Concurrent pseudogout and septic arthritis in native knee joint by ESBL-producing E. coli: Successful management with cefmetazole and surgery

Septic arthritis in native joints due to extended-spectrum beta-lactamase (ESBL)-producing bacteria is rare, and there is limited information in the current literature. An 85-year-old woman with rheumatoid arthritis experienced persistent left knee pain and mobility issues for several days. Initially, the patient was diagnosed with pseudogout by calcium pyrophosphate deposition and leukocytes in the aspiration fluid. However, joint puncture fluid culture on admission revealed the presence of ESBL-producing <i>Escherichia coli</i>, whereas magnetic resonance imaging showed effusion in the left knee joint and abnormal signal changes in the surrounding soft tissue. Cefmetazole was administered and the patient underwent orthopedic surgery involving arthritis scraping, debridement, and drainage. Post-intervention, she experienced alleviation of knee pain, leading to transfer to a rehabilitation facility on the 35th day of hospitalization. This case highlights an unusual septic arthritis case caused by ESBL-producing bacteria in a nonprosthetic pseudogout-affected joint, underscoring cefmetazole's therapeutic potential.