3MTMTECRA SalmonellaVisual Immunoassay (VIA) - AOAC 998.09

SCOPE

These methods are applicable to:

Raw meats, carcass swabs and food in general;

Methods differ in the selective liquid enrichment broths and incubation time/temperatures used.

PRINCIPLES

The detection of Salmonella spp. is broken down into stages as follows:

Pre-enrichment

A 1:10 dilution of the sample must be pre-enriched in buffered peptone water at 37 ± 1C for 18 ± 2 h. Buffered peptone water should be warmed to room temperature or to 37C for large volumes. For carcass sponges, buffered peptone water is added to the moistened sponge to bring the total volume to 60-100 ml and the sample incubated at 37 ± 1C for 18 ± 2 h. In the case of sponges BPW need not be warmed to room temperature before being used to re-hydrate the sponge, for all subsequent additions BPW should be warmed to room temperature.

Selective enrichment

Culture from the pre-enrichment broth is inoculated into Rappaport-Vassiliadis R10 broth and tetrathionate (TT) broth incubated at 41-43 C for 16-20 h. Store all broths at 2-8C for possible cultural confirmation using AS 5013.10.

Post-enrichment

Inoculate cultures obtained from the selective enrichment into M broth and incubate at 35-37C for 6 h. Store all broths at 2-8C for possible cultural confirmation using AS 5013.10.

Enzyme immunoassay

Follow the manufacturer’s instructions.

Cultural confirmation

Using retained selective enrichment broths and M-broths, proceed with Salmonella analysis as per AS 5014.10-2004 (starting from ‘Plating out and Identification’). Confirmation carried out at an ‘off-site’ laboratory must be from retained BPW enrichment or M-broths.

Issue 2017 01 10

Export Standards Branch | Exports Division Page 1 of 2

Department of Agriculture and Water Resources

3MTM TECRASalmonellaVIA –AOAC 998.09

CHECKLIST

Pre-enrichment / Is the buffered peptone water warmed to room temperature (to 37C for large quantities)?
Is the correct amount of enrichment broth used for the weight of sample analysed?
Is pre-enrichment done at 37 ± 1C for 18 ± 2 h?
Is a positive control run with each batch of samples analysed?
Are reference cultures inoculated into primary enrichment broth at a level of 10 to 100 cells?
Selective-enrichment / Are selective enrichment broths incubated at the appropriate temperature?
Are selective broths within their use-by-date?
Post-enrichment / Is M broth incubated at 35-37C for 6 h?
Are all selective enrichments stored correctly for possible cultural confirmation?
Immunoassay / Are the manufacturer’s instructions available?
Cultural confirmation / Is Salmonella isolated in-house from enrichment broths?
(if applicable) / If an external laboratory is used is it department approved?
BPW should be supplied to off-site laboratories for confirmation following AS 5013.10
Are Salmonella confirmed using AS 5013.10 (with appropriate selective agar plates)?

Issue 2017 01 10

Export Standards Branch | Exports Division Page 1 of 2

Department of Agriculture and Water Resources