2-8°C

//2-8°C
  • A basic general-purpose blood free medium, capable of supporting the growth of most micro-organisms, including many fastidious organisms that do not require blood.
  • A general purpose medium enriched with 5% Defibrinated Horse Blood, suitable for the isolation of most organisms including many fastidious anaerobes.
  • Columbia Agar Base with 5% Horse Blood & Streptococcal Selective Supplement This is a medium for the selective isolation of Streptococcus spp. from clinical samples. Based on Columbia Agar Base enriched with 5% Horse Blood it is made selective by the addition of Colistin and Oxolinic Acid.
  • A very nutritious general-purpose medium based on Columbia Agar Base enriched with 5% Sheep Blood, suitable for the isolation of most organisms including most fastidious anaerobes of clinical significance. Many workers claim that β-haemolysis is more readily apparent, particularly in group A streptococci, when Sheep Blood is used in place of Horse Blood.
  • This is a medium for the selective isolation of Staphylococcus spp. and Streptococcus spp. primarily from clinical specimens. Based on Columbia Agar Base enriched with 7% Horse Blood the medium is made selective by the inclusion of Colistin and Nalidixic Acid to suppress the growth of the majority of Gram negative bacteria.
  • Columbia Agar Base with 7% Horse Blood & Gardnerella Supplement This is selective medium for the isolation of Gardnerella vaginalis from clinical samples. Based on Columbia Agar the medium is enriched with 7% Horse Blood and made selective by the addition of Colistin and Nalidixic Acid to suppress other bacteria
  • Columbia Agar Base with 7% Horse Blood & 50mg/L Neomycin Based on Columbia Agar enriched with 7% Horse Blood this formulation has been modified to include Neomycin, which will inhibit most gram-positive and gram-negative aerobes, making it suitable for use as a selective medium for the isolation of many anaerobes.
  • A very nutritious general-purpose medium based on Columbia Agar Base enriched with 7% Horse Blood, suitable for the cultivation and maintenance of most organisms including many fastidious anaerobes of clinical significance.
  • A very nutritious general-purpose medium based on Columbia Agar Base enriched with 7% Sheep Blood, suitable for the isolation of most organisms including most fastidious anaerobes of clinical significance. Many workers claim that β haemolysis is more readily apparent, particularly in group A streptococci, when Sheep Blood is used in place of Horse Blood.
  • This is a selective medium for the isolation of Staphylococcus and Streptococcus spp. Based on Columbia Agar, it is enriched by the addition of Sheep Blood (7%) the medium is also made selective by the inclusion of Colistin and Naladixic Acid to suppress the growth of the majority of Gram negative bacteria. The addition of sheep blood the medium allows for good colonial appearance, pigment production and excellent haemolysis from beta-haemolytic streptococci.
  • Columbia Blood Agar with 5% Defibrinated Horse Blood & Cap Selective Supplement This is a medium for the selective isolation of Staphylococcus spp. and Streptococcus spp. primarily from clinical specimens. Based on Columbia Agar Base enriched with 5% Horse Blood the medium is made selective by the inclusion of Colistin and Aztreonam to suppress the growth of the majority of Gram negative bacteria.
  • Side 1: Columbia Agar with 5% Horse Blood This is a general-purpose medium enriched with 5% defibrinated horse blood that is suitable for the isolation of most organisms, including many fastidious anaerobes. Side 2: Columbia Agar with 5% Horse Blood and CAP Selective Supplement This is a medium for the selective isolation of Staphylococcus spp. and Streptococcus  spp. primarily from clinical specimens. Based on Columbia Agar Base enriched with 5% horse blood the medium is made selective by the inclusion of colistin and aztreonam to suppress the growth of the majority of Gram-negative bacteria.
