Use of culture methods for recovery of atypical mycobacteria from stools of AIDS patients.

OBJECTIVE To establish recovery rates of atypical mycobateria from stools of suspected AIDS patients using culture media. DESIGN Laboratory evaluation of recovery rates, contamination rates, optimum exposure time and optimum concentration of alkali used for decontamination. SETTING The study was conducted in Harare, Zimbabwe at two medical institutions: Beatrice Road Infectious Diseases Hospital (BRIDH) (a tuberculosis referral hospital) and Mashambanzou Care Unit (MCU) (a home-based care centre). SUBJECTS A total of 386 stool specimens from suspected AIDS patients from the two health institutions plus 81 stool specimens from clinically healthy patients were collected. The number of patients from MCU was 144 (49 females, 95 males) and 242 from BRIDH (119 males, 123 females). MAIN OUTCOME MEASURE The main goals were to determine optimum exposure time and optimum concentration of alkali used in decontamination and to identify the culture medium with the best recovery rates of atypical mycobacteria. RESULTS Optimum recovery of atypical mycobacteria was achieved on Peizer TB medium after treating stool specimens with 4% sodium hydroxide for 35 minutes. In addition, the use of Kirchner's medium improved isolation rates, although with a slight increase in contamination at levels of 2.9%. CONCLUSION A stool specimen can be used to recover atypical mycobacteria in suspected AIDS patients. Recovery is achieved using Peizer TB medium at a concentration of 4%. Varying the exposure time of the stool specimen to the decontaminating alkali and incorporating antifungal agents and antibiotics into the medium, improves recovery of atypical mycobacteria.