Microbiology

Selectively isolate and presumptively identify Clostridium perfringens in food samples with Thermo Scientific™ Oxoid™ Perfringens TSC Agar Base (Dehydrated). The medium can either be used on its own or with selective agents to make Tryptose Sulphite (TS) Agar, Tryptose Sulphite Cycloserine (TSC) agar or Shahadi Ferguson Perfringens (SPF) agar for the presumptive identification and enumeration of Clostridium perfringens.

Perfringens TSC/SFP Agar Base, Oxoid Composition

Agar Preparation:
To Prepare the Agar Base:
Suspend 23g in 500ml of distilled water and heat gently until the agar is completely dissolved. Sterilise by autoclaving at 121°C for 10 minutes. Allow the medium to cool to 50°C.

To Prepare Tryptose Sulphite Cycloserine Agar (TSC Agar):
To 500ml of Agar base cooled to 50°C add the rehydrated contents of 1 vial of TSC supplement (SR0088) and 25ml of egg yolk emulsion (SR0047). Mix well and pour into sterile Petri dishes.

To Prepare Egg Yolk Free TSC Agar:
To 500 ml of Agar base cooled to 50°C add the rehydrated contents of 1 vial of TSC supplement (SR0088). Mix well and pour into sterile Petri dishes.

To Prepare Shahidi-Ferguson Perfringens Agar (SFP Agar):
To 500 ml of Agar base cooled to 50°C add the rehydrated contents of 1 vial of SFP supplement (SR0093) and 25ml of egg yolk emulsion (SR0047) mix well and pour into sterile Petri dishes.

To Prepare Agar for an Overlay:
For TSC or SFP Agar used as an overlay, the egg yolk emulsion (SR0047) is omitted. Its inclusion does not improve the lecithinase reaction and diminishes the visibility of the colonies.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium at 2-8°C.

Precautions
Black colonies appearing on these two media may be organisms other than Clostridium perfringens.

Selectively isolate and differentiate Pseudomonas aeruginosa from a range of samples using Thermo Scientific™ Oxoid™ Cetrimide Agar (USP, EP) (Dehydrated). The medium contains magnesium chloride and potassium sulphate for improved pigment production and recovery of Pseudomonas aeruginosa while strongly suppressing Klebsiella, Proteus and Providencia spp. The medium conforms to European Pharmacopoeia for Microbial Limit Tests.

Cetrimide Agar (USP, EP) (Dehydrated), Oxoid Composition

Cetrimide Agar Preparation:
Suspend 45.3g of Pseudomonas Cetrimide Agar in 1 litre of distilled water. Add 10ml of glycerol and boil to dissolve completely. Sterilize by autoclaving at 121°C for 15 minutes. Cool the medium to approximately 50°C and pour into sterile Petri dishes.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared plates at 2-8°C.

Selectively isolate Pseudomonas species from a range of samples with Thermo Scientific™ Oxoid™ Pseudomonas Agar Base (Dehydrated). The medium is modification of King’s A Medium and contains magnesium chloride and potassium sulphate for improved pigment production and recovery of Pseudomonas aeruginosa while strongly suppressing Klebsiella, Proteus and Providencia spp.

Pseudomonas Agar Base (Dehydrated), Oxoid Composition

Agar Preparation:
To Prepare the Agar Base:
Suspend 24.2g of the agar base, in 500ml of distilled water. Add 5ml of glycerol. Bring to the boil to dissolve completely, sterilise by autoclaving at 121°C for 15 minutes. Allow the medium to cool to 50°C.

To Prepare Pseudomonas CN Agar:
To 500ml of agar base cooled to 50°C add the contents of 1 vial of Pseudomonas CN Supplement (SR0102) rehydrated as directed. Mix well and pour into sterile Petri dishes.

To Prepare Pseudomonas CFC Agar:
To 500ml of agar base cooled to 50°C add the contents of 1 vial of Pseudomonas CFC Supplement (SR0103) rehydrated as directed. Mix well and pour into sterile Petri dishes.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium at 2-8°C.

