1. Presented by Dr. Nicolas Giraldo-Castillo and reviewed by Dr. Karen Carroll.

Clinical Vignette

An adult patient with no significant past medical history developed pain and erythema on their ankle and shin several months after an orthopedic surgical procedure. The patient denied fever, blisters, or drainage. Upon admission, vital signs were T 38.5 C, HR 85/min, BP 120/71 mmHg, RR 16/min and the physical examination was normal except for edema and erythema on the ankle up to the proximal third of shin. Llabs were remarkable for a WBC of 12,670; 87% neutrophils; ESR: 53; and CRP 8.5. A CT scan of the lower extremity showed no drainable collection. Blood cultures were taken and the patient was discharged on oral clindamycin. They returned 4 days later due to an increase in swelling and pain of the left foot.

After four days of incubation, the blood culture aerobic resin bottles showed the following:



This organism only grew on anaerobic CDC plate at 37°C after 72 h. The matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) failed to identify the organism, thus it was sent for 16SrRNA gene sequencing.

Question: What is the most likely microorganism isolated: