Digital PCR of spiked sputum samples using rpoBa primers and probes.

aSince the rpoB wild-type probe showed substantial cross reactivity to mutant target (Fig.1B), detection of both wild-type and mutant rpoB probes in a single well was interpreted as presence of mutant sequence if fluorescence signal of mutant probe higher than that of the wild-type probe, and interpreted as a mixed population if fluorescence signal of the mutant probe was equal or lower than that of wild-type probe. Detection of wild-type only rpoB was interpreted as wild-type sequence.bthe dilution that yielded approximately 50% PCR positive.c% mutant = [(n mixed population/2)+n mutant]/total n amplified.