Microbiology

Grow and isolate aerobic and anaerobic organisms of the intestinal tract, which may require selective conditions to inhibit the growth of background organisms like Escherichia coli, with Thermo Scientific™ Oxoid™ Schaedler Anaerobe Agar. The presence of cysteine in the medium provides selectivity against Escherichia coli as cysteine has shown to have inhibitory effects on several enzymatic reactions of Escherichia coli in vitro.¹

Schaedler Anaerobe Agar, Oxoid Composition

Schaedler Anaerobe Agar, Oxoid Preparation:
Suspend 40g in 1 litre of distilled water and boil to dissolve the medium 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°C and use before the expiry date on the label.
Prepared plates may be stored at 2-8°C if suitably protected.

Isolate and differentiate Shigella and Salmonella spp. from enteric pathological specimens with Thermo Scientific™ Oxoid™ Hektoen Enteric Agar (Dehydrated). Hektoen Enteric Agar was developed by King and Metzger. When compared to other selective media this medium gives higher yield of Salmonella and Shigella, while inhibiting accompanying Gram-positive and other microorganisms.

Hektoen Enteric Agar, Oxoid Composition

Hektoen Enteric Agar, Oxoid Preparation:
Suspend 76g of the medium in 1 litre of distilled water and soak for 10 minutes. Heat gently and allow to boil for a few seconds to dissolve the agar. DO NOT AUTOCLAVE. Cool to 50°C 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 at 2-8°C.

Precautions
Do not overheat the medium or hold it molten for long periods. Proteus species may resemble salmonellae or shigellae.
Further testing must be carried out to confirm the presumptive identification of organisms isolated on this medium.

A medium specially designed to give large, clear zones with all antibiotics, without the addition of lysed or whole blood.

Sensitest Agar, Oxoid Composition

Sensitest Agar, Oxoid Preparation:
Suspend 32g 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 plates of agar at 2-8°C.

Precautions
As with other susceptibility testing media, Sensitest Agar should be used for rapidly growing aerobic organisms only. It should not be modified by the addition of carbohydrates or incubated in a CO2 enriched atmosphere.
If the medium is used for Bell’s CDS method then the specified discs and technique must be used. Refer to the monograph cited in the References.

Mueller Hinton Broth, Oxoid conforms to international standards for antimicrobial susceptibility testing media.

Mueller Hinton Broth, Oxoid Preparation
Place 21.0g of Mueller Hinton Broth, Oxoid in 1 litre of distilled water mix to dissolve completely. Sterilize by autoclaving at 121°C for 15 minutes. Chill and adjust cation levels if necessary.

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

Precautions
Monitor the performance of the broth routinely using the standard QC organisms. If the broth does not yield the expected MIC values, modify the volumes of Mg++ and Ca++ solutions.

If the thymidine content is lowered, after the addition of lysed horse blood or thymidine phosphorylase, the MIC values may be lower.

• Oxoid Mycoplasma Broth Base is used for the selective isolation of Mycoplasma species.
• Also available Mycoplasma Supplement G, Part No. SR0059C.

Mycoplasma Broth Base, Oxoid Composition

Mycoplasma Broth, Oxoid Preparation:
Dissolve 25.5g in 1 litre of distilled water. Mix well and distribute in 80ml volumes. Sterilise by autoclaving at 121°C for 15 minutes. Cool to approximately 50°C and add one vial of Mycoplasma Supplement SR0059 reconstituted as directed.

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
Thallous acetate is toxic, observe the precautions stated under Hazards section..
Sub-culture the broth to agar as soon as any indicator added begins to change colour before the pH change destroys the organism.

• Oxoid Mycoplasma Agar Base is used for the selective isolation of Mycoplasma pneumoniae.
• Also available Mycoplasma Supplement P, Part No. SR0060C and Mycoplasma Supplement G, Part No. SR0059C.

Mycoplasma Agar Base, Oxoid Composition

Mycoplasma Agar, Oxoid Preparation:
Add 35.5g to 1 litre of distilled water. Boil to dissolve the agar and distribute in 80ml volumes. Sterilise by autoclaving at 121°C for 15 minutes. Cool to approximately 50°C and add one vial of Mycoplasma Supplement SR0059 reconstituted as directed.

