CFUbased

CFUbased refers to methods and data that rely on colony forming units (CFUs) to quantify viable microorganisms. In microbiology, CFU is used as a proxy for living cells because a colony on a solid medium typically originates from a single viable cell or from a small cluster capable of growth into a colony. CFUbased quantification is common in clinical diagnostics, food safety, environmental monitoring, and biotechnology, and is often expressed as CFU per milliliter (CFU/mL) or CFU per gram.

The typical workflow involves diluting a sample and spreading or pouring aliquots onto appropriate agar plates, followed by incubation under conditions suitable for the target organism. After incubation, colonies are counted, and the CFU count is calculated by multiplying by the dilution factor. The resulting value provides an estimate of the concentration of viable cells in the original sample.

Advantages of CFUbased counting include its relative simplicity, low cost, and the ability to assess viability, as only living cells that can form colonies are detected. It also allows selective enrichment or differentiation using specific media.

Limitations include the assumption that each colony arises from a single viable cell, which can be violated by cell clumping. Some viable cells do not form colonies under the tested conditions, leading to underestimation (the viable but nonculturable state). The method is time-consuming, typically requiring 24 to 72 hours for growth, and results depend on proper dilution, plating, and incubation conditions. Alternatives such as direct counting, flow cytometry, qPCR, or ATP assays can complement CFU-based approaches, each with its own trade-offs.

In practice, CFU/mL remains a widely used, culture-based metric for estimating viable microbial abundance.