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Food and Nutrition

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Procedure for the Isolation of Salmonella species by the Modified Semi-solid Rappaport Vassiliadis (MSRV) Method

Table of Contents

5. COLLECTION OF SAMPLES

See Appendix A of Volume 3.

6. EQUIPMENT AND MATERIALS

The media listed below (1 to 4) are commercially available and are to be prepared and sterilized according to the manufacturer's instructions. See also Appendix G of Volume 3, reference 8.1 or other suitable source, for the formulae of individual media.

Note: If the analyst uses any variations of the media listed here (either product that is commercially available or made from scratch), it is the responsibility of the analyst or Laboratory Supervisor to ensure equivalency.

1) Modified Semi-Solid Rappaport Vassiliadis (MSRV) plates

2) Buffered Peptone Water (BPW), Nutrient Broth (NB) or other pre-enrichment media as specified for specific commodities (see MFHPB-20, Table 3)

3) MacConkey agar plates

4) Tetrathionate Brilliant Green broth (TBG)

5) Confirmatory test media (such as, Triple Sugar Iron Agar slants and Lysine Iron Agar slants) as required (see MFHPB-20)

6) Stomacher bags for homogenate

7) Large, strong plastic bags for poultry rinsing technique

8) Incubators, thermostatically-controlled, 35 and 4°C

Note: It is the responsibility of each laboratory to ensure that incubators or waterbaths are maintained at the recommended temperatures. Where 35°C is recommended in the text of the method, the incubators may be at 35 +/-1.0°C. Similarly, lower temperatures of 30 or 25 may be +/- 1.0°C. However, where higher temperatures are recommended, such as 43 or 45.5°C, it is imperative that the incubators or waterbaths be maintained within 0.5°C due to potential lethality of higher temperatures on the microorganism being isolated.

9) Control Cultures - Positive: Salmonella Typhimurium (ATCC #14028) or S. Berta (ATCC #8392) or other motile Salmonella spp.; Negative: E. coli or other non-salmonellae

10) Polyvalent Antisera and/or specific somatic antisera

11) Confirmation Kits: e.g., API-20E, Micro-ID, Enterotube, Vitek or other commercially available kits or procedures (optional)

7. PROCEDURE

Each sample unit may be analyzed individually or the analytical units may be combined where requirements of the applicable sampling plan can be met.

7.1 Handling of Sample Units

7.1.1 In the laboratory prior to analysis, except for shelf-stable foods, keep sample units refrigerated (0-5°C) or frozen, depending on the nature of the product. Thaw frozen samples in a refrigerator or under time and temperature conditions which prevent microbial growth or death.

7.1.2 Analyze sample units as soon as possible after their receipt in the laboratory.

7.2 Preparation for Analysis

7.2.1 Have ready sterile pre-enrichment media.

7.2.2 Clean the surface of the working area with a suitable disinfectant.