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SUBMITTED 050113
AOAC International Pre-Collaborative Study Report
Use of the ANSR
TM
Salmonella
Test as a Confirmatory Procedure for Identification of
Salmonella
spp. from Colony Picks from Selective/Differential Agar Media
Maximilian Botimer, Carolyn Jagadics, Paul Norton, Mark Mozola*, and Jennifer Rice
Neogen Corporation, 620 Lesher Place, Lansing, MI 48912
* Study Director
, mmozola@neogen.comIntroduction
The ANSR
Salmonella
assay was originally developed as a screening test for food and environmental
samples following broth culture enrichment. The method has been granted Performance Tested
Method
SM
status by the AOAC Research Institute for testing of a wide variety of food and environmental
samples (certificate no. 061203; [1, 2]). While useful as a screening method, the potential advantages of
the assay as a confirmatory test for presumptive colonies taken from selective/differential agar plates
are compelling. First, a presumptive colony can be definitively identified as
Salmonella
spp. in 30 min.,
compared with 24-48 h required by typical biochemical identification methods. Second, there is no
requirement that the colony pick be pure, i.e., unlike biochemical identification methods, the
contaminating presence of non-
Salmonella
bacteria will not interfere with the ability of the assay to
identify the presence of
Salmonella
spp. in the sample. Finally, the method is cost effective, with
minimal equipment requirements and an assay platform scaled for 1-16 determinations per
experimental run.
As part of the PTM study of the screening method, inclusivity was assessed using a panel of 113 strains
of
S
.
enterica
and
S
.
bongori
representing 109 serovars. With the single exception of a strain of the rare
serovar
S
. Weslaco, all strains were detected by the ANSR assay when tested at a concentration of
approximately 1 x 10
5
cfu/mL, which is 10 to 100-fold above the limit of detection of the assay [1].
Exclusivity testing was conducted using a panel of 38 strains of non-salmonellae, primarily closely
related members of the Enterobacteriaceae and representing 15 genera and 37 species. Strains were
tested after growth to high titer (~ 1 x 10
9
cfu/mL) in non-selective tryptic soy broth. All tests produced
1