TABLE 5.

Detection of R. solanacearum biovar 2 starved and VBNC cells before and after enrichment in MWB in river water microcosms inoculated with this bacterium

Final concn (cells/ml)	Detection resulta
	Before enrichment				After enrichmentb
	Modified SMSA agar	IIF	DASI-ELISA	Co-PCR	Modified SMSA agar	IIF	DASI-ELISA	Co-PCR
Control cells
106	+	+	+	+	+	+	+	+
105-103	+	+	±d	+	+	+	+	+
102-10	+	±d	−	+	+	+	+	+
1-10−2	−	−	−	+	ND	ND	ND	+
Starved cells (25°C)
106	+	+	+	+	+	+	+	+
105-103	+	+	±d	+	+	+	+	+
102-10	+	±d	−	+	+	+	+	+
1-10−2	−	−	−	+	ND	ND	ND	+
VBNC cellsc (4°C)
106	−	+	+	+	+	+	+	+
105-103	−	+	±d	+	±e	+	+	+
102-10	−	±d	−	±f	±e	±e	±e	±f
1-10−2	−	−	−	±f	ND	ND	ND	±f

^aThe detection of stressed cells was done after 10 days to 1 month in the VBNC state. The reported detection limits of IIF, DASI-ELISA, and Co-PCR for R. solanacearum cells are 10³ to 10² cells/ml, 10⁵ cells/ml, and 10⁻² cells/ml, respectively (2, 6, 7, 8).

^bEnrichment was done by the method of Caruso et al. (7) for 72 h at 29 and 35°C. ND, not determined.

^cLess than one culturable R. solanacearum cell per 0.1 ml of solid medium, but 10⁷ cells/ml by total microscopic counts after less than 1 month in the VBNC state.

^dVariable results depending on the number of cells assayed.

^eVariable results depending on the number of cells in the VBNC state, the enriched sampling volumes, and the number of cells enriched in liquid medium.

^fVariable results depending on the DNA integrity of the cells.