This culture medium contains lactose, whose degradation to acid is indicated by the pH indicator phenol red, which changes its colour to yellow. The indicator exhibits a deep red colour in the alkaline range. The growth of the accompanying Gram-positive microbial flora, Salmonella typhi and Shigella is largely inhibited by brilliant green. The growth of Salmonella is, however, improved by the richer nutrient base. Increased growth of accompanying microorganisms is considerably prevented by raising the concentration of brilliant green. Salmonellae are not able to ferment either lactose or sucrose. Thus in contrast to BPL agar, the sucrose contained in this medium allows identification of accompanying, weakly lactose-positive or lactose-negative, but sucrose-positive microorganisms.

Principles and uses
Hektoen Enteric Agar is a differential and selective medium used for isolating and differentiating enteric pathogens such as Salmonella and Shigella, both of which cause a variety of serious human gastrointestinal diseases; and other Gram-negative Enterobacteriaceae.
It is used particularly in foods where multi-steps are followed to isolate the pathogens of gastroenteritis. The nutrients for growth are provided by the Meat Peptone and Yeast extract. The increased content of the Peptone and the three fermentable carbohydrates (Lactose, Sucrose, Salicin) as sources of carbon and energy reduce the inhibitory action of the Bile salts on Salmonella and Shigella spp. The lactose concentration in this medium is higher than in many other media used for enterics since this helps the visualization of enteric pathogens and minimizes the problem of delayed lactose fermentation. Bromothymol blue and Acid fuchsin are pH indicators. Sodium thiosulfate provides Sulphur, and Ferric ammonium citrate is the indicator for
H2S production. H2S positive colonies are black-centered. Sodium chloride maintains the osmotic balance.
The norma ISO 21567 recommends the Hektoen Agar as a selective solid media for the enumeration of Shigella spp. Although suppressed, partially inhibited E. coli and other organisms which use lactose, sucrose, and/or salicin with the production of acid, give colonies whose tones vary from yellow to orange to salmon. The Salmonella and Shigella are green or green-blue. Proteus is not inhibited but produces a green-yellow colony when it grows. The colonies of Proteus and Salmonella may present a black center and clear edges if they form iron sulfide as a result of H2S production.

Preparation
Suspend 75,6 grams of the medium in one liter of distilled water. Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. AVOID OVERHEATING. DO NOT AUTOCLAVE. Cool to 47 ºC and pour into Petri dishes.

This is a selective enrichment broth for the isolation of Salmonella spp. primarily from food and food product samples and conforms to the requirements ISO 6579:2002. It can however be used in other areas including clinical and environmental specimens. Salmonella spp. reduce tetrathionate and will proliferate in the medium whilst most other enteric organisms are inhibited. Unlike the older traditional tetrathionate broth the addition of novobiocin (40 mg/l) improves the inhibition of Proteus spp.
Immediately prior to use it is necessary to add 20 ml/l of 2% iodine/iodide solution Once the iodine/iodide solution has been added the medium should be used immediately and cannot be stored for future use.
NB: As this is an opaque medium, the turbidity of the broth alone cannot be used as an indication of growth.

Principles and uses
Muller-Kauffmann Broth Base with Brilliant Green and Novobiocin (MKTTN) is recommended by the ISO 6579 and ISO 19250 norms to be used as a selective enrichment broth for the detection of Salmonella spp in all food types, including milk and dairy products, molluscan shellfish and other fish products, and in water samples and environmental swabs.
Beef extract and casein peptone provide nitrogen, vitamins, minerals and amino acids essential for growth. Calcium carbonate is a neutralizer which absorbs toxic metabolites. Bile salts, brilliant green and novobiocin inhibit organisms other than Salmonella. Selectivity is also obtained by both sodium thiosulfate and tetrathionate, suppressing coliforms. Tetrathionate is formed in the medium with the addition of the iodine and potassium iodide solution.
Organisms containing the enzyme tetrathionate reductase will thrive in this medium. Sodium chloride supplies essential electrolytes for transport and osmotic balance.

Preparation
Suspend 89,53 grams of the medium in one litre of distilled water. Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. AVOID OVERHEATING. DO NOT AUTOCLAVE. Cool to 45-50ºC. Aseptically Add 20 ml of an iodine and potassium iodide
solution (20 g of iodine and 25 g of potassium iodide in 100 ml of sterile distilled water). Homogenize gently and dispense into sterile containers.

