1423. A Rare Case of Mycobacterium chelonae Septic Joint

Abstract

Background Nontuberculous mycobacteria (NTM) are ubiquitous environmental organisms that can cause chronic soft tissue infections and which may affect underlying joints and bone by direct extension. NTM septic joint infections are rare and literature on their management is scarce. Methods Here we describe a case of septic ankle due to M. chelonae, a rapid grower NTM, and review treatment of these infections. Results An 86-year-old man presented to our hospital with complaints of a painful left ankle. Three months prior he noticed a pimple on his left foot after tripping over a lawnmower. The lesion evolved into erythema and painful swelling of the left ankle. Magnetic resonance imaging (MRI) of the left lower extremity revealed a fracture of the distal tibial metaphysis. Turbid joint fluid was aspirated showing 211,450 white blood cells with 97% neutrophils. Patient underwent partial removal of the left tibia with insertion of a drug implant device. Culture results showed acid fast bacilli at day three and the pathology report confirmed atypical mycobacterial infection (Fig 1, 2). Empiric meropenem, linezolid, and azithromycin were initiated until the identification of M. chelonae was obtained. Based on susceptibilities meropenem was discontinued and ciprofloxacin was added. A repeat MRI showed osteomyelitis and small abscesses about the left ankle leading to repeat debridement. Cultures from debridement were negative. Tobramycin IV three times a week was added and ciprofloxacin was discontinued. Patient soon developed acute renal failure, NSTEMI, and lactic acidosis. After a goals of care discussion with patient’s family, antibiotics were discontinued. He passed away soon thereafter. The backbone of NTM treatment usually consists of a macrolide plus 2-3 other agents but susceptibilities can be misleading. Data correlating outcomes of in vitro susceptibility and clinical response is mixed. Consequently, management of NTM infections is often derived from case reports and from the tuberculosis literature. As seen in this patient, effective treatment can be elusive. Neutrophils surround vacuoles filled with acid-fast staining organisms on Fite staining H&E Stain shows pink stained organisms in vacuoles Conclusion NTM infections are often resistant to antimycobacterial therapy and require multi-drug regimens with surgical intervention. Due to this complexity, a multidisciplinary approach is vital to improve outcomes. Disclosures All Authors: No reported disclosures.