Table 3.

Comparison of Methods.

Method	Relevancy	Limitation
Extraction	Optical density of cell suspension linearly predicts the CFU. Count both live and dead cells.	Complete detachment of bacteria is not assured, especially for porous substrates.
Colorimetric	Cell detachment procedure is not necessary. Visualization of bacterial presence is possible, even in the naked eye. Count only the live cells.	Window for accurate quantification is narrow. Observation by the naked eye is difficult at the low level of bacterial concentration.
Microscopy	Direct observation on bacterial distribution on surfaces is possible. Only the topmost surface is observable.	Quantification is not accurate. Observation in depth layer is not possible.