Principles and uses
XLD Agar (Xylose Lysine Desoxycholate Agar) is prepared according to the formulation of the ISO 6579 norm. It is recommended for the identification of Salmonella in food products, after pre-enrichment in a non-selective fluid such as Buffered Peptone Water and enrichment in a selective fluid medium such as Muller Kauffmann Broth Base with Brilliant Green & Novobiocin (MKTTN), Rappaport Soy Broth (Vassiliadis)  or Modified Semisolid Rappaport Vassiliadis Medium (MSRV).
The reactions are the degradation of the three fermentable carbohydrates: xylose, lactose, and sucrose, with the production of acid, manifested in the color change from red to yellow. Sodium thiosulfate serves as a reactive substance with Ferric ammonium citrate as an indicator of the formation of hydrogen sulfide under alkaline conditions. Lysine is included to enable the Salmonella group to be differentiated from the non-pathogens since, in its absence, salmonellae would quickly ferment the xylose, making it indistinguishable from non-pathogenic species. After the salmonellae terminate the xylose present, the lysine is attacked through the enzyme lysine decarboxylase with a change to an alkaline pH, similar to the Shigella reaction. The bacteria that decarboxylate the L-Lysine to cadaverine are identified by the presence of a purple-red color around the colonies due to the elevation of the pH. Phenol red is the pH indicator. Yeast extract is a source of vitamins, particularly of the B-group essential for bacterial growth. Sodium chloride supplies essential electrolytes for transport and osmotic balance. Sodium desoxycholate is the selective agent and is thus inhibitory to Gram-positive microorganisms. Bacteriological Agar is the solidifying agent.
Typical colonies of Salmonella on XLD agar have a black center and lightly transparent zone of reddish color due to the color change of the indicator.
Salmonella H2S-negative variants grown on XLD agar are pink with a darker pink center. Lactose-positive Salmonella grown on XLD agar are yellow with or without blackening.

Preparation
Suspend 54 grams of the medium in one liter of distilled water Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. AVOID OVERHEATING. DO NOT AUTOCLAVE.Cool the medium according to the applicable normative and pour into Petri dishes as soon as it has cooled.
Preparation of large volumes, overheating and prolonged storage in water bath is to be avoided. Precipitates may be formed but do not affect the performance of the culture media.

Principles and uses
Salmonella Shigella Agar (SS Agar) is a selective and differential medium widely used in sanitary bacteriology to isolate Salmonella and Shigella from feces, urine, and fresh and canned foods.
Due to its strong inhibitory power, a heavy inoculum can be used in the SS agar. It must also be streaked in parallel, in less selective media such as Deoxycholate Agar, MacConkey Agar, Methylene Blue Eosin Agar (EMB), XLD Agar and Enteric Hektoen Agar , to increase the probability of detection when the population of microorganisms is scarce.
Beef extract and peptone mixture provide nitrogen, vitamins, minerals and amino acids essential for growth. Lactose is the fermentable carbohydrate providing carbon and energy. Bile salts mixture, sodium citrate and brilliant green inhibit Gram-positive bacteria, most coliform bacteria and swarming
Proteus spp., while allowing Salmonella spp to grow. Neutral red is the pH indicator. Sodium thiosulfate and ferric citrate allow the detection of the H2S producing bacteria.
Non-lactose fermenting bacteria (supposed pathogens, such as Shigella and the majority of salmonellae) produce clear colonies, transparent or colorless, while coliforms like E. coli are sufficiently inhibited, and form small colonies that vary from pink to red in color. Enterobacter and Klebsiella bacteria will produce larger colonies than E.coli, mucoid, pale and opaque cream to pink in colour. Colonies from Proteus and some strains of Salmonella will present black centers and a clear halo.
This formulation, highly selective, is not recommended for the primary isolation of Shigella. Some Shigella spp. may be inhibited

Preparation
Suspend 60 grams of the medium in one liter of distilled water. Mix well until a homogeneous suspension is obtained. Heat with frequent agitation and boil for one minute until complete disolution. DO NOT AUTOCLAVE. Cool to 45-50 °C and distribute in Petri dishes.

ChromoGel™ Salmonella RB Agar is a selective medium used for the
isolation and identification of Salmonella from food and animal feed,
water and other materials.

The agar is chromogenic, providing two chromogenic substrates – propylene glycol and X-Gal ((5-bromo-4-chloro-3-indoyl- β-D-galactopyranoside).
Certain Salmonella species act on the propylene glycol producing acid which causes the pH indicator in the media to change color, and pinkish-red or crimson colonies appear. Additionally, other members of the family Enterobacteriaceae which are positive for the enzyme β-D-galactosidase cleave the substrate X-Gal and this results in the production of blue-green colonies.
Salmonella species that are positive for the β-D-galactosidase enzyme and can produce acid from propylene glycol appear as purple-violet colonies, while species that are capable of neither appear as yellow or colorless colonies.

