SOP: Preparation of Agars, Broths and Other Reagents — Media Glossary, Section U

GIFSQ — Global Institute for Food Safety & Quality

Principle

This document gives the laboratory formulations of the agars, broths and other reagents in the Media Glossary that begin with the letter U. For each medium it lists the basal medium ingredients with their quantities, any supplement, and the complete-medium preparation steps, so that the medium can be prepared in the laboratory and made available to the analytical methods of the compendium.

Apparatus required

• Analytical balance
• Autoclave
• Heating equipment for gentle heating and boiling
• Sterile filter apparatus
• Screw-cap tubes

Universal Preenrichment Broth

Basal medium

• Tryptone — 5.0 g
• Proteose peptone — 5.0 g
• Potassium phosphate, monobasic (KH₂PO₄) — 15.0 g
• Potassium phosphate, dibasic (K₂HPO₄) — 7.0 g
• Sodium chloride (NaCl) — 5.0 g
• Dextrose — 0.5 g
• Magnesium sulfate (MgSO₄) — 0.25 g
• Ferric ammonium citrate — 0.1 g
• Sodium pyruvate (C₃H₃O₃Na) — 0.2 g
• Distilled water — 1.0 L
• pH: 6.3 ± 0.2

Complete medium

• Suspend the basal medium ingredients in 1.0 L of distilled water
  ↓
• Heat gently until completely dissolved
  ↓
• Autoclave at 121 °C for 15 min

Urea Agar (Christensen’s)

Basal medium

• Peptone — 1.0 g
• Dextrose — 1.0 g
• Sodium chloride (NaCl) — 5.0 g
• Potassium phosphate, monobasic (KH₂PO₄) — 2.0 g
• Phenol red — 0.012 g
• Agar — 15.0 g
• Distilled water — 900 mL
• pH: 6.8 ± 0.2

Supplement (urea solution)

• Urea — 20.0 g
• Distilled water — 100 mL

Complete medium

• Suspend the basal medium ingredients in 900 mL of distilled water
  ↓
• Autoclave at 121 °C for 15 min and cool to 45–50 °C
  ↓
• Dissolve 20.0 g of urea in 100 mL of distilled water and sterilize by filtration
  ↓
• Aseptically add the 100 mL of urea solution to the 900 mL of tempered basal medium
  ↓
• Dispense suitable volumes of the complete medium into tubes, to obtain deep butts upon cooling in a slanted position

UVM 1 and UVM 2 (University of Vermont Listeria Enrichment Broth)

• See Listeria Enrichment Broth

References

• Health Canada, Compendium of Analytical Methods, Volume 1, Appendix G — Glossary of Agars, Broths and Other Reagents, Section U (January 2006)