title: Mistaken identity: Legionella micdadei appearing as acid-fast bacilli on lung biopsy of a hematopoietic stem cell transplant patient.
abstract: Legionella micdadei is a potential cause of invasive lung infections in immunocompromised hosts. On biopsy specimens, it can appear as an acid-fast bacillus (AFB) and can be mistaken for a member of genus Mycobacterium. As Legionella requires selective media to grow in culture, and the commonly used, commercially available urine antigen test for Legionella only detects Legionella pneumophila serogroup-1, but not L. micdadei, it is important to consider this organism in the differential diagnosis for AFB in immunocompromised hosts. We report a case of L. micdadei infection, which was initially treated empirically for non-tuberculous mycobacteria based on AFB staining of biopsy tissue before the final diagnosis was made.
authors.affiliation: Division of Infectious Diseases and Geographic Medicine, Stanford University, Stanford, California, USA.
authors.forename: P R
authors.initials: PR
authors.lastname: Waldron
authors.forename: B A
authors.initials: BA
authors.lastname: Martin
authors.forename: D Y
authors.initials: DY
authors.lastname: Ho
mesh_terms: D000368:Aged; D000942:Antigens, Bacterial / Q000276:immunology*; D001706:Biopsy; D003937:Diagnosis, Differential; D017809:Fatal Outcome; D018380:Hematopoietic Stem Cell Transplantation; D006801:Humans; D016867:Immunocompromised Host / Q000276:immunology*; D007875:Legionella / Q000276:immunology / Q000302:isolation & purification*; D007876:Legionellosis / Q000175:diagnosis* / Q000382:microbiology / Q000601:surgery; D008171:Lung Diseases / Q000175:diagnosis* / Q000382:microbiology / Q000601:surgery; D008297:Male; D014057:Tomography, X-Ray Computed
chemical_list: D000942:Antigens, Bacterial
keywords: Legionella micdadei; hematopoietic stem cell transplant; legionellosis; pneumonia