Radiometric diagnosis of mycobacteria

The aim of this study was to determine the impact of recently developed rapid radiometric techniques on the clinical diagnostic operations of a reference laboratory for mycobacteria. Selective inhibition by rho-nitro-alpha-acetylamino-beta-hydroxypropiophenone was used to rapidly screen submitted cultures for identification of mycobacterial species other than Mycobacterium tuberculosis. The radiometric drug susceptibility test was applied only to those cultures presumptively identified as belonging to the Mycobacterium tuberculosis complex. All referred cultures were tested without additional subculture. The results showed that non-pigmented mycobacteria other than Mycobacterium tuberculosis can be screened with about 99% reliability, most of them within 24 hours. Unnecessary drug susceptibility testing of mycobacteria other than tubercle bacilli can be avoided at an early stage, thus shortening the average reporting time of the Mycobacterium tuberculosis complex to nine days following the receipt of the cultures. Ways of limiting erroneous reporting are discussed.