GB 4789.8-2016National food safety standard - Food Microbiological Examination - Yersinia Enterocolitica (English PDF)

Foreword

This Standard replaces GB 4789.8-2008, National Food Safety Standard – Food

Microbiological Examination – Yersinia Enterocolitica.

Compared with GB 4789.8-2008, the major changes of this Standard are as follows.

-- it changes the standard name into "National Food Safety Standard – Food

Microbiological Examination – Yersinia Enterocolitica";

-- it modifies the morphological description of typical colonies;

-- it deletes the commercial names in biochemical identification;

-- it describes the method for serologic identification.

National Food Safety Standard – Food Microbiological

Examination – Yersinia Enterocolitica

1 Application Scope

This Standard specifies the method for the test of Yersinia enterocolitica in foods.

This Standard applies to the test of Yersinia enterocolitica in foods.

2 Apparatus and Materials

In addition to the conventional sterilization and culture equipment in a microbiological

lab, other apparatus and materials are as follows.

3 Culture Media and Reagents

15 min at 121°C.

A.5.2.2 After preparing the other sugar fermentation tubes in accordance with the

constituents above; split charging to 100 mL each flask; carry out autoclaved

sterilization for 15 min at 121°C. Use different kinds of sugar to prepare 10% solutions

and meanwhile carry out autoclaved sterilization. Add 5 mL of sugar solution to 100

mL of medium; split charging to small test tubes by aseptic technique. If the sugar is

not pure, it will be hydrolyzed by itself after heating, so sterilization shall be carried out

by filtering.

A.5.3 Test method

Pick a small amount of culture from the agar slant to inoculate to incubate at 26°C ±

1°C; observe for 2 d ~ 3 d, as a general rule. Torpid reaction needs to be observed for

14 d ~ 30 d.

A.6 Ornithine decarboxylase test medium

A.6.1 Constituents

Peptone 5.0 g

Yeast extract 3.0 g

Glucose 1.0 g

Distilled water 1 000 mL

1.6% bromocresol purple-ethyl alcohol solution 1.0 mL

L-ornithine or DL-ornithine 0.5 g/100 mL or 1 g/100 mL

A.6.2 Preparation

After heating to dissolve all constituents except ornithine; split charging 100 mL of

ornithine to each flask. Add L-ornithine to 0.5% or DL- ornithine to 1%. Then correct

the pH value to 6.8. Do not add ornithine to control medium. Split charging to sterile

small test tubes, 0.5 mL each tube; add dropwise one layer of liquid paraffin on the top;

carry out autoclaved sterilization for 10 min at 115°C.

A.6.3 Test method

Pick culture from the agar slant for inoculation; incubate for 18 h ~ 24 h at 26°C ± 1°C;

observe the results. The ornithine decarboxylase positive ones generate alkali, so the

immediately or within several minutes; in case of a negative reaction, observation shall

be performed after incubation for 4 h at 36°C ± 1°C.

A.9 Alkali treatment solution

A.9.1 0.5% sodium chloride solution

Sodium chloride 0.5 g

Distilled water 100 mL

Carry out autoclaved sterilization for 15 min at 121°C.

A.9.2 0.5% potassium hydroxide

Potassium hydroxide 0.5 g

Distilled water 100 mL

Carry out autoclaved sterilization for 15 min at 121°C.

A.9.3 Preparation

Mix up an equal quantity of 0.5% sodium chloride and 0.5% potassium hydroxide.

A.10 Urea medium

A.10.1 Constituents

Urea 20.0 g

Yeast extract 0.1 g

Potassium dihydrogen phosphate 0.091 g

Disodium hydrogen phosphate 0.095 g

Phenol red 0.01 g

Distilled water 1 000 mL

A.10.2 Preparation

Dissolve the constituents in A.10.1 in distilled water; correct the pH value to 6.8 ± 0.2.

Do not heat; filter for sterilization; split charging to sterile small test tubes by aseptic

technique, about 3 mL each tube.

A.10.3 Test method

Pick agar culture to inoculate to urea medium; incubate for 24 h at 26°C ± 1°C. The

urease positive ones generate alkali, so it makes the medium turn red.

A.11 Nutrient agar

A.11.1 Constituents

Peptone 10.0 g

Beef extract 3 g

Sodium chloride 5 g

Agar 15 g

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