Precautions
Fresh media should be prepared as required. Molten agar should not be kept longer than 4 hours. Medium should not be stored and remelted. If swarming colonies of Proteus species are a problem in food samples then the incubation temperature can be lowered to 20°C for a period of 3-5 days. Chilled foods may carry a wide range of pseudomonads and the colonies on CFC Medium, incubated at lower temperatures, may be Pseudomonas fluorescens or Pseudomonas putida as well as Pseudomonas aeruginosa. Aeromonas species will also appear as pink/brown colonies, particularly from fish products.

• Oxoid Rose-Bengal Chloramphenicol Agar Base is a medium for the selective enumeration of yeast and molds from foods.
• Also available Chloramphenicol Selective Supplement, Part No. SR0078E.

Rose-Bengal Chloramphenicol Agar Base, Oxoid Composition

Rose-Bengal Chloramphenicol Agar, Oxoid Preparation:
Suspend 16.0g per 500ml (32.0g/l) of distilled water and bring to the boil to dissolve completely. Reconstitute one vial SR0078E per 500ml medium or one vial SR0078H per 2 litres medium, as directed. Add the vial contents to Rose Bengal Chloramphenicol Agar Base (CM0549) and mix gently. Autoclave at 121°C for 5 minutes. Cool to 50°C, mix gently and pour into Petri dishes.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium at 2-8°C away from light.
NB: Rose-Bengal photo-oxidises to form toxic compounds. Store plates of the medium in the dark and avoid exposure to light.

Precautions
It is essential to store plates of media containing Rose-Bengal in the dark to prevent toxic photo-oxidation of the dye. See above.
Identify moulds and yeasts by morphological appearance and microscopic examination. Colonies of bacteria and yeasts can be confused.

Selectively enumerate yeasts and molds from foodstuffs with Thermo Scientific™ Oxoid™ Oxytetracycline Glucose Yeast Extract Agar Base (Dehydrated). The medium is based upon the formulation described by Mossel et al. which utilizes oxytetracycline selectivity to provide increased counts of yeasts and molds compared to other media that utilize a low pH as a selective agent. Improve the recovery of physically stressed yeast cells on this neutral pH medium.

Oxytetracycline Glucose Yeast Extract Agar Base (Dehydrated), Oxoid Composition

Oxytetracycline Glucose Yeast Extract Agar, Oxoid Preparation:
Suspend 18.5g in 500ml of distilled water and bring gently to the boil to dissolve completely. Sterilise by autoclaving at 115°C for 10 minutes. Allow the medium to cool to 50°C and aseptically add the contents of one vial of Oxytetracycline GYE Selective Supplement (SR0073) reconstituted as directed. Mix thoroughly and pour into sterile Petri dishes. The pH of this medium should be 7.0±0.2 @ 25°C.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium at 2-8°C.

Precautions:
The lactic-acid bacteria are inhibited on this medium.

• Oxoid Perfringens OPSP Agar Base is used for the enumeration of Clostridium perfringens in foods.
• lso available Perfringens OPSP Supplement A, Part No. SR0076E and Perfringens OPSP Supplement B, Part No. SR0077E.

Perfringens OPSP Agar Base, Oxoid Composition

Perfringens OPSP Agar, Oxoid Preparation:
Suspend 22.8g in 500ml of distilled water and bring gently to the boil to dissolve completely. Sterilise by autoclaving at 121°C for 15 minutes. Allow to cool to 50°C and aseptically add the contents of one vial each of Perfringens Agar (OPSP) supplements A and B (SR0076 and SR0077) which have been rehydrated as directed. Mix well and pour into sterile dishes.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium at 2-8°C.

Precautions
The production of black colonies on this medium is a presumptive identification of Clostridium perfringens. Further identification tests must be carried out.

