Bacteriology USMLE Step 1 Practice Question

A 55-year-old man with rheumatoid arthritis managed with infliximab presents to clinic with a 3-week history of a painless, indurated ulcer with minimal drainage on his left forearm. He reports a cut sustained while cleaning fish tanks at home 4 weeks prior. Vital signs are stable with a normal body temperature. Physical examination reveals a well-demarcated, violaceous nodule with central ulceration and no regional lymphadenopathy. Culture on standard media at 37°C is negative. Subsequent culture on media incubated at 30°C yields growth of acid-fast positive bacilli. The organism shows optimal growth at temperatures below body temperature and does not grow at 37°C. Which of the following organisms is most likely responsible for this infection?