Les moyens de diagnostic bactériologique de la tuberculose

Microscopic examination of smear after acid fast staining methods has limited sensitivity but is always of prime importance since it permits to diagnose, within 30 minutes, the most contagious cases of tuberculosis. The yield of culture on Lowenstein-Jensen medium for detecting M. tuberculosis is higher than that of direct examination but the delay in obtaining results (3 to 4 weeks) remains a problem. Today, with the Bactec system, the average detection time of in vitro growth of M. tuberculosis among smear negative specimens can be reduced to 14 days and, with DNA probes, cells of complex tuberculosis recovered from culture can be identified within 3 hours. In addition, using genomic analysis it is possible to type M. tuberculosis strains and thus to trace strains in community. At the opposite, the elegant and fascinating method of nucleic acid amplification using polymerase chain reaction, which have given encouraging results in research laboratories, does not permit yet «ultra rapid diagnosis for tuberculosis in clinical laboratories.