Fite stain positivity in Rhodococcus equi: yet another acid-fast organism in respiratory cytology--a case report

Rhodococcus equi is an aerobic Gram-positive and acid-fast coccobacillus that may cause cavitary pneumonia in immunocompromised hosts such as HIV-infected patients. Numerous Grocott's methenamine silver (GMS)-positive organisms were initially noted on the direct smear; a minor number of acid-fast organisms were seen in the Thin-Prep slide. Since the abundant mucous material with the attached organisms seen in conventional smears may be lost in liquid-based preparations, more sensitive stains such as Fite, as well as a more diligent search for organisms, is needed. This case illustrates the importance of careful selection and evaluation of special stains in sputum specimens.