Oxoid Sabouraud Maltose Agar is used where maltose is the preferred carbohydrate source.

Sabouraud Maltose Agar, Oxoid Composition

Sabouraud Maltose Agar, Oxoid Preparation:
Suspend 65g in 1 litre of distilled water. Bring to the boil to dissolve completely. Sterilise by autoclaving at 121°C for 15 minutes. Mix well and pour in to sterile Petri dishes.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium at 2-8°C.

Precautions
Some of the pathogenic fungi may produce infective spores which are are easily dispersed into the laboratory. Such organisms should be examined only within a protective cabinet.
The combination of cycloheximide and chloramphenicol inhibits many pathogenic fungi. However, the mycelial phase of Histoplasma capsulatum, Paracoccidioides brasiliensis, Sporothrix schoenckii and Blastomyces dermatitidis is not inhibited by these antibiotics when incubated at 25-30°C .
Note the precautions in handling cycloheximide described in HAZARDS section.

• Oxoid Dermasel Agar Base is used for primary isolation and identification of dermatophyte fungi.
• Also available Dermasel Selective Supplement, Part No. SR0075E.

Dermasel Agar Base, Oxoid Composition

Dermasel Agar, Oxoid Preparation:
Suspend 44.5g in 1 litre of distilled water and heat gently to dissolve completely. Add the contents of 1 vial of Dermasel Selective Supplement SR0075, reconstituted as directed in the product insert, to each 500ml of medium to give a level of cycloheximide 0.4g/l and chloramphenicol 0.05g/l. Mix gently and sterilise by autoclaving at 121°C for 10 minutes. Avoid overheating at any time.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared agar plates at 2-8°C.

Precautions
This medium should not be used if agents causing systemic mycoses are being sought⁹. If such agents are suspected e.g. cryptococcus, histoplasma etc., either Dermasel Agar Base without antibiotic supplement must be used in parallel or Brain Heart Infusion Agar CM0375.
If the fungal agent sought is suspected to be nutritionally fastidious, the use of Brain Heart Infusion Agar is particularly helpful.

Oxoid SS Agar Modified (Salmonella Shigella Agar Modified) is used for the isolation of Salmonella species and Shigella spp.

Salmonella Shigella Agar Modified, Oxoid Composition

Salmonella Shigella Agar Modified, Oxoid Preparation:
Suspend 57g in 1 litre of distilled water. Bring to the boil with frequent agitation, and allow to simmer gently to dissolve the agar. DO NOT AUTOCLAVE. Cool to about 50°C mix well and pour into sterile Petri dishes.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium at 2-8°C.

An anaerobic enrichment broth for Staphylococcus aureus.

Giolitti-Cantoni Broth, Oxoid Composition

Giolitti-Cantoni Broth, Oxoid Preparation:
Suspend 54.2g in one litre of distilled water and heat gently to dissolve. Dispense 19ml amounts into 20 x 200mm test tubes and sterilise by autoclaving at 121°C for 15 minutes. Cool rapidly then aseptically add to each tube 0.3ml of a sterile solution of Potassium tellurite 3.5% SR0030.
The medium requires the addition of a 3.5% solution of Potassium tellurite when there is a direct addition of 1g of the sample to 19mls of broth. This level of Potassium tellurite is necessary to suppress the high numbers of contaminating organisms that could be expected.
The use of a diluted solution of Potassium tellurite is applicable when a 1 in 10 dilution of the food sample is carried out. In such cases the SR0030 should first be diluted 1 in 10 with sterile distilled water.
The addition of 0.1% Tween 80 can be recommended in order to improve recovery of heat injured Staphylococcus aureus cells e.g. from milk powder. 1g of Tween 80 should be added to 1 litre of CM0523 prior to autoclaving.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium at 2-8°C.

Oxoid Cary-Blair Transport Medium is a transport medium for gram-negative and anaerobic microorganisms.