  • Side 1 – Columbia Agar w 5% Horse Blood This is a general-purpose medium with 5% defibrinated horse blood suitable for isolation of most organisms including fastidious anaerobes. Side 2- Chocolate Agar w 5% Horse Blood This is a highly nutritious medium supplemented with defibrinated horse blood and chocolated by heating to 70°C for 5 minutes. It will support the growth of a wide range of pathogens including the most fastidious organisms and is particularly useful for the cultivation of Haemophilus spp. and Neisseria spp
  • Side 1: Columbia Blood Agar with 7% Sheep Blood & CNA Supplement This is a selective medium for the isolation of Staphylococcus and Streptococcus spp. Based on columbia agar, it is enriched by the addition of sheep blood (7%) the medium is also made selective by the inclusion of colistin and nalidixic acid to suppress the growth of the majority of Gram negative bacteria. The addition of sheep blood to the medium allows for good colonial appearance, pigment production and excellent haemolysis from beta-haemolytic streptococci. Side 2: Sabouraud Dextrose Agar with Chloramphenicol A selective medium for the isolation of yeasts and fungi. Sabouraud dextrose agar is suitable for use in all areas of Mycology. The low pH of the medium inhibits most bacteria, however in this formulation chloramphenicol (150mg/L) is added to further reduce the risk when processing material that may be heavily contaminated particularly with coliforms.
  • A highly nutritious medium enriched with Horse Blood, where the blood has been ‘chocolated’ by heating the medium to 60°C. Suitable for the cultivation of most pathogens including many fastidious organisms and is particularly suitable for Haemophilus and Neisseria spp.
  • This is a selective medium for the cultivation of Taylorella equigenitalis or the contagious equine metritis organism (CEMO) that is the etiological agent for contagious equine metritis. Enzymatic digest of casein and soy peptone provide the required nitrogen, carbon and vitamins, and sodium chloride maintains the osmotic balance of the medium. Sodium sulphite is a reducing agent and L-cystine is an essential amino acid. In addition to this, the medium is further enriched by the inclusion of 7% chocolated horse blood. Amphotericin B is added to suppress the growth of contaminating fungi and yeasts and both clindamycin and trimethoprim are added to suppress bacterial contaminants.
  • This is a selective medium for the cultivation of Taylorella equigenitalis or the contagious equine metritis organism (CEMO) that is the etiological agent for contagious equine metritis. Enzymatic digest of casein and soy peptone provide the required nitrogen, carbon and vitamins, and sodium chloride maintains the osmotic balance of the medium. Sodium sulphite is a reducing agent and L-cystine is an essential amino acid. In addition to this, the medium is further enriched by the inclusion of 7% chocolated horse blood. Amphotericin B is added to suppress the growth of contaminating fungi and yeasts.
  • This is a selective medium for the cultivation of Taylorella equigenitalis or the contagious equine metritis organism (CEMO) that is the etiological agent for contagious equine metritis. Enzymatic digest of casein and soy peptone provide the required nitrogen, carbon and vitamins, and sodium chloride maintains the osmotic balance of the medium. Sodium sulphite is a reducing agent and L-cystine is an essential amino acid. In addition to this, the medium is further enriched by the inclusion of 7% chocolated horse blood. Amphotericin B and streptomycin are added to suppress the growth of fungal/yeast and bacterial contaminants, respectively.
  • It is not possible to sterilise whole blood products and therefore they must be collected aseptically. Horse and sheep blood are the most widely used animal blood products in culture media. The choice of  which type of blood to use with culture media is largely traditional, with much of continental Europe preferring sheep blood, whilst the UK and certain parts of the Commonwealth  prefer horse blood. Defibrinated horse blood is aseptically collected whole horse blood that has been processed to remove fibrin. There are no additives or preservatives in this product. Defibrination is now accepted as the best method of preventing blood clotting. It must be carried out immediately after drawing the blood and the agitation must be sufficient to denature the fibrinogen but not to cause rupture of the erythrocytes and haemolysis. The haemolytic reactions of horse blood are not identical to sheep blood and blood agar media designed for horse blood may not be satisfactory with sheep blood and vice versa.
  • It is not possible to sterilise whole blood products and therefore they must be collected aseptically. Horse and sheep blood are the most widely used animal blood products in culture media. The choice of  which type of blood to use with culture media is largely traditional, with much of continental Europe preferring sheep blood, whilst the UK and  certain parts of the Commonwealth  prefer horse blood. Defibrinated sheep cells are aseptically collected whole sheep blood that has been processed to remove fibrin. There are no additives or preservatives in this product. Defibrination is now accepted as the best method of preventing blood clotting. It must be carried out immediately after drawing the blood and the agitation must be sufficient to denature the fibrinogen but not to cause rupture of the erythrocytes and haemolysis. The haemolytic reactions of sheep blood are not identical to the reactions of horse blood and blood agar media designed for sheep blood may not be satisfactory with horse blood and vice versa.
