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1. Principle & application scope

Salmonellais a kind of intestinal bacteria that can cause food poisoning, enterogastritis, and typhoid etc, people who infected salmonella have the symptom of nausea, vomit, and diarrhea that could last for 7 days. Chicken, eggs and meat are especially high risk food to salmonella. Salmonella count plate which contains selective medium, special chromogenic reagent and bibulous gel could get the results after culturing for 15-24h. Salmonella count plate is very suitable for food manufacturers and institute of food hygiene inspection.

Executive standard : Food safety national standard ,

                                  Food microbiological examination: Salmonella (GB 4789.4)

2.  Using method

2.1 Sample preparation: Prepare the 1:10 solution by placing 25g or 25mL sample into 225mL sterile                                                saline.

2.2 Inoculation: Place the salmonella count plate onto sterile experiment table, uncover the film on the surface. Suck 1mL solution onto the plate, and then drop it slowly and evenly to the count plates. Cover the film gently and stand it for 10s to let the medium solidify. Inoculate two count plates for each sample, and at the same time do a blank control.

2.3 Culture

Pile up the count plates and place them back to the ziplock bags and seal them well. Place them in the incubator with transparent side up. The quantity of superimposed count plates should not be more than 12.  The temperation of culture is 36℃±1℃, and the time of culture is 15-24h.

3. Results

Salmonellawould show purplish red while other colonies would show blue after the culture. The sample which shows positive results should be veritified by other detection methods or take the sample to do at least one more test using salmonella count plate.

4. Report

Whether salmonella is detected from 25mL or 25g samples.

5.Additional explanatory note

5.1 Inoculating strain of salmonella (incl. H2S negative strains of salmonella) on these count plates will generate typical purple red bacterial plaque, while other enterobacter shows blue, and staphylococcus will not grow .

5.2 The count plates have high sensitivity ,and it can let colony grow when the dilute ratio is only 1.5*10-8. Clinic application shows the rate of positive detecting results is 1.84‰ higher than separation culture ,and the accuracy rate is increasing 13%.

5.3 Dispose the used count plates timely according to biology safety waste treatment rule because there are live bacteria on them.