Glencorse soil was inoculated with a range of stationary
phase E. coli O157:H7 cell numbers and sampled at various
time points for 35 d. Data indicated survival was dependent
on initial cfu numbers added to soil (Table 3). With lower
numbers of E. coli O157:H7 added, positive PCR amplicons
indicated poorer survival than for soil receiving higher
loadings of target bacteria. Data suggested a 10-fold decrease
in cell concentration each week irrespective of initial cell
concentration. With soil seeded with 3 ´ 105 cfu g±1 soil,
positive PCR signals were observed throughout the 35 d
incubation. However, for soil seeded with only 3 cfu g±1
soil, a positive PCR signal was only observed at 0 d. These
data suggest that a critical loading of E. coli O157:H7 is an
important consideration relating to survival of this microorganism
in soil. The limited studies which have reported
long-term survival of E. coli O157:H7 in soil have used
relatively large inocula of this bacterium (106
±107 cfu g±1 soil)