TABLE 1.

Comparison of EMA-PCR with commonly used viable/dead methods^a

Method	Viable/dead criteria	Detection method	Absolute detection limit (log10 cells/g)	Viable/dead differentiation ratio (log10)	Time (h)	Specificity	Analyses of mixed cultures	Flexibleb	Considerations
EMA-PCR	Membrane integrity	PCR	2	4	∼3	Very high	Yes	Yes	Sensitive to high concentrations of material that quench light such as particle contamination
RT-PCR	RNA stability	RT-PCR	3c	Not quantitative	∼5	High	No	No	RNA is very heterogeneous and degradation is dependent on the environment and conditions of the cells
Growth	Ability to divide	Plate counts, limiting dilution, conductance	>1	Does not detect dead cells	>24	Relatively low	Yesd	No	Recovery of viable cells is dependent on the medium used; growth may not be linked to viability
BacLight	Membrane integrity	Fluorescence microscopy and flow cytometry	3	4	∼2	Nonspecific	Noe	No	Low sensitivity and sensitive to particle contamination
CTC	Metabolic activity	Fluorescence microscopy and flow cytometry	5	2	∼5	Nonspecific	No	No	Lack of metabolic activity is not a good indicator of death

^aApproximate values are extracted from references 5, 4, 6, 24, and 29. RT, reverse transcription; CTC, 5-cyano-2,3-ditotyltetrazolium chloride.

^bFlexible means that the approach is easily adaptable to different organisms.

^cBased on our own experience.

^dIf reliable selective media are present for the organisms of interest.

^eCan potentially be adapted to analyses of mixed cultures by combining flow cytometry and cell sorting.