7.3.1 To ensure a truly representative analytical unit, agitate liquids or free flowing materials until the contents are homogeneous. If the sample unit is a solid, obtain the analytical unit by taking a portion from several locations within the sample unit. To reduce the workload, the analytical units may be combined for analysis. It is recommended that a composite contain not more than five analytical units.

7.3.2 Whole poultry

Place whole carcass, including giblets and drippings, if present, into a large, heavy sterile plastic bag using sterile technique. Add 1000 mL BPW or NB pre-enrichment for broiler chickens or 1500 mL for turkey carcasses and shake vigorously for 30 sec, ensuring that the entire surface and cavities of the sample come into contact with the broth. Remove the carcass from the broth, allowing fluid from the cavities of the carcass to drain into the plastic bag.

7.3.3 Fluid samples (blood plasma, chill tank water, etc.)

Aseptically add 25 mL (or sample volume required to maintain a 1:10 final dilution) to 225 mL of BPW or NB.

7.3.4 Raw meats

If not being tested for other organisms, a rinse technique similar to that described for poultry may be used with a 100 g sample and 200 mL NB or BPW. Alternately, a 25 g sample and 225 mL of pre-enrichment may be macerated by stomaching.

7.3.5 Animal feeds or feed ingredients, environmental samples (dry samples, dust, etc. or swatches)

Equilibrate the 25 g, 100 g (or sample weight) to maintain a 1:10 final dilution, in 2 volumes of NB or BPW for 1 h at 35°C. Add another 7 volumes of pre-enrichment broth and stomach.

7.3.6 For other samples, see MFHPB-20, Table 3.

7.3.7 Incubate the inoculated pre-enrichment broth in the plastic bag or the original broth container for 18 - 24 h at 35°C.

7.3.8 Inoculate the control cultures into tubes of the same pre-enrichment being used for the analysis. Use these control cultures to inoculate all subsequent media.

7.3.9 Inoculate 0.1 mL of the pre-enrichment broth on one side of an MSRV plate, a few millimeters from the edge. Similarly inoculate the positive and negative control broths onto additional plates.

7.3.10 Stack MSRV plates on trays to a maximum of 3 in height and incubate upright in a high moisture incubator at 42°C for 24 - 72 h.

7.3.11 Examine the plates at 24 h ± 2 h (with the aid of a viewing lamp, if required). Measure the distance from the edge of the inoculation point to the farthest boundary of migration. If migration is not evident or is less than 20 mm, re-incubate and re-examine the plates one or more times as appropriate, from 48 h ± 4 h to a maximum of 72 h ± 6 h incubation (this will allow further resuscitation of injured Salmonella in processed foods and stressed samples). At this point, the MSRV is considered negative for Salmonella if migration is still < 20 mm.

7.3.12 From the outer most edge of the migration area (i.e, farthest away from the inoculation point), pick a portion of the growth and inoculate a plate of MacConkey Agar for isolated colonies. Incubate at 35°C for 18-24 h. Select isolated colonies from the MacConkey plate for confirmatory testing.

7.3.13 Refer to MFHPB-20 for confirmatory testing methodology.

7.3.14 Pipette 1.0 mL of the pre-enrichment broth into 9.0 mL of Tetrathionate Brilliant Green broth (TBG). Incubate at 42°C for 24 h ± 2 h.

7.3.15 Inoculate an MSRV plate as in 7.3.9 and continue with steps 7.3.10 to 7.3.13.

If the zone of migration is greater than 20 mm, the biochemical reactions are typical for Salmonella spp. (see MFHPB-20, Table 4) and the serology is positive, the isolate is considered positive for Salmonella spp.