A promising cultural-biomolecular method for rapid isolation and identification of mycobacteria

Abstract

Early detection and identification of mycobacteria in clinical specimens is of great importance for the control of infection and timely choice of drug therapy. Although direct detection of mycobacteria by polymerase chain reaction (PCR)-based methods is able to provide information within 24-48 h [1-5], conventional culture remains the most reliable diagnostic tool and permits subsequent identification of the isolated mycobacteria and susceptibility testing. It is therefore important to develop a system or medium for the culture of mycobacteria that is sensitive and provides specific identification by molecular methods in the shortest time possible. A preliminary study evaluating a new nonradiometric cultural method for the detection of mycobacteria has been reported [6]. This test, MB Redox (Biotest, Dreiech, Germany), is a manual colorimetric cultural system which includes a modified serum-supplemented Kirchner medium containing the antibiotic mixture PACT (polymixin B, amphotericin B, carbenicillin and trimethoprim) and specific growth additives. The purpose of this investigation was to evaluate the sensitivity and specificity of a coupled cultural-biomolecular method (MB Redox-multiplex PCR) for rapid isolation of mycobacteria and identification of the genus Mycobacierium, and the individual species M. tuberculosis, M. avium and M. intracellulare. The present study describes initial trial experiments with the method in which multiplex PCR was performed on cultures growing in the MB Redox system. The time taken to obtain a positive result was then compared with the time taken for culture alone. The mycobacterial strains used in this work were: