[Molecular identification of mycobacteria and detection of antibiotic resistance].
Mycobacteria are responsible for many human infections, especially species of tuberculosis complex, causative agents of tuberculosis. With nine millions new cases every year, this disease is responsible for more than two millions of deaths. Nontuberculous mycobacteria (e.g. Mycobacterium avium-intracellulare, Mycobacterium kansasii, Mycobacterium xenopi or Mycobacterium ulcerans) can cause infections too, usually in particular clinical settings. Standard diagnosis of mycobacterial infections relies on direct examination and culture. Although culture in liquid media allows the detection of mycobacterial growth at an earlier stage, isolation and phenotypic identification requires several weeks, as does antimicrobial susceptibility testing. Nowadays, molecular tools are available, allowing quicker accurate diagnosis. Detection of Mycobacterium tuberculosis complex by amplification-based tests can be performed directly from clinical samples, although most identifications are successfully after isolation. Several commercial techniques are now available but identification is limited to selected species, at a high cost. Sequencing of genomic targets (such as rrs, rpoB, gyrB, 16S-23S intergenic spacer or hsp65) allows accurate and quick identifications but requires access to a sequencer. Eventually, our better knowledge of the action mechanisms of the different drugs allows genotypic detection of most antibiotic resistances. Indeed, characterization of mutations in specific target genes (such as rpoB, katG, embB, pncA, gyrA or rrl) should be an effective tool for rapid detection of resistance, although this method has only been used so far for rifampin resistance detection. Nevertheless, this approach, limited to reference laboratories, should always be performed in conjunction with antibiogram.
Laboratoire de bactériologie-virologie, Faculté de médecine de Rennes. Vincent.Cattoir@chu-rennes.fr
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D001431:Bacteriological Techniques / Q000379:methods*; D004269:DNA, Bacterial / Q000032:analysis / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005838:Genotype; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods; D008967:Molecular Biology / Q000379:methods*; D009154:Mutation / Q000235:genetics; D009161:Mycobacterium / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D009164:Mycobacterium Infections / Q000382:microbiology*; D021141:Nucleic Acid Amplification Techniques / Q000379:methods*; D010641:Phenotype; D010802:Phylogeny; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013997:Time Factors
D004269:DNA, Bacterial