Second reported case of human infection with Streptococcus equi subsp. ruminatorum

Abstract

The field of zoonoses changes constantly. Streptococcus equi subsp. ruminatorum is a group C Streptococcus subspecies first identified in 2004. The first case of human infection with this agent was reported in 2007. Here, we report a second case. A 70-year-old man had acute spondylodiscitis and endocarditis involving the anterior mitral valve leaflet. S. equi subsp. ruminatorum was identified in the blood cultures. Antibiotic therapy was successful in eradicating the infection. The workup showed hypogammaglobulinemia with stage I myeloma. He reported frequent contacts with horses including two that exhibited symptoms of upper airway infection a few days before his symptoms started. Serological tests indicated S. equi infection in both animals. This unusual case confirms that S. equi subsp. ruminatorum can cause human disease. In addition, our patient was probably contaminated via the skin, a mode of transmission that has not been described previously. It also highlights the usefulness of molecular biology tests, which should be performed routinely in patients with group C streptococcus infections and evidence suggesting a zoonosis.