Microbiology

Cultivate and isolate fastidious microorganisms with clearly visible hemolytic reactions with Thermo Scientific™ Oxoid™ Columbia Blood Agar Base (Dehydrated) when used with whole defibrinated blood (SR0050). Columbia Blood Agar Base is an ideal base medium for preparation of blood agar, chocolate agar and for preparation of various selective and identification media.

Columbia Blood Agar Base, Oxoid Composition

Columbia Blood Agar, Oxoid Preparation:
Add 39g to 1 litre of distilled water. Boil to dissolve the medium completely. Sterilise by autoclaving at 121°C for 15 minutes. Cool to 50°C and add 5% sterile defibrinated blood.

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
Brucella cultures are highly infective and must be handled under properly protected conditions. Incubate in 5-10% carbon dioxide atmosphere for 24-48 hours.
Campylobacter species are best grown at 42°C (except Campylobacter fetus subsp. fetus) in a micro-aerophilic atmosphere (Oxoid Campylobacter Gas Generating Kit BR0056 or BR0060 or CampyGen CN0025/CN0035).
Staph./Strep. supplemented plates should be incubated aerobically at 35°C for 18 hours. Incubation in carbon dioxide- enriched air will cause inhibition of staphylococcal growth.
Streptococcus Selective Supplement SR0126 supplemented plates may be incubated aerobically or anaerobically at 35°C for 18 hours.
Prepared plates of both supplemented media should be used within 18 hours of preparation for maximum selectivity. Gardnerella supplemented plates should be incubated at 35°C for 48 hours in an atmosphere containing 7% carbon dioxide.
Carry out confirmatory tests on all colonies from horse blood medium and on beta-haemolytic colonies from human or rabbit blood medium.
Incubate plates of Clostridium E-Y Agar anaerobically at 35°C for 18 hours, look for lecithinase activity (pearly layer) and for proteolysis. Lecithinase activity is inhibited in the presence of specific anti-toxin.

Select and identify salmonellae (other than Salmonella Typhi) from food, feed and water samples with Thermo Scientific™ Oxoid™ Modified Brilliant Green Agar (Dehydrated). The modified formula provides improved inhibition of Escherichia coli and Proteus species. The medium has been widely assessed in Europe and has been used in ISO standards.

Brilliant Green Agar (Modified), Oxoid Composition

Brilliant Green Agar (Modified), Oxoid Preparation:
Suspend 52g in 1 litre of distilled water. Heat gently with occasional agitation and bring just to the boil to dissolve the medium completely. DO NOT AUTOCLAVE. Cool to 50°C, mix well and pour plates.

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
Lactose-fermenting salmonellae may be present in foods.
Salmonella typhi and Shigella species may not grow on this medium.
Proteus, Citrobacter and Pseudomonas species may mimic enteric pathogens by producing small red colonies.

Determine the plate counts of microorganisms in food, dairy samples, waste water and other material of sanitary importance with Thermo Scientific™ Oxoid™ Plate Count Agar (Dehydrated). Plate Count Agar was developed by Buchbinder et al which is recommended by APHA, AOAC and PHLS. The quality control of Plate Count Agar (APHA) includes testing in accordance with ISO 11133:2014.

Plate Count Agar (Dehydrated), Oxoid Composition

Plate Count Agar (Dehydrated), Oxoid Preparation:
Add 17.5g to 1 litre of distilled water. Dissolve by bringing to the boil with frequent stirring, mix and distribute into final containers. 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 plates at 2-8°C.

Detect microbial deoxyribonuclease enzymes, particularly from staphylococci, with Thermo Scientific™ Oxoid™ DNASE Agar (Dehydrated). A DNase (deoxyribonuclease) is any enzyme that catalyzes the cleavage of phosphodiester linkages of DNA leading to its degradation. The organisms producing DNase enzymes in sufficient quantities to hydrolyze DNA will show clear zones around the colonies. The medium is mainly used in the identification of staphylococci but may also be used for the detection of DNase activity in other organisms.

DNASE Agar, Oxoid Composition

DNASE Agar, Oxoid Preparation:
Suspend 39g in 1 litre of distilled water and bring to the boil to dissolve completely. 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 plates of medium at 2-8°C.

Precautions
The DNase reaction for staphylococci is an indication of pathogenicity, it cannot be used as the sole criterion for identification.
Small zones of clearing may be caused by other enzymes or organic acid production.
Other organisms than staphylococci, Serratia and aeromonads can produce DNases.
Once the hydrochloric acid has been applied to the medium the plate must be read within a few minutes and further testing cannot be carried out by re-incubation.
The methyl green must be purified by extraction with chloroform.
Toluidine blue varies in performance according to source.
Merck Toluidine blue 1273 is satisfactory. Note that this dye cannot be used for Gram positive organisms.

Enrich Enterobacteriaceae in bacteriological examination of foods and animal feed stuffs with Thermo Scientific™ Oxoid™ EE Broth (Buffered Glucose Brilliant Green Bile Broth) (Dehydrated). This medium is more inhibitory to non-Enterobacteriaceae than other non-selective media e.g. Mannitol broth or Lactose broth by virtue of the presence of brilliant green and bile salts in the preparation.

EE Broth, Oxoid Composition

EE Broth, Oxoid Preparation:
Add 43.5g to 1 litre of distilled water. Distribute 100ml quantities in 250ml flasks and heat at 100°C for 30 minutes only. Cool rapidly in cold running water. This medium is heat sensitive. DO NOT AUTOCLAVE.

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
Avoid overheating the medium, especially the double-strength broth.

• Oxoid WL Nutrient Agar is used for the determination of the microbiological flora in brewing and fermentation processes.
• Also available Cycloheximide 0.1% Solution, Part No. SR0222C.

WL Nutrient Agar, Oxoid Composition

WL Nutrient Agar, Oxoid Preparation:
Suspend 75g in 1 litre of distilled water. Bring to the boil to dissolve completely. Sterilise by autoclaving at 121°C for 15 minutes. If required the pH may be adjusted to 6.5 by the addition of 1% sodium bicarbonate solution.

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
When handling cycloheximide observe the precautions to be taken under HAZARDS.

Isolate, enumerate and differentiate urinary pathogens with Thermo Scientific™ Oxoid™ C.L.E.D. Medium (Dehydrated). Cystine-Lactose-Electrolyte-Deficient (CLED) Medium which provides good colonial differentiation, clear diagnostic characteristics and prevents swarming of Proteus spp. due to the electrolyte deficiency in the formulation.

C.L.E.D. Medium, Oxoid Composition

C.L.E.D. Medium, Oxoid Preparation:
Suspend 36.2g 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.

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

Differentiate Enterobacteriaceae according to their ability to ferment lactose, sucrose, and glucose, and to produce hydrogen sulphide using Thermo Scientific™ Oxoid™ Triple Sugar Iron Agar (Dehydrated). The Triple Sugar Iron Agar is based on Kligler Iron Agar, additionally, it contains sucrose for the detection of sucrose fermenting species.

Triple Sugar Iron Agar, Oxoid Composition

Triple Sugar Iron Agar, Oxoid Preparation:
Suspend 65g in 1 litre of distilled water. Bring to the boil to dissolve completely. Mix well and distribute. Sterilise by autoclaving at 121°C for 15 minutes. Allow the medium to set in sloped form with a butt about 1 in.deep.

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.

Baird Parker Agar Base, Oxoid is suitable for the isolation and enumeration of Staphylococcus aureus, with high selectivity and sensitivity. It contains carefully balanced selective inhibitory agents, glycine, lithium, and tellurite, to suppress the growth of most of the bacteria present in foods without inhibiting coagulase-positive staphylococci. The presence of egg yolk emulsion and sodium pyruvate aid the recovery of damaged cells for presumptive identification of Staphylococcus aureus in food specimens.

Baird Parker Agar Base, Oxoid Preparation:

Suspend 6.3g of Baird-Parker Agar Base (RPF) in 90ml of distilled water. Bring to the boil to dissolve completely. Sterilise by autoclaving at 121ºC for 15 minutes. Cool to 48ºC and add 1 vial of RPF Supplement (SR0122A), reconstituted as directed. Mix well and pour plates.

Storage Conditions and Shelf Life
Store the dehydrated medium at 10-30°C and RPF Supplement below 0°C. Use before the expiry date on the label.
Prepared plates of the medium are best used freshly prepared.

Precautions
Regard all suspicious colonies as Staphylococcus aureus regardless of negative reactions in the medium and carry out further tests.
Colonies of some contaminating organisms growing in close proximity to the coagulase positive colonies may partially digest the coagulase halo reaction.

