AOAC RI ERP Final Action Recommendations

SUBMITTED 050113

Results and Discussion

Results are presented in Tables 1 and 2. All 113

Salmonella

spp. strains tested produced

positiveresults(“

Salmonella

spp.”) from all 7 selective/differential agar media with a singleexception.

The known non-inclusive strain of

. Weslaco produced negative results from all agar media tested.A

second strain of

. Weslaco produced positive results from all agar media. Overall inclusivity of the

ANSR confirmation method was 99.1%. Excluding the single non-inclusive strain, all 784 tests performed

on inclusivity strains produced positive results, for accuracy of 100%.

Of the 266 plates streaked with exclusivity strains, there were 15 cases of no growth and no ANSR test

performed (see Table 2). Of251 ANSR tests performed on exclusivity strains, 248produced negative

results (“not

Salmonella

spp.”)for overall accuracy on exclusivity strains of 98.8%. A colony of

Enterobacter intermedia

from DMLIA agar, and a colony of

Escherichia hermanii

from XLT4 agar

produced weakly positive, atypical ANSR fluorescence curves. A colony of

Edwardsiella tarda

from XLD

agar produced a strong positive ANSR curve. Re-tests of these strain/colony combinations all produced

negative results. The cause of the two atypical curves is not known. The aberrant strong positive curve

suggests a cross-contamination event or a sample handling or pipetting error.

Considering the total of 784 results on inclusivity stains (non-inclusive

. Weslaco strain excluded) and

251 results on exclusivity strains, overall accuracy of the ANSR confirmation method in initial testing was

99.7%.

Example assay curves for positive and negative results are shown in Fig. 1. Almost without exception,

assay curves generated for

Salmonella

spp. were very robust and of the type shown in the example.

Recommendations

Based on results of this pre-collaborative study, it is recommended that the ANSR

Salmonella

test

application for identification of

Salmonella

spp. from colony picks be subjected to inter-laboratory

collaborative study.