1. Presented by Dr. Alisha Ware, MD and reviewed by Karen Carroll, MD and Nikki Parrish, PhD.

A middle-aged patient with a history of a chronic lymphoproliferative disorder presented with ongoing hand pain and stiffness. The pain began following a penetrating hand injuries incurred while working with fish and plant materials. Upon removal of a retained fish fin, the patient experienced intense pain. At that time, the patient presented to the emergency department, where the patient was diagnosed with hand cellulitis/tendinitis. Bacterial cultures at that time grew viridans group Streptococcus, and the patient was discharged on antibiotic therapy with doxycycline and amoxicillin.

Several months later, the patient again presented to the emergency department with persistent hand swelling and pain. Imaging at that time showed persistent flexor tendinitis and soft tissue edema (Figure 1), and the patient was treated with doxycycline and IV vancomycin. Despite a prolonged course of antibiotics, there was little improvement in the patient's symptoms. Due to the severity and persistence of the patient's symptoms, the patient underwent surgical debridement and exploration. Intraoperatively, debridement of marked poorly viable tissue surrounding the flexor tendons was performed, and numerous tissue samples were sent for bacterial, fungal, and mycobacterial cultures at 30o, 37o, and 40oC. On day 10, growth was noted on the bacterial culture at 30oC, and in subsequent days, growth was noted on several of the mycobacterial cultures (Figure 2). A Ziehl-Neelsen stain was performed on one of the colonies (Figure 3).

Figure 1 - MRI showing extensive flexor tendonitis and soft tissue enema of the hand (arrows).




Figure 2 - Growth on a Middlebrook agar plate (Top) and a Lowenstein-Jensen agar slant (Bottom) used for recovery of mycobacteria.




Figure 3 - Ziehl-Neelson stain performed on one of the colonies.


Question
What is the most likely causative organism in this case?