Retractile Mycobacteria in Romanowsky-Stained Bone Marrow Smears: A Comparison of Acid-Fast-Stained Tissue Sections and Romanowsky-Stained Smears

The appearance of mycobacteria was studied in Wright-stained bone marrow preparations of human immunodeficiency virus-infected patients and compared with acid-fast-stained trephine biopsy sections and culture results. Mycobacterium avium complex in Romanowsky-stained preparations may be seen as extracellular and intracellular clear or red refractile beaded rods and nonrefractile "negative images." Refractile mycobacteria were seen in 17 of 20 culture-positive cases. Acid-fast stain of the trephine biopsy demonstrated organisms in only 11 of the 20 cases. Thus, six cases were culture positive and contained refractile rods but had no acid-fast organisms on the trephine biopsy. No false-positive results were seen with Romanowsky stain; the three false-negative results for refractility also were negative with acid-fast stain. Examination of Romanowsky-stained smears or imprints for refractile mycobacteria provides a reliable and sensitive method to identify mycobacteria in this population. Romanowsky-stained bone marrow aspirate and imprint smears should be examined for refractile bacilli when mycobacterial infection is suspected.