Cultivate and isolate fastidious pathogens and other microorganisms with Thermo Scientific™ Oxoid™ Blood Agar Base No. 2 (Dehydrated). The specially designed formulation meets the need for a nutritious blood agar which permits maximum recovery of delicate organisms without interfering with their hemolytic reactions. Without any additions, the medium can be used for short-term maintenance of stock cultures. And with the addition of blood, the medium becomes suitable for the determination of the hemolytic reactions which are important diagnostic criteria for many organisms.

Blood Agar Base No. 2, Oxoid Composition

Blood Agar Base No. 2, Oxoid Preparation:
Suspend 40g in 1 litre of distilled water. Bring to the boil to dissolve completely. Sterilise by autoclaving at 121°C for 15 minutes. Cool to 45-50°C and add 7% sterile blood.

Mix with gentle rotation and pour into sterile dishes or other containers.

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
Brucella cultures are highly infective and must be handled under properly protected conditions. Incubate in 5-10% carbon dioxide atmosphere for 24-48 hours.

Oxoid Brilliant Green Agar (Kauffmann Medium) is used for increased recovery and selective isolation of Salmonella spp. other than S. Typhi.

• Also available Sulphamandelate Supplement, Part No. SR0087E

Brilliant Green Agar, Oxoid Composition

Brilliant Green Agar, Oxoid Preparation:
Suspend 50g in 1 litre of distilled water. Bring to the boil to dissolve completely. 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 plates of medium at 2-8°C.

Precautions
Lactose-fermenting salmonellae may be present in foods.
Salmonella typhi and Shigella species may not grow on this medium.
Proteus, Citrobacter and Pseudomonas species may mimic enteric pathogens by producing small red colonies.

Diagnostic Sensitivity Test Agar was developed in Oxoid as a dual purpose medium which would satisfy both diagnostic and susceptibility requirements.

Diagnostic Sensitivity Test Agar, Oxoid Composition

Diagnostic Sensitivity Test Agar, Oxoid Preparation:
Add 40 g to 1 litre of distilled water. Bring to the boil to dissolve completely. Sterilise by autoclaving at 121°C for 15 minutes.
For blood agar, cool the base to 50°C and add 7% of Defibrinated Horse Blood SR0050. Mix with gentle rotation and pour into Petri dishes (12 ml for a 9 cm dish) or other containers.
RECONSTITUTION AND MIXING SHOULD BE PERFORMED IN A FLASK AT LEAST 2.5 TIMES THE VOLUME OF MEDIUM TO ENSURE ADEQUATE AERATION OF THE BLOOD.

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
Diagnostic Sensitivity Test Agar has reduced thymidine activity and this will affect its performance as a primary isolation medium.

Oxoid Azide Blood Agar Base is a selective media for the detection and isolation of streptococci and staphylococci from feces, sewage and other specimens.

Azide Blood Agar Base, Oxoid Composition

Azide Blood Agar Base Oxoid Preparation:
Suspend 30g in 1 litre of distilled water and bring to the boil to dissolve completely. Sterilise by autoclaving at 121°C for 15 minutes. For azide blood agar, cool to 45-50°C and add 5% of sterile blood.

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

Precautions
Proteus and Escherichia species may not always be inhibited on the Edward’s formulation.
Always use a light inoculum for best selective results.
Anaerobic incubation will enhance haemolytic reactions.
Haemolytic reactions will not be typical on Packer’s modification of Azide Blood Agar Base. Streptococcus lactis will not grow on Packer’s modification with 5% sheep blood.
Read the section on Hazard Precautions for azide-containing media.

Wort Agar is a general purpose mycological medium, equivalent to the medium described by Parfitt and especially suitable for the cultivation and enumeration of yeasts. The medium which duplicates the composition of natural wort, is of an acidity which is optimal for many yeasts but inhibitory to most bacteria. Parfitt investigated the relative merits of wort agar and other media for the count of yeasts and moulds in butter, and recommended the use of dehydrated whey, malt or wort agar for the purpose. Scarr employed a modified wort agar (’osmophilic agar’) for the examination of sugar products for osmophilic yeasts. Scarr’s technique is also used for the determination of osmophilic yeasts occurring in materials used in the manufacture of soft drinks.

