Comparison of genotypic and phenotypic drug resistance results for respiratory and nonrespiratory specimens

MethodDrug (concn [μg/ml]) or target gene/probeaPhenotypic drug resistance pattern or interpretable genotypic rpoB or katG mutation pattern for no. of samples (n)b
n = 3cn = 4n = 1n = 2n = 1dn = 6n = 3n = 4
Phenotypic DSTRifampin (2.0)RRRRSSSS
Isoniazid (0.1)RRRRRRRR
Isoniazid (0.4)RRRRRRRS
Isoniazid (2.0)RRSSRRSS
rpoB probe assayrpoB WT1++++++++
rpoB WT2+/−++++/−+++
rpoB WT3++++++++
rpoB WT4+++/−++++
rpoB WT5+/−+/−++/−++++
rpoB D516V mutation+
rpoB H526Y mutation++
rpoB H526D mutation
rpoB S531L mutation++
katG probe assaykatG WT++
katG S315T1 mutation+++++
katG S315T2 mutation
  • a WT, wild type.

  • b R, resistant by BACTEC 460; S, sensitive by BACTEC 460; +, band at the respective wild-type or mutant probe zone; +/−, weak band at the respective wild-type or mutant probe zone (for the wild type, a weakened band indicates the presence of a mixed subpopulation of drug-resistant and -sensitive bacteria); −, absent band at the respective wild-type or mutant probe zone.

  • c A clear rpoB S531L mutation and a second D516V mutation (weak band) as strong as the universal control assumed to be a true mutation combined with the absence of the katG wild-type probe, indicating RIF and INH resistance.

  • d A weak wild-type probe band 2 for rpoB indicated at least partial (≤1% of the bacterial population) RIF resistance in combination with an INH S315T1 mutation.