Knee Septic Arthritis Caused by Rothia Mucilaginosa and Erysipelothrix Rhusiopathiae

Introduction We found no reported cases in the available literature of knee septic arthritis caused by both R. mucilaginosa and E. rhusiopathiae, which is a rare occupational pathogen affecting animal handlers, while R. mucilaginosa can cause serious infections, especially in immunocompromised hosts. Case Presentation In 2019-05-24, 59 y. o. male patient underwent right knee arthroscopy due to degenerative changes of the meniscus. After two weeks patient started to feel pain. Blood tests revealed leucocytosis, MRI (magnetic resonance imaging) showed proliferative synovitis. 2020-02-03 knee arthrocentesis showed right knee joint inflammation, culture testing revealed E. rhusiopathiae susceptible to penicillin, ciprofloxacin. Antibiotic therapy with ciprofloxacin was started for 2 weeks but signs of inflammation persisted. Arthroscopic synovectomy was performed and cultures revealed two rare bacteria’s: R. mucilaginosa and E. rhusiopathiae. Vancomycin was prescribed. Later, arthroscopic and open synovectomy was performed but clinical signs remained. MRI showed inflammatory changes and necrosis of lateral condyle of femur. X-ray showed III-degree osteoarthrosis. 2023-12-27 trauma caused knee abrasion, likely leading to cellulitis. Knee fluid showed infection. Decision was made to perform 2 stages TKA (total knee arthroplasty). 2024-01-03 I stage TKA performed, and MOLD with vancomycin implanted. Culture revealed staphylococcus aureus and after empirical treatment Biseptol was prescribed, 4 months later there was no more signs of infection and II stage of TKA was accomplished, the patient is still infection-free. Discussion Sources refers that typically E. rhusiopathiae septic arthritis presents as a chronic process involving a single joint, particularly the knee. This pathogen should be suspected if there is a history of animal contact. In both infections C-reactive protein level usually are low. Also, both pathogens can be resistant to some commonly used antibiotics, which can make difficult to treat these rare infections. [1–4]. TKA was necessary due to persistent infection, necrosis, and advanced osteoarthritis. Conclusions The described case highlights the importance of anamnesis, early diagnostics and knowledge about possible rare pathogens multidrug resistance to ensure appropriate treatment of the illness.