Cary-Blair Transport Medium, Oxoid Composition

Cary-Blair Transport Medium, Oxoid Preparation:
Suspend 13.3g in 1 litre of distilled water and bring gently to the boil to dissolve the agar. Distribute into small, screw-cap bottles and sterilise by immersing in free-steam for 15 minutes. Allow to cool and tighten the screw caps to prevent water loss.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
The prepared medium should be stored away from light at 2-8°C or at room temperature (22-25°C) up to 19 months.

Precautions
The medium should not be incubated to check sterility, prior to use. This should be carried out on separate quality control samples.
The medium can maintain the viability of fastidious organisms for transport purposes but it should not be used as a storage or enrichment medium.
The results obtained from the medium are dependent on the quality of the specimen material. Commensal anaerobic organisms may overgrow in the medium and cause misleading results.

Pre-enrich food samples prior to the isolation of Salmonella species using Thermo Scientific™ Oxoid™ Buffered Peptone Water (Dehydrated). Buffered Peptone Water is a non-selective pre-enrichment medium. It also provides conditions for resuscitation of cells that have been injured by processes of food preservation.

Buffered Peptone Water, Oxoid Composition

Buffered Peptone Water, Oxoid Preparation:
Add 20g to 1 litre of distilled water. Mix well and distribute into final containers. Sterilise by autoclaving at 121°C for 15 minutes. It is extremely important that the distilled water used is of a high quality with a low mineral content/conductivity.

Storage conditions and Shelf life
Store dehydrated medium at 10-30°C and use before the expiry date of the label.
Store the prepared medium at room temperature.

Pre-enrich food samples prior to the isolation of Salmonella species using Thermo Scientific™ Oxoid™ Buffered Peptone Water (Dehydrated). Buffered Peptone Water is a non-selective pre-enrichment medium. It also provides conditions for resuscitation of cells that have been injured by processes of food preservation.

Buffered Peptone Water, Oxoid Composition

Buffered Peptone Water, Oxoid Preparation:
Add 20g to 1 litre of distilled water. Mix well and distribute into final containers. Sterilise by autoclaving at 121°C for 15 minutes. It is extremely important that the distilled water used is of a high quality with a low mineral content/conductivity.

Storage conditions and Shelf life
Store dehydrated medium at 10-30°C and use before the expiry date of the label.
Store the prepared medium at room temperature.

Buffered Peptone Water (Dehydrated), CM0509B (Oxoid) is a non-selective pre-enrichment medium that used to pre-enrich food samples prior to the isolation of Salmonella species. It also provides conditions for the resuscitation of cells that have been injured by processes of food preservation.

Buffered Peptone Water, Oxoid Composition

Buffered Peptone Water, Oxoid Preparation:
Add 20g to 1 litre of distilled water. Mix well and distribute into final containers. Sterilise by autoclaving at 121°C for 15 minutes. It is extremely important that the distilled water used is of a high quality with a low mineral content/conductivity.

Storage conditions and Shelf life
Store dehydrated medium at 10-30°C and use before the expiry date of the label.
Store the prepared medium at room temperature.

• Oxoid MacConkey Agar w/o Salt (Dehydrated) is a differential medium on which swarming of Proteus species is suppressed.
• For urine examination.

MacConkey Agar without Salt (Dehydrated), Oxoid Composition

MacConkey Agar, Oxoid Preparation:
Suspend 47g in 1 litre of distilled water. Bring to the boil to dissolve completely. Sterilise by autoclaving at 121°C for 15 minutes. Mix well before pouring. Dry the surface of the gel before inoculation.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared plates of medium at 2-8°C.

Precautions
The colonial characteristics described give presumptive identification only of the isolated organisms. It is necessary to subculture and carry out confirmation tests for final identification.
To enhance the pigment of suspected Staphylococcus aureus, hold the plates on the bench at ambient temperature for 12-18 hours.
This medium may produce a discrete precipitate on cold storage of 2 – 10°C. This in no way affects the performance of the medium.

