On 2014 Jan 24, Gerhard Nebe-von-Caron commented:

Ethidium bromide labels viable and dead cell unless excluded by pumps, as well as carboxyfluorescein negative cells can give rise to colony forming units. The use of CCFDA is recommended to avoid loss of signal due to low intracellular pH.

For an better understanding of viabilty in the context of fluorescent probes please refer to

http://bitc2-preview.sr.unh.edu/TRC/REFERENCES/FC/NebevonCaron2000.pdf

figure 3 for a conceptual understanding of viablity

and figure 6 for the demonstration of uptake of ethidium bromide by live dental plaque. Pumps can exclude both, EB and CFDA.

On 2014 Jan 24, Gerhard Nebe-von-Caron commented:

Ethidium bromide labels viable and dead cell unless excluded by pumps, as well as carboxyfluorescein negative cells can give rise to colony forming units. The use of CCFDA is recommended to avoid loss of signal due to low intracellular pH.

For an better understanding of viabilty in the context of fluorescent probes please refer to

http://bitc2-preview.sr.unh.edu/TRC/REFERENCES/FC/NebevonCaron2000.pdf

figure 3 for a conceptual understanding of viablity

and figure 6 for the demonstration of uptake of ethidium bromide by live dental plaque. Pumps can exclude both, EB and CFDA.