"viable numbers" is a correct and usable phrase in written English.
You could use it when referring to numbers or figures that are suitable for a particular purpose, or that have the potential to be effective. For example, "The team examined a range of viable numbers before making a decision."
"As a result of these cuts, courses that are not attracting viable numbers will be forced to close.
To stratify COPD patients presenting with an acute exacerbation on the basis of sputum color and to relate this to the isolation and viable numbers of bacteria recovered on culture.
It is in great hope that many of these captive animals will be encouraged to breed bringing back the population to viable numbers.
Bacterial viability was determined as described above, and the reduction in viable numbers was used to determine the number of bacteria killed.
Also, an incubation with 100µM THPTS followed by illumination, yielded a 6lg (≥99.999%) decrease in the viable numbers of all bacteria strains tested, indicating that the THPTS drug has a high degree of photodynamic inactivation.
By reading and counting the plates after incubation the viable numbers of microorganisms per millilitre was estimated.
There are, for example, some 55,000 Asian elephants -- a viable number for long-term survival -- but they are divided up into hundreds of groups in dozens of different Asian countries, severely reducing their genetic diversity.
Local TV in London is a dead duck and there is precious little sign - despite the hype - that a viable number of people are tuning in to the other English local TV launches in Norwich, Nottingham and Grimsby.
Final CFU was determined by multiplying the dilution factor with the viable number of colonies.
It was necessary to increase the course's catchment area beyond London to attract a viable number of students.
A growth curve was plotted for each cell line depicting the viable number of cells versus the duration post infection.
