zoonotic pathogen in humans. The bacterium is most often found on the skin and mucous membranes of horses and may cause opportunistic infections in horses and other animals. Our literature review found 11 studies reporting 13 cases with IE in humans.
Copyright © 2025, Jochumsen et al.
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Publication Date: 2025-12-07 PubMed ID: 41503309PubMed Central: PMC12771063DOI: 10.7759/cureus.98613Google Scholar: Lookup
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Summary

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Overview

  • This article reports a rare case of infective endocarditis caused by the bacterium Streptococcus equi subspecies zooepidemicus in a 50-year-old woman with a history of heart valve replacement and pacemaker implantation.
  • The report includes the clinical course, complications, surgical intervention, and a review of the existing literature on this uncommon pathogen causing human infective endocarditis.

Introduction to Infective Endocarditis (IE)

  • IE is a severe infection of the heart’s inner lining or valves, often leading to high mortality.
  • Commonly caused by species such as Staphylococcus or Streptococcus in Denmark and worldwide.
  • Prosthetic heart valves are a known risk factor for developing IE.

Patient Case Description

  • 50-year-old woman with prior heart conditions:
    • Dual-chamber pacemaker implanted due to third-degree atrioventricular block.
    • Mechanical mitral valve replacement because of mitral stenosis.
  • Presented to hospital after being found on the floor at home, suggesting a possible acute clinical event.
  • Diagnosed with prosthetic valve infective endocarditis caused by S. equi subsp. zooepidemicus.

Clinical Complications

  • Patient’s infective endocarditis was complicated by meningitis (infection of the membranes surrounding the brain and spinal cord).
  • Developed myocardial infarction (heart attack), likely secondary to infection or embolism from infected valve vegetation.
  • Despite antibiotic treatment, the vegetation on the valve increased, indicating poor infection control.

Treatment and Outcome

  • Due to complications and progression, the patient underwent heart valve surgery.
  • The mechanical mitral valve was replaced with a biological valve.
  • Analysis of excised valve tissue confirmed the presence of Streptococcus equi subspecies zooepidemicus.

About Streptococcus equi subsp. zooepidemicus

  • Rare zoonotic pathogen, meaning it primarily infects animals but can occasionally infect humans.
  • Commonly found on the skin and mucous membranes of horses.
  • Causes opportunistic infections in horses and sometimes other animals.
  • Human infections are uncommon, but serious when they do occur.

Literature Review Findings

  • The authors reviewed the literature to identify previous cases of IE caused by this bacterium.
  • Found 11 studies reporting a total of 13 patients with infective endocarditis due to S. equi subsp. zooepidemicus.
  • This highlights the extreme rarity of this infection in humans but suggests it can lead to serious cardiac infections.

Significance of the Study

  • Raises awareness among clinicians of this unusual pathogen as a cause of prosthetic valve IE.
  • Emphasizes the need for consideration of zoonotic infections, especially in patients with animal contact or unknown infection sources.
  • Illustrates the challenges in managing complicated IE cases, including the need for both prolonged antibiotics and surgical intervention.
  • Contributes to the sparse literature by adding another documented case and summarizing prior reports.

Cite This Article

APA
Jochumsen S, Kk Vishram-Nielsen J, Pump BB, Seibæk MB, Bruun NE. (2025). Streptococcus equi Subspecies zooepidemicus Infective Endocarditis: A Case Report of a Rare Bacterium and Review of the Literature. Cureus, 17(12), e98613. https://doi.org/10.7759/cureus.98613

Publication

Cureus
ISSN: 2168-8184
NlmUniqueID: 101596737
Country: United States
Language: English
Volume: 17
Issue: 12
Pages: e98613
PII: e98613

Researcher Affiliations

Jochumsen, Sara
  • Department of Cardiology, Zealand University Hospital, Roskilde, DNK.
Kk Vishram-Nielsen, Julie
  • Department of Cardiology, Zealand University Hospital, Roskilde, DNK.
Pump, Bettina B
  • Department of Cardiology, Zealand University Hospital, Roskilde, DNK.
Seibæk, Marie B
  • Department of Cardiology, Zealand University Hospital, Roskilde, DNK.
Bruun, Niels E
  • Department of Cardiology, Zealand University Hospital, Roskilde, DNK.

Conflict of Interest Statement

Human subjects: Informed consent for treatment and open access publication was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.

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Citations

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