OGA Supplement

Description

In this way physically stressed yeast cells give higher counts on media which depend upon broad-spectrum antibiotics rather than a low pH for selectivity.

Technique

Collect, dilute and prepare samples and volumes as required according to specifications, directives, official standard regulations and/or expected results.

Reconstitute 1 vial with the sterile diluent (distilled water) in aseptic conditions and add it to 500 mL of OGYE Agar Base cooled to 50 °C.

Do not overheat once supplemented.

Pour the complete medium into Petri dishes and, once solidified on a flat surface, spread the plates by streaking methodology or by spiral method.

Incubate the plates in aerobic atmosphere for 5 days at 20-25 °C, checking for formation of aerial mycelia after 2-5 days.

Incubation times longer than those mentioned above or different incubation temperatures may be required depending on the sample or the specifications.

After incubation, count all the colonies that have appeared on the surface of the agar.

Presumptive isolation of any pathogenic yeast and/or mould must be confirmed by further microbiological and biochemical tests.

Reconstitute the original freeze-dried vial by adding 6 mL of sterile distilled water.

Note: each vial is sufficient to supplement 500 mL of OGYE Agar Base.

Physical/chemical control

Microbiological control

Add 1 vial to 500 mL of medium base. DO NOT HEAT once supplemented.

Microbiological control according to ISO 11133:2014/Amd 1:2018.

Analytical methodology according to ISO 11133:2014/Amd 1:2018; A2:2020.

Aerobic. Incubation at 22.5 ± 2 °C up to 5 days (moulds and yeast).

Sterility control

100 mL TSB and 100 mL Thioglycollate.

Incubation 48 hours at 30-35 °C and 48 hours at 20-25 °C: NO GROWTH.

Check at 7 days after incubation in same conditions.

• DOWNES, F.P. & K. ITO (2001) Compendium of methods for the microbiological examination of foods. APHA. Washington DC. USA.
• ISO 11133:2014/Amd 1:2018. Microbiology of food, animal feed and water. Preparation, production, storage and performance testing of culture media.
• ISO 13681 Standard (1995) Enumeration of Yeasts and Moulds. Colony Count Technique.
• MacFADDIN, J.F. (1985) Media for isolation-cultivation-identification-maintenance of medical bacteria. William & Wilkins. Baltimore. MD. USA.
• MARSHALL, R.T. (1992) Standard methods for the examination of dairy products 16th ed. APHA. Washington DC, USA.
• MOSSEL, D.A.A., A.M.C. KLEYNEN-SEMMELING, H.M. VINCENTIE, H. BEERENS & M. CATSARAS (1970) Oxytetracycline-Glucose-Yeast Extract Agar for selective enumeration of moulds and yeasts in foods and clinical material. J. Appl. Bacteriol. 33:454-457.
• SABOURAUD, R. (1910) Les Teignes. Masson, Paris.