Septic arthritis caused by Granulicatella adiacens: diagnosis by inoculation of synovial fluid into blood culture bottles

Granulicatella species, formerly known as nutritionally variant streptococci, cause a variety of infections, primarily endocarditis. We report the first culture-proven case of a Granulicatella species causing septic arthritis. A 68-year-old female presented with knee pain and swelling. She was initially evaluated with arthrocentesis and arthroscopy, but no organism was identified. Her pain improved after a brief course of antibiotics but recurred 3 months later. She underwent repeat arthrocentesis, with direct inoculation of synovial fluid into blood culture bottles. Granulicatella adiacens was recovered from both bottles. She was treated with cefazolin for 4 weeks combined with gentamicin for the first 2 weeks. Her knee pain and swelling resolved without evidence of recurrence. Granulicatella should be considered in cases of septic arthritis with initially negative synovial fluid cultures. Inoculation of blood cultures bottles with synovial fluid may increase the diagnostic yield for these species.