SHM Converge Scientific Abstract ePoster Gallery-Saddle Up for a Surprise: Septic Arthritis From an Unusual Source and Etiology

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A 55-year-old man with obesity, gout, prior cervical spine surgeries, and chronic methylprednisolone use presented with right knee septic arthritis after aspiration at an outside hospital. He underwent incision and drainage and was started empirically on vancomycin and cefepime. Blood cultures later grew gram-positive cocci in both bottles, and synovial fluid grew Streptococcus equi, a rare zoonotic pathogen more commonly associated with “strangles” in horses. Susceptibility testing showed ceftriaxone sensitivity, so antibiotics were narrowed to ceftriaxone.<br /><br />Further history suggested indirect animal exposure: the patient lived near a horse farm, and his dog had frequent contact with horses before returning indoors. Workup for bacteremia showed no endocarditis on transesophageal echocardiography, but MRI revealed C5-C7 discitis. Because of his spine history and overall condition, neurosurgery did not recommend operative intervention, and IV antibiotics were continued.<br /><br />He was discharged on six weeks of ceftriaxone, with a planned step-down to oral amoxicillin for three months.<br /><br />This case highlights that Streptococcus equi should be recognized as a true pathogen when isolated from normally sterile sites. Zoonotic transmission can occur through direct or indirect contact with infected animals. Human infections are uncommon but can present as septic arthritis, endocarditis, meningitis, osteomyelitis, or pneumonia. Management depends on prompt antibiotic therapy, source control when needed, and de-escalation based on culture and susceptibility results.

Asset Subtitle

Colin MacKay

Meta Tag

Author List Colin MacKay, Colin Martyn, Harmeet Sohal, Jesse Doyle

Category Clinical Vignettes

Concept Streptococcus equi

Concept Septic Arthritis

Concept Zoonotic Pathogen

Concept Animal exposure

Concept Bacteremia

Distinguished Non-Finalist

Presenter Organization Indiana University School of Medicine Internal Medicine Residency (Southwest)

Presenting Author Colin MacKay

Track Adult

Keywords

Streptococcus equi

septic arthritis

zoonotic infection

gram-positive cocci

ceftriaxone

bacteremia

discitis

horse exposure

synovial fluid culture

antibiotic therapy

Streptococcus equi

Septic Arthritis

Zoonotic Pathogen

Animal exposure

Bacteremia