Bilateral septic arthritis of the knee caused by group B streptococci: a case report

Septic arthritis (SA) remains to be a critical diagnosis for a swollen knee at the emergency department. Here, we report a rare case of bilateral knee arthritis in a 59-year-old diabetic woman who had been immobilized 5 months prior to admission. Her right knee swelling exacerbated in 10 days leading to left knee involvement. In 5 days the clear synovial tap in the first hospital turned purulent in the second hospital and empirical antibiotics get started with high WBC count, dominant neutrophils, and Gram-positive cocci in smear. Knee arthrotomy was performed after 6 days in the third hospital with the same smear results but negative blood and synovial cultures of both knees. When followed in retrograde, two positive blood cultures were reported for Streptococcus agalactiae in the second hospital. Vancomycin was changed to ampicillin and symptoms were resolved in 4 weeks. Despite improvement, mobility was not retained. Uncommon etiologic agents of knee arthritis should be in mind specifically in debilitated patients. Timely initiation of proper antibiotics hinders permanent sequels, hence clinicians should be suspicious of such organisms.