Wort Agar, Oxoid Composition

Wort Agar, Oxoid Preparation:
Suspend 50g in 1 litre of distilled water and bring to the boil to dissolve completely. Sterilise by autoclaving at 121°C for 15 minutes.
PROLONGED OR EXCESSIVE HEATING WILL DIMINISH THE GEL STRENGTH OF THE AGAR.

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
Do not remelt the solid agar, it will destroy the gel. The surface of the agar is soft but suitable for poured inocula.

Cultivate and isolate fastidious microorganisms and determine their hemolytic reactions using Thermo Scientific™ Oxoid™ Tryptose Blood Agar Base (Dehydrated) with supplementation of blood. This highly nutritious medium is specially developed by Casman for the preparation of a blood agar which will support the growth of many fastidious organisms.

The original formulation included 0.3g dextrose per litre which interfered with the hemolytic reactions. It is now used without dextrose as a standard medium.

Tryptose Blood Agar Base (Dehydrated), Oxoid Composition

Tryptose Blood Agar Preparation:
Suspend 30g in 1 litre of distilled water. Bring to the boil to dissolve completely. Sterilise by autoclaving at 121°C for 15 minutes.

For blood agar, cool the basal medium to 45-50°C and add 7% of sterile blood. Mix thoroughly, taking care to avoid incorporation of air bubbles, and dispense into Petri dishes or other containers.

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.

An improved medium, based on the Hynes modification of Leifsons medium for the isolation of Salmonellae and Shigellae. The improvement gives larger and more numerous colonies of Shigella species which can easily be picked off and emulsified in saline for slide agglutination tests.

Desoxycholate Citrate Agar (Hynes), Oxoid Composition

Desoxycholate Citrate Agar (Hynes), Oxoid Preparation:
Suspend 52g in 1 litre of distilled water. Bring to the boil over gauze and flame, to dissolve completely. Agitate to prevent charring. Cool to approximately 50°C and pour into sterile Petri dishes. Dry the agar surface before use.
THIS MEDIUM IS HEAT SENSITIVE: AVOID EXCESSIVE OR PROLONGED HEATING DURING RECONSTITUTION. DO NOT AUTOCLAVE OR REMELT.

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
The medium is best used freshly prepared.
Stock cultures of Shigella species may become predominantly in the R-phase when subcultured away from DCA media. Such cultures are difficult to use for control purposes without first heavily streaking the cultures on DCA plates and picking off the few S-phase colonies i.e. the macro-colonies on the agar surface, for further subculture.
When making biochemical tests on colonies picked from the surface of DCA plates, purity subcultures should be carried out because the colony may be contaminated with Escherichia coli present as micro-colonies.

A simple medium originally described by Crossley for the routine examination of canned food samples for anaerobic bacteria, this medium has evolved as the result of comparative trials carried out by Crossley with several standard media. It is capable of giving rapid growth without the use of special anaerobic apparatus, yet the bacteria detected may be provisionally identified by their reactions upon the medium.

Crossley milk medium, Oxoid Composition

Crossley milk medium, Oxoid Preparation:
Cream 110g of the powder with a little distilled water and gradually dilute to 1 litre with continuous mixing. Tube in 10ml quantities and autoclave at 121°C for 5 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.

Enumerate and differentiate bacteria in dairy products with this standard Thermo Scientific™ Oxoid™ China Blue Lactose Agar (Dehydrated). China Blue Lactose Agar, originally formulated by Brandl and Sobeck-skal, is a standard non-inhibitory solid medium used for the differentiation of lactose fermenters from non-lactose fermenters in milk.

The china blue in the medium serves as a pH indicator to differentiate lactose fermenters from non-lactose fermenters. The medium does not contain any inhibitory substances therefore all the organisms present in milk sample grow luxuriantly on this medium.

China Blue Lactose Agar Base, Oxoid Composition

China Blue Lactose Agar, Oxoid Preparation:
Suspend 35g in 1 litre of distilled water. Boil to dissolve completely. 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.

Precautions
It is important to remember that Gram positive and negative cocci and bacilli can grow on this medium. Always confirm the organism morphology and Gram reaction.

Isolate Salmonella typhi and other salmonllae from pathological material, sewage water supplies, food and other products with Thermo Scientific™ Oxoid™ Bismuth Sulphite Agar (Modified Wilson & Blair Medium) (Dehydrated). Bismuth Sulphite Agar is a modification of the original Wilson and Blair Medium and is particularly useful for the isolation of lactose-fermenting salmonellae. The presence of bismuth sulphite and brilliant green make this medium highly selective for salmonellae.