  • Dermatophyte Test Medium with Chloramphenicol & Cyclohexamide (Actidione) This is a selective medium for the isolation of dermatophytes that includes a Phenol Red indicator to assist in the differentiation between dermatophytes and other pathogenic fungi. Although the low pH (5.5) of the medium inhibits most bacteria, Chloramphenicol is added to further reduce the risk when processing material that may be more heavily contaminated. Cyclohexamide (Actidione) is also added to suppress the growth of most yeasts and saprophytic fungi. Dermatophytes appear as fluffy white colonies and produce a red colour on the medium while other fungi cause the medium to become yellow due to acid production. Yeasts will also grow on this medium but are readily distinguished by their distinct white/creamy colonies and distinctive smell. NB: Prolonged incubation should be avoided as this may cause fungi other than dermatophytes to turn the medium red
  • Desoxycholate Citrate Agar (DCA) (Hynes) One of several media designed for the differential selective isolation of Salmonella and Shigella spp from clinical and environmental samples. Lactose is added to the medium together with Neutral Red indicator to assist in the differentiation of Lactose and Non-Lactose fermenting organisms. The medium is made selective by the inclusion of Sodium Desoxycholate and Sodium Thiosulphate, which will inhibit most gram-positive organisms. The Sodium Thiosulphate is also broken down by the enzyme thiosulphate reductase to form Sodium Sulphite and Hydrogen Sulphide. The Hydrogen Sulphide, if present, will in turn react with the ferric ions to produce a black precipitate of Ferrous Sulphide and give rise to the classical black centre of most Salmonellae. It has been suggested that this medium may be more suitable for secondary post-enrichment isolation while the original formulation is more appropriate for the primary inoculation of samples.
  • Dichloran Rose-Bengal Chloramphenicol (DRBC) Agar Dichloran Rose Bengal Chloramphenicol Agar is based on the formulation described by King et al. It is a selective medium for the isolation and enumeration of yeasts and mould that are of significance in food spoilage. The medium is a modification to Rose Bengal Chloramphenicol Agar and is recommended by the International Standard ISO 21527:2008 part 1.
  • PP0400

    DNase Agar

    DN'ase Medium DNase Agar is used primarily in clinical laboratories to differentiate Staphylococcus aureus from other Staphylococci based on deoxyribonuclease activity. Following incubation of the plate and confirmation of a pure growth of Staphylococci, the surface of the medium is covered with a small quantity of 1M Hydrochloric Acid to precipitate the DNA. Staphylococcus aureus produce DNase enzymes that hydrolyse DNA resulting in a clear area around the colonies, described as being DNase positive, whereas coagulase negative Staphylococci do not produce clearing. NB: As with most tests of this type a positive result should not be taken in isolation and other appropriate tests, e.g. Coagulase Test, Latex Agglutination etc, should be carried out.
  • DNase Agar is used primarily in clinical laboratories to differentiate Staphylococcus aureus from other staphylococci based on deoxyribonuclease activity. Staphylococcus aureus produce DNase enzymes that hydrolyse DNA resulting in a colourless zone around the colonies, described as being DNase positive, whereas coagulase negative staphylococci do not produce clearing. This particular formulation can also be used for Streptococci and Serratia. NB: As with most tests of this type a positive result should not be taken in isolation and other appropriate tests, e.g. Coagulase Test, Latex Agglutination etc, should be carried out.
  • Edwards Medium (Modified) with 7% Sheep Blood This is a medium for the selective isolation of streptococci, particularly Streptococcus agalactiae, involved in bovine mastitis. The medium is enriched by the addition of 7% Sheep Blood and made selective by the inclusion of Crystal Violet and Thallous Sulphate. Aesculin is also present and assists in the differentiation of Streptococcus agalactiae, which give rise to blue colonies, from Aesculin positive Group D streptococci which produce black colonies.
  • A sterile concentrated emulsion of premium egg yolks, suitable for incorporation in culture media which detect lecithinase production by bacteria. It can be used in media for Bacillus cereus and Staphylococci. Used with serum and Filde’s extract it may be used to produce Nagler plates for Clostridia.
  • This is a sterile emulsion of Egg Yolk in Saline containing Potassium Tellurite and is generally used as a selective differential agent in Baird Parker Medium. The complete medium is selective for Staphylococcus aureus as the Potassium Tellurite inhibits most coliform organisms and is also reduced by Staphylococcus aureus to tellurite giving typical black colonies on the Baird Parker Medium.
