SESSION TITLE: Medical Student/Resident Chest Infections Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Mycobacterium (M.) porcinum is a rapidly growing nontuberculous mycobacterium that is genetically related to M. Fortuitum. It has been detected in drinking water and fresh vegetables. In isolation, M. porcinum is considered to be commensal; however, true infections such as cellulitis, peritonitis, catheter-related infection and rarely pneumonitis have been reported secondary to M. Porcinum. We discuss the case of a 69 year old male who was infected with M. Porcinum and tested positive for Quantiferon TB-Gold (QFT). This case report brings to attention that despite the increased reliance on QFT for tuberculosis (TB) diagnosis, it is important to be mindful of its limitations and the possibility of an underlying non-tuberculous mycobacterium infection. CASE PRESENTATION: A 69-year-old male, with a history of COPD and long-term smoking presented with a persistent cough and shortness of breath for the past three months. He was treated for bronchitis without improvement. He denied any fever, chills, rigors or weight loss. CT scan of the chest showed a tree in bud appearance, raising concern for an atypical mycobacterial infection. Sputum for AFB stains were negative along with the Mycobacterium tuberculosis PCR assay. However, the QFT was positive. Further, after two weeks of incubation, AFB cultures were positive for M. Porcinum. The patient was subsequently started on rifampin, clarithromycin and amikacin with symptomatic improvement. DISCUSSION: The QFT gold is an ELISA measuring IFN-γ specific to M. tuberculosis peptides such as ESAT6, CFP-10, and TB7.7. These are present in M. tuberculosis but absent in BCG and other non-tuberculous mycobacterium. Unlike the tuberculin skin test, which measures a delayed hypersensitive reaction to the purified protein derivative present in M. tuberculosis and many atypical mycobacteria, the QFT gold test is an in vitro test that is more specific to M. tuberculosis. However, some tuberculous mycobacterium including M. Fortuitum and M. bovis also harbor ESAT 6, CFP 10, and TB7.7 and can produce falsely-positive QFT gold tests. As demonstrated in our patient, we consider M. porcinum to be a true pathogen. He had concomitant advanced COPD and showed evidence of a tree-in-bud appearance that is typically seen in an atypical Mycobacterium infection. After completing treatment with antibiotics, repeat sputum cultures have been negative. Infections from M. Porcinum have only been reported in a few case reports; however, false positive QFT tests secondary to M. porcinum have yet to be reported in literature. CONCLUSIONS: Although M. porcinum is usually considered commensal, it was regarded as a true pathogen in our patient, as evidenced by the tree in bud appearance on CT, positive M. Porcinum cultures, and a negative Mycobacterium tuberculosis PCR assay. Thus, we consider the QFT in our patient to be falsely-positive. Reference #1: Brown-Elliott BA, Wallace RJ, Tichindelean C, et al. Five-year outbreak of community- and hospital-acquired Mycobacterium porcinum related to public water supplies. J Clin Microbiol 2011;49:4231–8. DISCLOSURES: No relevant relationships by Joseph Leon, source=Web Response No relevant relationships by Mohan Rudrappa, source=Web Response No relevant relationships by Sanket Shah, source=Web Response No relevant relationships by Kunal Shah, source=Web Response