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

## TL;DR

A rare case of infective endocarditis caused by Streptococcus equi subspecies zooepidemicus is reported, highlighting its unusual occurrence in humans.

## Contribution

This paper presents a rare clinical case and literature review of S. zooepidemicus infective endocarditis in humans.

## Key findings

- S. zooepidemicus caused infective endocarditis in a patient with a prosthetic heart valve.
- The infection was complicated by meningitis and myocardial infarction.
- Literature review identified only 13 reported human cases of S. zooepidemicus IE.

## Abstract

Infective endocarditis (IE) is a dreaded disease with a high mortality rate. In Denmark, IE is most often caused by Staphylococcus aureus or Streptococcus 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 Streptococcus equisubspecies zooepidemicus (S. zooepidemicus) 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 S. zooepidemicus was identified in the excised valve tissue. S. zooepidemicus 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 S. zooepidemicus IE in humans.