Detect coliform organisms in water and milk examination with Thermo Scientific™ Oxoid™ MacConkey Broth Purple (Dehydrated). Bromocresol purple indicator in the medium provides more sensitive and definite indications of acid production as compared to neutral red indicator and is less inhibitory to Escherichia coli. The use of bromocresol purple corresponds to the alternative formulations recommended in ‘The Bacteriological Examination of Water Supplies’ and ‘International Standard for Drinking Water’.

MacConkey Broth Purple, Oxoid Composition

MacConkey Broth Purple, Oxoid Preparation:
To prepare single strength broth add 40g to 1 litre of distilled water. Distribute into containers fitted with fermentation (Durham) tubes. Sterilise by autoclaving at 121°C for 15 minutes.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium at room temperature.

Oxoid Tinsdale Agar Base is used for the isolation and identification of Corynebacterium diphtheriae.

Tinsdale Agar Base, Oxoid Composition

Tinsdale Agar, Oxoid Preparation:
Suspend 9g of agar base in 200ml of distilled water. Bring to the boil and dissolve completely. DO NOT AUTOCLAVE. Allow to cool to approximately 50°C and add the contents of one vial of Oxoid Tinsdale Supplement SR0065 reconstiuted as directed. Mix throughly and pour into sterile Petri dishes.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium at 2-8°C for not more than 4 days.

Precautions
Further tests must be carried out on colonies suspected as Corynebacterium diphtheriae, including cell morphology after sub-culture to Loeffler’s Medium and examination for toxin production.
Do not incubate Tinsdale’s Agar plates in enhanced CO2 atmosphere (5-10% v/v).

Detect and enumerate Enterobacteriaceae in food products with Thermo Scientific™ Oxoid™ Violet Red Bile Glucose Agar (Dehydrated). This glucose-containing selective medium gives reproducible counts of typical colonies for food safety analysis. In the examination of food stuffs, detection of the Enterobacteriaceae that ferment glucose to produce acid and/or gas has been recommended.

Violet Red Bile Glucose Agar (Dehydrated), Oxoid Composition

Violet Red Bile Glucose Agar (Dehydrated), Oxoid Preparation:
Suspend 38.5g in 1 litre of distilled water. Bring to the boil. Continue to boil for 2 minutes or for the minimum time necessary to dissolve completely and ensure that there are no remaining flecks of unmelted agar. No further sterilisation is necessary or desirable. Mix well and dispense into tubes or dishes.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium at 2-8°C and use as freshly as possible.

Precautions
This medium is not completely specific for Enterobacteriaceae, other organisms may grow e.g. Aeromonas. The selective activity of this medium diminishes after 24 hours incubation and organisms previously suppressed may exhibit growth. Medium for the pour-plate procedure should be freshly prepared, cooled to 47°C and used within 3 hours.

A modified medium requiring the addition of basic fuchsin to form Endo Agar.

• Oxoid Endo Agar is an APHA recommended medium for the confirmation of coliforms.
• Also available Basic Fuchsin Indicator, Part No. BR0050A.

Endo Agar Base, Oxoid Composition

Endo Agar, Oxoid Preparation:
Suspend 36g in 1 litre of distilled water. Add 6ml (or as directed by the supplier) of a 10% w/v solution of basic fuchsin BR0050 (50:50 ethanol/distilled water). Bring to the boil to dissolve completely. Sterilise by autoclaving at 121°C for 15 minutes. Mix well before pouring. Plates should be stored in the dark to preserve their pale pink colour.

BASIC FUCHSIN IS A POTENTIAL CARCINOGEN AND CARE SHOULD BE TAKEN TO AVOID INHALATION OF THE POWDERED DYE AND CONTAMINATION OF THE SKIN.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared plates at 2-8°C away from light.

