Rat Bite Fever: It’s Still a Threat

TL;DR

A 32-year-old woman developed septic arthritis from a rat bite, highlighting the rare but serious infection caused by Streptobacillus moniliformis.

Contribution

This case report presents a rare clinical manifestation of rat bite fever through septic arthritis of the PIP joint.

Findings

The patient's infection was confirmed by culture-positive septic arthritis after initial antibiotic treatment failed.

The case highlights the unusual presentation of Streptobacillus moniliformis infection in a PIP joint.

Joint irrigation and debridement were necessary for diagnosis and treatment.

Abstract

Streptobacillus moniliformis is considered normal flora of the upper respiratory tract of rodents and is the predominant cause of rat bite fever in North America. Although patients with rat bite fever oftentimes present with migratory polyarthralgia, cultures of affected joints do not grow bacteria in the vast majority of cases. We present a case of a 32-year-old woman who initially presented with a painful, swollen right index finger proximal interphalangeal (PIP) joint following a bite from her pet rat. After initial treatment with empiric antibiotics did not clear the infection, PIP joint irrigation and debridement revealed culture-positive septic arthritis. This case illustrates the patient’s unusual presentation of S. moniliformis infection through septic arthritis of the PIP joint.

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