TABLE 4.

Comparisons of the Nluc bioluminescence assay for biofilm evaluation with the assays using CFU counting, crystal violet staining, and resazurin fluorescence.

Comparison	Assay
	Nluc	CFU counting	Crystal violet	Resazurin
Mode of detection	Direct	Indirect	Direct	Direct
Biofilm components detected	Live and dead cellsd	Live cells (cultivable)	All biofilm components	Live cells (metabolically active)
Quantification of cells	Absolute	Absolute	Relative	Absolutee
Dynamic rangea	++	++	+	+
Genetic engineering	Required	Not required	Not required	Not required
Time requirementsb	+	++	+	+
Readout instrument	Plate reader	Not required	Plate reader	Plate reader
Sensitivityc	++	++	+	+

^a+, <3 log units; ++, >3 log units. ^b+, <1 h/plate; ++, >1 h/plate. ^c+, <80% of samples here above minimal reliable signal; ++, >80% of samples here above minimal reliable signal. ^dCultivable and non-cultivable cells containing functional Nluc. ^eAbsolute quantification possible (but was not performed here).