  • Escherichia coli 0157 Selective Supplement E&O Laboratories Ltd Escherichia coli 0157 Selective Supplement (LS0013) is an antibiotic supplement used to enhance the isolation of Escherichia coli serogroup O157 from faecal, food and environmental specimens.  
  • Fastidious Anaerobe Agar is intended as a primary isolation medium capable of supporting most clinically significant anaerobes including fastidious organisms. The formulation is complex and includes detoxification agents (Starch & Sodium Bicarbonate), growth enhancing agents (Cysteine, Arginine, Vitamin K, Sodium Succinate, Glucose and pyrophosphate) as well as Haemin to encourage pigment production in Porphyromonas melaninogenicus. Sodium Pyruvate is also included to help neutralise Hydrogen Peroxide. One side of the bi-plate consists of standard FAA supplemented with 7% horse blood; the other side is FAA with horse blood and Neomycin (75mg/L) for the selective isolation of target organisms.
  • Fastidious Anaerobe Agar (FAA) with 5% Sheep Blood Fastidious Anaerobe Agar is intended as a primary isolation medium capable of supporting most clinically significant anaerobes including fastidious organisms. The formulation is complex and includes detoxification agents (Starch & Sodium Bicarbonate) growth enhancing agents (Cysteine, Arginine, Vitamin K, Sodium Succinate, Glucose and pyrophosphate) as well as Haemin to encourage pigment production in Porphyromonas melaninogenicus. Sodium Pyruvate is also included to help neutralise Hydrogen Peroxide. In this instance the medium is further enriched by the addition of 5% Sheep Blood.
  • Fastidious Anaerobe Agar is intended as a primary isolation medium capable of supporting most clinically significant anaerobes including fastidious organisms. The formulation is complex and includes detoxification agents (starch and sodium bicarbonate), growth enhancing agents (cysteine, arginine, vitamin K, sodium succinate, glucose and pyrophosphate), as well as haemin to encourage pigment production in Porphyromonas melaninogenicus. Sodium pyruvate is also included to help neutralise hydrogen peroxide. In this instance the medium is further enriched by the addition of 5% horse blood. This product is suitable for use with the EUCAST disc diffusion method for selected rapidly growing anaerobic bacteria.
  • Fastidious Anaerobe Agar with 7% Horse Blood Fastidious Anaerobe Agar is intended as a primary isolation medium capable of supporting most clinically significant anaerobes including fastidious organisms. The formulation is complex and includes detoxification agents (Starch & Sodium Bicarbonate) growth enhancing agents (Cysteine, Arginine, Vitamin K, Sodium Succinate, Glucose and pyrophosphate) as well as Haemin to encourage pigment production in Porphyromonas melaninogenicus. Sodium Pyruvate is also included to help neutralise Hydrogen Peroxide. In this instance the medium is further enriched by the addition of 7% Horse Blood.
  • Fastidious Anaerobe Agar (FAA) with 7% Horse Blood & Neomycin (75mg/L) Fastidious Anaerobe Agar is intended as a primary isolation medium capable of supporting most clinically significant anaerobes including fastidious organisms. The formulation is complex and includes detoxification agents (Starch & Sodium Bicarbonate) as well as growth enhancing agents (Cysteine, Arginine, Vitamin K, Sodium Succinate, Glucose and pyrophosphate) as well as Haemin to encourage pigment production in Porphyromonas melaninogenicus. Sodium Pyruvate is also included to help neutralise Hydrogen Peroxide. In this instance the medium is made more selective by the inclusion of 75mg/L of Neomycin to inhibit most enteric organisms and further enriched by the addition of 7% Horse Blood.
  • Fastidious Anaerobe Agar with 7% Horse Blood, Vancomycin (6mg/L) & Nalidixic Acid (10mg/L) This is a selective medium for the isolation of gram-negative anaerobes from clinical specimens. The base medium, Fastidious Anaerobe Agar, is complex and includes detoxification agents (Starch & Sodium Bicarbonate), growth enhancing agents (Cysteine, Arginine, Vitamin K, Sodium Succinate, Glucose and pyrophosphate) as well as Haemin to encourage pigment production where appropriate. Sodium Pyruvate is also included to help neutralise Hydrogen Peroxide. The medium is made selective, by the inclusion of Naladixic Acid and Vancomycin and further enriched by the addition of 7% Horse Blood.
