The effects of enrichment time on detection sensitivity of
the PCR assay were investigated using DNA extracted at
various time points from enrichment cultures of Glencorse
soil spiked with different numbers of E. coli O157:H7. Only
primary enrichment cultures were used in the PCR analysis.
After incubation, under the conditions described previously,
a 15-ml volume of enrichment was centrifuged at 10 000 g
for 15 min to collect cells. DNA extraction and PCR
analysis were as previously described.