930-931 / 1195
20
streaked to MOX if darkening occurred. Presumptive colonies from the FB-streaked MOX were transferred to HL (horse blood
1
overlay agar) for further confirmation and incubated at 35 ±1°C for 22h (confirmation from FB was same as from UVM).
2
3
AOAC reference method
(processed cheese, ice cream)
4
5
Twenty 25 gram portions of the cheese and ice cream were enriched with 225 ml of selective enrichment medium (prepared per
6
method instructions), mixed at high speed for 2 minutes and incubated at 30 ± 1°C for 48 hours. After 48 hours, the selective
7
enrichment was streaked to Oxford agar (OXA) and incubated 37 ± 1°C for 48 hours. Confirmation was according to AOAC 993.12.
8
9
LMX method (detection all foods)
10
11
Pre-enrichment: twenty 25g inoculated samples and five 25g uninoculated samples were added to 225 ml of supplemented LMX
12
Broth. Samples were then stomached for 2 minutes prior to incubation for 26-30 h at 37±1°C. Following incubation, 0.25ml of broth
13
was transferred to sample well of the LMX test strip and heated for 5±1 minutes on the VIDAS Heat& Go. The strip was then
14
removed and left to cool at room temperature for 10 minutes prior to performing the VIDAS assay.
15
16
Confirmation for all methods
17
18
Enriched samples were streaked to Oxford agar (OA) (FDA BAM and AOAC methods) or MOX (USDA method) as well as to
19
Chrom ID Ottaviani Agosti agar (OAA) and ChromID L mono agar for the VIDAS method. Plates were incubated for 24-48h at
20
35°C. The presence or absence of typical colonies was recorded and a minimum of one colony from each of the 3 plating media was
21
streaked to TSAYE (BAM, AOAC) or HL agar (USDA) for confirmation. Typical
L.monocytogenes
colonies were confirmed using
22
the bioMerieux VITEK
®
method, AOAC Official Method 992.19 (10) in the internal study and by Remel MICRO-ID
®
Listeria
23
Microbiological Identification method, AOAC Official Method 992.18, (11) in the AOAC Independent study. A β-lysin CAMP
24
factor test was performed to augment the MICRO-ID
®
result.
25
26
GovVal Study: Detection of
Listeria monocytogenes
in Ready To Eat Foods
27
28
This validation study was conducted under the AOAC Research Institute GovVal program. The study was designed to compare
29
previously AOAC-approved rapid methods to the Health Protection Branch MFHPB–30 reference method for the detection of
Listeria
30
monocytogenes
in ready-to-eat meats. The specific matrices evaluated were liver paté, hot dogs, raw fermented sausage, sliced deli
31
turkey and sliced deli ham.
32
33
34
PTM Certification Report