  • This is a selective medium for the isolation of clinically significant anaerobes including fastidious organisms. The formulation is complex and includes detoxification agents (starch and sodium hydrogen carbonate), growth enhancing agents (cysteine, arginine, menadione, sodium succinate, glucose and pyrophosphate) and haemin to encourage pigment production in Porphyromonas melaninogenicus. Sodium pyruvate is included to help neutralise hydrogen peroxide. The medium is made selective by the inclusion of nalidixic acid and further enriched by the addition of 7% defibrinated horse blood. Tween 80 is added to encourage the growth of anaerobic streptococci.
  • Fastidious Anaerobe Agar is intended as a primary isolation medium capable of supporting most clinically significant anaerobes including fastidious organisms. The formulation is complex and includes detoxification agents (starch & sodium bicarbonate) as well as growth enhancing agents (cysteine, arginine, vitamin K, sodium succinate, glucose and pyrophosphate) as well as haemin to encourage pigment production in Porphyromonas melaninogenicus . Sodium pyruvate is also included to help neutralise hydrogen peroxide. In this instance the medium is made more selective by the inclusion of neomycin and aztreonam to inhibit most enteric organisms and further enriched by the addition of 7% horse blood.
  • Ferric Ammonium Citrate (FAC) Supplement E&O Laboratories Ltd Ferric Ammonium Citrate (LS5004) is a supplement used in the isolation of Listeria spp. with Fraser Broth. Fraser Broth is a modification of the USDA-FSIS (United States Department of Agriculture-Food Safety Inspection Service) UVM secondary enrichment broth and is based on the formula described by Fraser and Sperber. Blackening of the medium is presumptive evidence of the presence of Listeria. Contrary to early indications, cultures which do not blacken cannot be assumed to be Listeria-free. All Fraser Broth enrichment cultures should be subcultured to plating medium. The medium is intended for the isolation of Listeria spp. from food and environmental samples when used as the secondary enrichment medium in the USDA-FSIS methodology for Listeria isolation. It is generally accepted that the USDA-FSIS two stage enrichment method employing UVM primary and secondary enrichment broths is the most suitable for the examination of meat products.
  • BM0640

    Fraser Broth

    A modification of UVM Medium, Fraser Broth is a secondary selective enrichment broth for the isolation of Listeria spp primarily from food and environmental specimens. The medium is made selective by the inclusion of Nalidixic Acid and Acriflavine. Darkening of the broth following incubation, due to the presence of Aesculin and Ferric Ammonium Citrate, is indicative of the presence of Listeria spp. Lithium Chloride is also included to inhibit the growth of enterococci that would otherwise hydrolyse the Aesculin. This medium is generally used in conjunction with Fraser Broth Half-Strength (BM0647). NB:  It should be noted that the lack of darkening of the broth should not be taken as a final negative result and all Fraser Broth enrichment cultures should be sub-cultured onto an appropriate selective agar medium irrespective of colour.
  • A modification of UVM11 Medium, Fraser Broth Half-Strength is a primary selective enrichment broth for the isolation of Listeria spp. from food and environmental samples and is generally used in conjunction with Fraser Broth (BM0640). Although the base is identical to Fraser Broth it differs in that it contains only half the quantity of selective agents (Nalidixic acid and Acriflavine).
  • Fraser Broth Selective Supplement E&O Laboratories Ltd Fraser Broth Selective Supplement (LS5002) is an antibiotic supplement used to enhance the selective isolation of Listeria spp. in combination with Fraser Broth.  
  • Vancomycin. Colistin, Amphotericin, Trimehtoprim (V.C.A.T) E&O Laboratories Ltd VCAT Selective Supplement (LS0002) is an antibiotic supplement used to enhance the selective isolation of Neisseria gonorrhoeae and Neisseria meningitidis.  
  • This is a non-selective medium for the maintenance of Neisseria gonorrhoeae cultures. Based on the medium developed by Thayer & Martin, it includes Corn Starch to absorb toxic metabolites and is buffered to maintain a neutral pH. Yeast Extract and Glucose are also added as further enrichment along with laked horse blood to ensure an more luxuriant growth of Neisseria gonorrhoeae. NB: This is a Basic medium only and DOES NOT contain any selective agents. It is therefore not recommended for use as a primary isolation medium.