Bismuth Sulphite Agar, Oxoid Composition

Bismuth Sulphite Agar, Oxoid Preparation:
Suspend 20g in 500ml of distilled water in a 1 litre flask. Heat gently with frequent agitation until the medium just begins to boil and simmer for 30 seconds to dissolve the agar. Cool to 50-55°C, mix well to disperse suspension and pour thick plates (25 ml medium per plate). Allow the medium to solidify with the dish uncovered. Larger volumes may be prepared if great care is taken and adequate head space provided.
Dry the plates before use but take care to avoid overdrying. Correctly prepared plates should have a smooth, cream-like opacity with a pale straw colour. There should be no sedimentation of the indicator.
DO NOT OVERHEAT – DO NOT AUTOCLAVE

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label. Note the following comments:
Due to its contents of reactive and hygroscopic substances, dehydrated Bismuth Sulphite Agar quickly deteriorates when exposed to the atmosphere. This is usually indicated by aggregation into a solid non-friable mass, and by the development of a brown coloration. Medium reconstituted from such material is brown, does not become green on storage, and is characterised by loss of differential and selective properties. For this reason the powder should be stored in a cool, dry place and after use the container should be properly closed.

Precautions
Prepared plates of medium should not be stored for longer than two days at 2-8°C; after which time the dye oxidises to give a green medium that can be inhibitory to some salmonellae.

Shigella species are usually completely inhibited.

Salmonella sendai, Salmonella cholera-suis, Salmonella berta, Salmonella gallinarum and Salmonella abortus-equi are markedly inhibited.
It is important that the spreading technique yields well separated colonies. The typical colonial characteristics will not develop if the growth is too heavy or confluent; Salmonella typhi colonies will appear light green in these circumstances. Therefore, when in doubt, almost any growth on the medium should be subject to further tests.

Isolate and enumerate wild yeasts encountered in brewing while suppressing pitching yeasts with Thermo Scientific™ Oxoid™ Lysine Medium (Dehydrated). This complex, synthetic medium is based on the original formula of Morris & Eddy which utilizes the susceptibility of pitching yeasts to lysine to differentiate it from the wild yeast.

Lysine Medium, Oxoid Composition

Lysine Medium, Oxoid Preparation:
Suspend 6.6g in 100ml distilled water containing 1.0ml Potassium lactate SR0037. Bring to the boil to dissolve completely. Agitate frequently to prevent superheating. Cool to 50°C and add 0.1ml of lactic acid 10% SR0021 to adjust to pH 4.8 ± 0.2. Dispense into Petri dishes and remove surface moisture by drying at 37°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.

Oxoid Todd-Hewitt Broth is used for cultivation of Streptococci prior to serological grouping.

Todd-Hewitt Broth, Oxoid Composition

Todd-Hewitt Broth, Oxoid Preparation:
Dissolve 36.4 g in 1 litre of distilled water. Mix well, distribute into containers and sterilise by autoclaving at 115°C for 10 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.

Precautions
Streptococcus species grown in Todd-Hewitt Broth and harvested as antigens to raise antibodies, will sometimes carry antigenic material from the broth. This problem must be looked for in the antisera. If detected it would be preferable to use another medium to grow the test streptococci.

Cultivate aerobic and anaerobic organisms in the performance of sterility tests with Thermo Scientific™ Oxoid™ Thioglycollate Medium (USP) (Dehydrated). The medium is prepared according to the formula specified in the US Pharmacopoeia for the performance of sterility tests, and conforms to formulations detailed in the British and European Pharmacopoeia.

Thioglycollate Medium (USP) (Dehydrated), Oxoid Composition

Thioglycollate Medium (USP) (Dehydrated), Oxoid Preparation:
Suspend 29.75 g in 1 litre of distilled water. Bring to the boil to dissolve completely. Distribute into final containers, sterilise by autoclaving at 121°C for 15 minutes. Mix well and cool to room temperature.

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 away from light at room temperature.

Precautions
If the upper portion of the medium is red because of oxidation, anaerobic conditions can be restored by reheating for 10 minutes in boiling water or steam. Do not reheat more than once.
Following reheating, if more than one-third of the medium is oxidised then it should be discarded.
Some glucose-fermenting organisms which are able to reduce the pH of the medium to a critical level may not survive in this medium. Early subculture is necessary to isolate these organisms.