Which microbiological technique is used to quantify viable microorganisms?

The technique used to quantify viable microorganisms is colony-forming unit (CFU) counting. This method involves culturing microorganisms on a solid growth medium and then counting the number of colonies that form. Each colony originates from a single viable microorganism, allowing for an estimation of the number of live cells present in the original sample. CFU counting is a direct measurement of viability, as it only counts those cells capable of growth under the specified conditions.

In contrast, polymerase chain reaction (PCR) primarily detects the genetic material of microorganisms, whether or not they are viable, thereby measuring the presence of DNA rather than live cells. Western blotting is a technique used to detect specific proteins in a sample and is not directly related to quantifying microorganisms. Enzyme-linked immunosorbent assay (ELISA) is used to detect and quantify proteins or antibodies, and while it can provide information about microbial infections, it does not quantify viable microorganisms. Hence, CFU counting is the most appropriate choice for quantifying live microbial populations.