  • This is one of a number of media available for the selective isolation of Neisseria gonorrhoeae. Based on the medium of Thayer & Martin it includes Corn Starch to absorb toxic metabolites and is buffered to maintain a neutral pH. The medium is enriched with Defibrinated Horse Blood where the blood has been ‘chocolated’ by heating the medium to 60°C and made selective by the inclusion of VCAT (Vancomycin, Colistin, Amphotericin and Trimethoprim). Vancomycin and Colistin inhibit the growth of the majority of contaminating organisms likely to be present. Trimethoprim is included to reduce the spread of Proteus spp and Amphotericin to suppress yeasts. Yeast Extract and Glucose are also added as further enrichment.
  • GC LCAT Selective Supplement E&O Laboratories Ltd LCAT Selective Supplement (LS0001) is an antibiotic supplement used to enhance the selective isolation of Neisseria gonorrhoeae and Neisseria meningitidis.  
  • There are a number of media available for the selective isolation of Neisseria gonorrhoeae of which this is one. Based on the medium developed by Thayer & Martin, it includes Corn Starch to absorb toxic metabolites and is buffered to maintain a neutral pH. The medium is made selective by the inclusion of LCAT (Lincomycin, Colistin, Amphotericin B & Trimethoprim). Lincomycin and Colistin inhibit the growth of the majority of contaminating organisms likely to be present. Trimethoprim is included to reduce the spreading of Proteus spp and Amphotericin B to inhibit yeasts and fungi. Yeast Extract and Glucose are also added as further enrichment along with laked horse blood to ensure an more luxuriant growth of Neisseria gonorrhoeae.
  • There are a number of media available for the selective isolation of Neisseria gonorrhoeae of which this is one. Based on the medium developed by Thayer & Martin, it includes Corn Starch to absorb toxic metabolites and is buffered to maintain a neutral pH. The medium is made selective by the inclusion of VCAT (Vancomycin, Colistin, Amphotericin B & Trimethoprim). Vancomycin and Colistin inhibit the growth of the majority of contaminating organisms likely to be present. Trimethoprim is included to reduce the spreading of Proteus spp and Amphotericin B to inhibit yeasts and fungi. Yeast Extract and Glucose are also added as further enrichment along with laked horse blood to ensure an more luxuriant growth of Neisseria gonorrhoeae.
  • There are a number of media available for the selective isolation of Neisseria gonorrhoeae of which this is one. Based on the medium developed by Thayer & Martin, it includes Corn Starch to absorb toxic metabolites and is buffered to maintain a neutral pH. The medium is made selective by the inclusion of VCNT (Vancomycin, Colistin, Nystatin & Trimethoprim). Vancomycin and Colistin inhibit the growth of the majority of contaminating organisms likely to be present. Trimethoprim is included to reduce the spreading of Proteus spp and Nystatin to inhibit yeasts and fungi. Yeast Extract and Glucose are also added as further enrichment along with laked horse blood to ensure an more luxuriant growth of Neisseria gonorrhoeae.
  • A medium for the selective isolation of group B streptococci. This information has been obtained directly from the HPA files at the customers request.
  • Half Fraser Broth Selective Supplement E&O Laboratories Ltd Half Fraser Selective Supplement (LS5003) is selective supplement for the primary enrichment of Listeria spp from food and environmental samples when used with Fraser Broth.Fraser Broth is a modification of the USDA-FSIS (United States Department of Agriculture-Food Safety Inspection Service) UVM secondary enrichment broth and is based on the formula described by Fraser and Sperber. It contains ferric ammonium citrate and lithium chloride. Blackening of the medium is presumptive evidence of the presence of Listeria. Contrary to early indications, cultures which do not blacken cannot be assumed to be Listeria-free. All Fraser Broth enrichment cultures should be subcultured to plating medium. Fraser Broth has proven to be remarkably accurate in detecting Listeria spp. in food and environmental samples. All Listeria spp. hydrolyse aesculin to aesculetin. Aesculetin reacts with ferric ions which results in blackening. Another possible advantage to the addition of ferric ammonium citrate is that it has been shown that ferric ions enhance the growth of Listeria monocytogenes. Lithium chloride is included in the medium to inhibit the growth of enterococci which can also hydrolyse aesculin. Half Fraser Broth is a modification of Fraser Broth which contains half of the concentration of nalidixic acid and acriflavine hydrochloride to aid in the recovery of stressed cells. Half Fraser Broth is used as the primary enrichment broth in the ISO methodology for the detection of Listeria.