Precautions
Weigh out the basic fuchsin (BR0050) in a fume cupboard and avoid inhalation of the powder or contamination of the skin.
Keep the prepared medium away from light to avoid photo-oxidation.
Endo Agar is quoted by the American Public Health Association as a `Standard Methods’ medium for use in water¹ and dairy products. Windle Taylor recommended the medium for the isolation and differentiation of coli-aerogenes bacteria from water.

Perform effortless testing using Thermo Scientific™ Oxoid™ Iso-Sensitest Broth (Dehydrated), a semi-defined medium specifically designed for antimicrobial susceptibility testing (AST). Iso-Sensitest Broth is carefully constructed to give reproducible results. It allows the growth of the majority of microorganisms without the need of further supplementation.

Iso-Sensitest Broth, Oxoid Composition

Iso-Sensitest Broth, Oxoid Preparation:
Add 23.4g to 1 litre of distilled water. Mix well and heat to dissolve. Distribute into tubes or bottles. Sterilise by autoclaving at 121°C for 15 minutes.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.

Thermo Scientific™ Oxoid Iso-Sensitest Agar is a semi-defined medium designed for antimicrobial susceptibility testing.

Iso-Sensitest Agar, Oxoid Composition

Iso-Sensitest Agar, Oxoid Preparation:
Suspend 31.4g in 1 litre of distilled water and bring to the boil to dissolve the agar. Sterilise by autoclaving at 121°C for 15 minutes.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium at 2-8° C and use as freshly as possible.

Isolate Salmonella and Shigella from clinical specimens and foods with selective Thermo Scientific™ Oxoid™ XLD Agar (Dehydrated). The medium relies on xylose fermentation, lysine decarboxylation and production of hydrogen sulphide for the primary differentiation of shigellae and salmonellae from non-pathogenic bacteria. The careful addition of sodium desoxycholate inhibits the growth of coliforms without decreasing the ability to support shigellae and salmonellae.

XLD Agar (Dehydrated), Oxoid Composition

XLD Agar (Dehydrated), Oxoid Preparation:
Suspend 53g in 1 litre of distilled water. Heat with frequent agitation until the medium boils. DO NOT OVERHEAT. Transfer immediately to a water bath at 50°C. Pour into sterile Petri dishes as soon as the medium has cooled.

It is important to avoid preparing large volumes which will cause prolonged heating.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium at 2-8°C.

Isolate Salmonella and Shigella from clinical specimens and foods with selective Thermo Scientific™ Oxoid™ XLD Agar (Dehydrated). The medium relies on xylose fermentation, lysine decarboxylation and production of hydrogen sulphide for the primary differentiation of shigellae and salmonellae from non-pathogenic bacteria. The careful addition of sodium desoxycholate inhibits the growth of coliforms without decreasing the ability to support shigellae and salmonellae.

XLD Agar (Dehydrated), Oxoid Composition

XLD Agar (Dehydrated), Oxoid Preparation:
Suspend 53g in 1 litre of distilled water. Heat with frequent agitation until the medium boils. DO NOT OVERHEAT. Transfer immediately to a water bath at 50°C. Pour into sterile Petri dishes as soon as the medium has cooled.

It is important to avoid preparing large volumes which will cause prolonged heating.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium at 2-8°C.

Detect coliform organisms in water, waste water and dairy products with selective Thermo Scientific™ Oxoid™ Lauryl Tryptose Broth (Dehydrated), while conforming to the formula detailed by American Public Health Association. Lauryl Tryptose Broth is designed to promote a rich growth and copious gas production from small inocula of coliform organisms.

Lauryl Tryptose Broth, Oxoid Composition

Lauryl Tryptose Broth, Oxoid Preparation:
Dissolve 35.6g in 1 litre of distilled water and distribute into containers with fermentation tubes (Durham). Sterilise by autoclaving at 121°C for 15 minutes.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium at room temperature.

Precautions
If stored at 2-8°C the broth will become cloudy or form a precipitate. This should clear at room temperature but gas formation is the criterion of growth not turbidity.