Abstract
Prosthetic joint infections (PJIs) are serious complications of hip and knee arthroplasty. Gram-positive organisms are the most common etiology of PJIs. Less common bacteria and certain fungi may also present as culprits on rare occasions. Listeria monocytogenes and Histoplasma capsulatum are unique etiologies of PJIs. Co-infection with both organisms is even more extraordinary. We present a case of an immunocompromised host with a remote history of right knee arthroplasty who presented with late PJI. Synovial fluid culture revealed Listeria monocytogenes and Histoplasma capsulatum co-infection. Both of these pathogens can form biofilm; therefore, a two-stage exchange surgery is recommended, in addition to antimicrobial treatment. Although these organisms were not expected, with certain epidemiologic risk factors and hosts' conditions, clinicians should always remain vigilant.