Case of the Month - August 2022 A 79-year-old woman presented to the emergency department with localized rash to right knee for three weeks that began after gardening. She had some itching, warmth, and tenderness at the site of the rash. She never had a rash like this previously. She did not have fever, nausea, vomiting, or diarrhea. Her vital signs were BP 175/76, pulse 91, respirations 20, and temp 98.5°F orally. The remainder of her physical exam was notable only for a rash over her right knee (see Figure 1). There was no induration; fluctuance, or broken skin. The knee had full range of motion, and there was no palpable knee joint effusion. Routine blood counts and chemistries were all normal. X-rays of the knee showed soft tissue prominence anterior to the patella, suggesting prepatellar edema and a fluid collection. Lyme antibody screening was negative. Two sets of blood culture bottles were sent to the Microbiology Laboratory for cultures. After 24 hours of incubation, the aerobic bottles of both blood cultures were growing the organism shown in the Gram stain (Figure 2), with growth on blood agar yielding alpha-hemolytic colonies (Figure 3), and H2S production (Figure 4). What is the organism? Figure 1. Rash - right knee. Figure 2 - Gram stain from an aerobic blood culture. Figure 3 - Light growth on blood agar, showing alpha hemolysis. Figure 4 - Positive H2S reaction.