Abstract. Case presentation of a 66 year old female with penicillin hypersensitivity, who suffered late acute periprosthetic infection of her total knee replacement. After emergency surgery and admission to intensive care, the responsible organism was later identified as Streptobacillus moniliformis.This serves as the first documented case of Streptobacillus moniliformis prosthetic joint infection. As standard culture mediums provide an exceedingly low detection rate, 16S PCR should instead be used as the first line method of identification. As a result, its detection is largely dependent on clinicians recognising relevant factors within the patient's history, namely close contact with rodents. In a patient with penicillin hypersensitivity, carbapenems have demonstrated potential as an effective treatment strategy.