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
Thallous acetate is toxic, observe the precautions in the HAZARDS section.
Do not use thallous acetate media to isolate Ureaplasma urealyticum.
Mycoplasmas may be suspected if (1) typical morphology (2) no growth in media without serum (3) colonies are embedded below the agar surface.

Enrich and isolate Salmonella from feces and food products with Thermo Scientific™ Oxoid™ Selenite Broth Base (Lactose).The presence of Selenium in the medium provides selectivity against non-target bacteria.

Selenite Broth Base (Lactose), Oxoid Composition

Selenite Broth Base (Lactose), Oxoid Preparation:
Dissolve 4g of sodium biselenite LP0121 in 1 litre of distilled water and then add 19g of Selenite Broth Base. Warm to dissolve, mix well and fill out into containers. Sterilise in a boiling water bath, or in free flowing steam, for 10 minutes. DO NOT AUTOCLAVE.

To minimise any possible risk of teratogenicity to laboratory workers, the sodium biselenite must be added as a solution to this medium.
Robertson1 reported miscarriages and possible teratogenic effects on pregnant laboratory assistants which may have been caused by ingested sodium biselenite. Oxoid therefore removed this substance from the powdered medium.

Although no further reports have been received sodium biselenite is now considered to be very toxic and should be handled with great care.

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.

Precautions
Discard the prepared medium if large amounts of reduced selenite can be seen as a red precipitate in the bottom of the bottles.
Do not incubate longer than 24 hours because the inhibitory effect of selenite is reduced after 6-12 hours incubation.
Take sub-cultures of broth from the upper third of the broth column, which should be at least 5 cm in depth.

DCLS Agar is a modified form of Desoxycholate Citrate Agar which includes sucrose in its formulation. The addition of this fermentable carbohydrate increases the usefulness of the medium because non-pathogenic sucrose-fermenting organisms may be recognised by their red colonies, e.g. some Proteus, Enterobacter and Klebsiella species.

DCLS Agar, Oxoid Composition

DCLS Agar, Oxoid Preparation:
Suspend 50g in 1 litre of distilled water. Bring to the boil to dissolve the medium. Cool to 50°C and pour into sterile Petri dishes.
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 agar plates at 2-8°C.

Precautions
Boil the medium for the minimal period of time to get the agar into solution. Overheating reduces the agar gel strength and increases the degree of inhibition. It is therefore important not to hold the molten medium at 50°C for more than the short time required to distribute it into dishes.

Thioglycollate Medium USP – Alternative, is intended for sterility testing with certain biological products that are turbid or otherwise do not lend themselves readily to culturing in Thioglycollate Medium USP (CM0173) because of its viscosity.

Thioglycollate Medium USP – Alternative, Oxoid Composition

Thioglycollate Medium USP – Alternative, Oxoid Preparation:
Suspend 29g in 1 litre of distilled water. Bring to the boil and dissolve the medium completely. Distribute into tubes or bottles and sterilise by autoclaving at 121°C for 15 minutes.
PREPARE FRESHLY OR BOIL AND COOL THE MEDIUM JUST BEFORE USE.

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

Whilst storage of the prepared medium is not recommended, autoclaved volumes of Thioglycollate Medium USP – Alternative, should be held at 20-30°C in the dark. Storage at lower temperatures increases oxygen absorption.

Precautions
This medium lacks agar and reducing indicator, therefore it is essential that the medium is freshly prepared and used within four hours of preparation.
Thioglycollate media should not be reheated more than once because toxic oxygen radicles are formed on reheating.

Detect salmonellae including Salmonella arizonae with the diagnostic Thermo Scientific™ Oxoid™ Lysine Iron Agar (Dehydrated). This differential medium detects salmonellae (including lactose fermenting Salmonella arizonae) by lysine decarboxylase activity and H₂S production.

Lysine Iron Agar, Oxoid Composition

Lysine Iron Agar, Oxoid Preparation:
Suspend 34g in 1 litre of distilled water. Bring to the boil to dissolve completely. Dispense into tubes and sterilise by autoclaving at 121° C for 15 minutes. Cool the tubes in an inclined position to form slants with deep butts.

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 and enumerate enterococci from water and food samples with Thermo Scientific™ Slanetz and Bartley Medium (Dehydrated). Slanetz and Bartley originally devised this medium to detect and enumerate enterococci by the technique of membrane filtration, but it has also proved useful as a direct plating medium. The medium is very selective for enterococci and, when it is incubated at elevated temperatures (44-45°C), all red or maroon colonies may be accepted as presumptive enterococci.

Slanetz and Bartley Medium (Dehydrated), Oxoid Composition

Slanetz and Bartley Medium Preparation:
Suspend 42g in 1 litre of distilled water and bring to the boil to dissolve the agar completely.

EXCESSIVE HEATING MUST BE AVOIDED. Dispense into Petri dishes and allow to solidify. It should not be remelted. The medium may be used with membrane filters or by spreading dilutions of the sample over the surface of the agar with a glass rod.

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.

Precautions
Count all red, maroon or pink colonies as presumptive enterococci. Not all species reduce TTC therefore pale colonies should not be ignored.
Although incubation at 35°C yields a higher count, it allows the growth of organisms which do not conform to the definition of enterococci. Incubation at 44-45°C has a selective effect and produces fewer false-positives. However, the preliminary incubation at 35°C encourages the recovery of stressed organisms.
Although the selective properties of this medium are very good it is advisable to regard the colony count as a presumptive or unconfirmed count. Further identification may be required depending on the scope of the examination.

Selectively isolate Neisseria species with Thermo Scientific™ Oxoid™ GC Agar Base (Dehydrated). GC Agar Base has been formulated to include Special Peptone LP0072 which is a mixture of meat and plant enzymatic digests. The presence of starch in the medium ensures that toxic metabolites produced by Neisseria are absorbed. Phosphate buffers are included to prevent changes in pH due to amine production that would affect the survival of the organism

GC Agar Base, Oxoid Composition

Oxoid Muller-Kauffmann Tetrathionate Broth Base is selective enrichment medium for isolation of Salmonella spp. and suppression of Proteus species.

Muller-Kauffmann Tetrathionate Broth Base, Oxoid Composition

Muller-Kauffmann Tetrathionate Broth, Oxoid Preparation:
Suspend 82g in 1 litre of distilled water and bring to the boil. Cool below 45°C and add, just prior to use, 19ml of iodine solution and 9.5ml of a 0.1% brilliant green solution. Mix well and fill out into sterile tubes or flasks.

Dissolve the potassium iodide in approximately 5ml of distilled water, add the iodide and gently warm the solution to completely dissolve it. Make up the volume to 100ml with distilled water.

Add the brilliant green to the distilled water and shake to dissolve the dye. Heat the solution to 100°C for 30 minutes and shake from time to time whilst cooling, to ensure that the dye has completely dissolved. Store in a brown glass bottle or away from light.

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 autoclave the base broth.
Add the iodine solution and brilliant green just prior to use.
The medium is not suitable for the growth of Salmonella typhi, Salmonella sendai, Salmonella pullorum and Salmonella gallinarum.

Selectively isolate pathogenic Vibrio species with Thermo Scientific™ Oxoid™ TCBS (Thiosulfate Citrate Bile Salts Sucrose) Cholera Medium (Dehydrated). The medium has shown to be the most satisfactory and reproducible formula regardless of the complex composition. Unlike Lauryl Sulphate Tellurite Agar it does not require further additives or aseptic additions of blood. It also possesses superior growth characteristics for Vibrio species, compared with tellurite media. While inhibiting non-vibrios, it promotes rapid growth of pathogenic vibrios after overnight incubation at 35°C.

TCBS (Thiosulfate Citrate Bile Salts Sucrose) Cholera Medium (Dehydrated), Oxoid Composition

TCBS (Thiosulfate Citrate Bile Salts Sucrose) Cholera Medium (Dehydrated), Oxoid Preparation:
Suspend 88g in 1 litre of distilled water. Boil to dissolve the medium completely. DO NOT AUTOCLAVE.
Pour plates without further heating and dry before use.

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 identification of the various Vibrio species on TCBS Medium is presumptive and further tests are required for confirmation.
Yellow colonies on TCBS Medium will give unsatisfactory oxidase reactions.
Colonies taken from TCBS Medium are `sticky’ and react poorly in slide agglutination tests. Subculture to nutrient agar is required before slide agglutination tests can be carried out.
Some strains of Vibrio vulnificus produce better recovery at 30°C.

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.