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Table 2014.07C. Enrichment protocols for the 3M MDA
Listeria monocytogenes
a
Sample matrix
Sample size
Primary enrichment, Demi-Fraser broth (no FAC)
Enrichment broth
volume, mL
Enrichment
temperature
(±1°C)
Enrichment
time, h
Food
Full-fat cottage cheese
25 g
225
37
24-28
Chocolate milk
25 g
225
37
24-28
Beef hot dogs
25 g
225
37
26-30
125 g
1125
37
26-30
Deli turkey
25 g
225
37
26-30
125 g
1125
37
26-30
Cold smoked salmon
25 g
225
37
26-30
Environmental surfaces
Sealed concrete
1 Sponge
100
37
26-30
Sealed concrete, stainless
steel
1 Sponge
225
37
26-30
a
A 24-26 h primary enrichment in Demi-Fraser broth base (no FAC), followed by a 24-26 h
secondary enrichment in Fraser broth base (no FAC), is also acceptable for these matrices.
Candidates for 2016 Method of the Year
145