2.3. Growth of beef microflora on selective agar
Experiments were conducted to evaluate the ability of the selective
agar to inhibit the growth of background microflora present in enrichment
cultures from ground beef and beef trim that were not inoculated
with STEC. The ground beef had a 15% fat content and was purchased
from an Ottawa area supermarket, Trim samples were sourced from
an Ontario beef processing plant. Samples of meat 25 g were suspended
in 225 ml of mTSB-VC and incubated for 18–24 h at 42 °C. The postincubation
enrichment broth was then serially diluted at a 1:10 ratio
in PBS (1 ml into 9 ml) from 10−1 to 10−7 and all dilutions manually
spread plated on the eight selective agar and BHI agar. The agar media
were incubated as described above and the total colonies on each
plate enumerated. This experiment was performed with meat from
three separate lots of ground beef and beef trim.