Probe A shown in the GeneXpert MTB/RIF assay during the detection of Mycobacterium intracellular infections

Diagn Microbiol Infect Dis. 2021 Feb;99(2):115243. doi: 10.1016/j.diagmicrobio.2020.115243. Epub 2020 Oct 15.

Abstract

Mycobacterium tuberculosis (MTB) is commonly diagnosed via the GeneXpert MTB/RIF assay. The cycle threshold (Ct) value of probe A from this assay produced a fluorescence signal upon Mycobacterium intracellulare detection. No other nontuberculous mycobacteria (NTM) exhibited positive probe signals. Using a confirmed mycobacterial culture as a standard, probe A of the assay exhibited 84% sensitivity (95% confidence interval [CI]: 71%-97%) and 50% specificity (95% CI: 37%-63%) for clinical samples. For M. intracellulare strains, probe A exhibited 90% sensitivity (95% CI: 80%-100%) and 50% specificity (95% CI: 37%-63%). The identity of the amino acid sequence and 81-bp core region of rpoB from MTB and NTM suggested that the highly conserved property might be associated with a mismatch between the probes and the chromosomal DNA target. Probe A yielded a positive signal upon M. intracellulare detection; thus, probe A may help diagnose M. intracellular infections.

Keywords: Detection; Mycobacterium intracellulare; Xpert MTB/RIF assay.

MeSH terms

  • Bacterial Proteins / genetics
  • Bacteriological Techniques* / standards
  • Drug Resistance, Bacterial / genetics
  • Humans
  • Molecular Diagnostic Techniques*
  • Mycobacterium avium Complex / genetics
  • Mycobacterium avium Complex / isolation & purification*
  • Mycobacterium avium-intracellulare Infection / diagnosis*
  • Mycobacterium tuberculosis / genetics
  • Mycobacterium tuberculosis / isolation & purification
  • Nontuberculous Mycobacteria / genetics
  • Nontuberculous Mycobacteria / isolation & purification
  • Rifampin / pharmacology
  • Sensitivity and Specificity
  • Sequence Analysis

Substances

  • Bacterial Proteins
  • Rifampin