Application

• The detection of Salmonella in foodstuff, water, animal feed
• The differential diagnosis of Salmonella species in various samples

A liquid enrichment used for isolating Salmonella typhi and other Salmonella spp. from a variety of sources such as feces, urine, and food. Enzymatic Digest of Casein and Animal Tissue supply nitrogenous substances and carbohydrates for bacterial growth. Sodium Phosphate stabilizes pH and reduces toxicity to Selenite. Sodium Selenite inhibits growth of Gram-positive microorganisms such as coliforms and fecal Streptococci. Lactose is the fermentable carbohydrate and maintains an optimal pH by neutralizing the alkalinization occurring upon Selenite reduction.

Tetrathionate Broth Base, otherwise known as TT Broth, is used with an iodine-iodide solution for the cultivation of Salmonella spp. from clinical specimens, foods and other materials of sanitary importance. Enzymatic Digest of Casein and Animal Tissue supply nitrogenous substances and carbohydrates for bacterial growth. Upon addition of Iodine and Potassium Iodide, the Sodium Thiosulfate in this medium produces tetrathionate. Only microorganisms containing the enzyme tetrathionate reductase will proliferate in this medium. Bile Salts suppress the growth of coliforms and Gram-positive organisms. Calcium Carbonate neutralizes acid pH and absorbs toxic metabolites.

Salmonella Enrichment is a special formulation of Buffered Peptone Water that has been created and controlled for optimal detection of Salmonella in food products and feed.
Salmonella Enrichment with Tween®80 is used as enrichment medium for Salmonella analysis of products whose fat content exceeds 20%.

Selenite cystine broth is a modification of selenite F broth and is for the selective enrichment of Salmonellae spp. from clinical, food and environmental specimens.
The peptone acts as a nitrogen, carbon and vitamin source. Lactose is a fermentable carbohydrate and sodium phosphate is a buffer. L-cystine is used to enhance the recovery of Salmonellae spp. in low numbers. The medium is made selective by the addition of sodium biselenite (KM8021).
Following overnight incubation subculture(s) are usually made on to one or more of the many selective enteric solid media.

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Hektoen enteric agar was developed by King and Metzger as a differential selective medium for the isolation of Shigella spp. and Salmonella spp. species from enteric pathological samples.

The meat peptone and yeast extract provide the required nitrogen, carbon and vitamins. Lactose, sucrose and salicin are fermentable carbohydrates. Bromothymol blue is added as a pH indicator

in order to identify carbohydrate fermenting organisms. The combination of ferric ammonium citrate and sodium thiosulfate allows the production of hydrogen sulphide. Hydrogen sulphide positive colonies produce black centred colonies. Sodium chloride maintains the osmotic balance. The bile salts and acid fuchsin inhibit Gram-positive organisms.

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Rappaport-Vassiliadis (MSRV) Medium Semi-Solid is a modification of Rappaport-Vassiliadis Soy Broth for detecting motile Salmonella spp. in faeces and food products.[1]
The original research on MSRV Medium revealed a semi-solid could be used as a rapid and sensitive test for isolating motile Salmonella spp. from food products following pre-enrichment or selective enrichment.[2]

The semi-solid medium allows motility to be detected as halos of turbid growth around the original point of inoculation.
The peptones are to provide vitamins, nutrients and nitrogen to encourage growth of Salmonella spp.
The salt maintains the osmotic balance and potassium dihydrogen phosphate is a buffer for stabilising the pH of the medium.
Malachite green is included as a selective agent that inhibits Gram-positive organisms and some Gram-negative organisms.

References
(1) ISO 6579-1:2017. Microbiology of the food chain – Horizontal method for the detection, enumeration and serotyping of Salmonella – Part 1: Detection of Salmonella spp.
(2) De Smedt J.M., Bolderdikj R., Rappold H. and Lautenschlaeger D. 1986. Rapid Salmonella Detection in Foods by Motility Enrichment on a Modified Semi-Solid Rappaport-Vassiliadis Medium. J. Food Prot. 49:510-514

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XLT4 (Xylose-Lysine-Tergitol 4) Agar is a selective isolation medium for the detection of Salmonella, except for Salmonella Typhi and Paratyphi.
XLT4 agar can be used as the second media of choice in the normalized methods of Salmonella detection in food microbiology. It is also used as media of choice in animal health for Salmonella detection.

Principles and uses
XLT4 Agar Base with Tergitol 4 supplement, was developed in 1990 by Miller and Tate. It is a highly selective medium for isolating Salmonella from competing bacteria such as Proteus. They reported the isolation of non-typhi Salmonella from chicken and farm environmental drag-swab samples from heavily contaminated samples.
XLT4 Agar can be used clinically to screen stool samples for non-typhoid Salmonella. This medium allows the optimum growth of Salmonella. Differentiation of Salmonella from other organisms in this medium is based on the fermentation of carbohydrates (Lactose, Xylose, Sucrose) with the resulting production of hydrogen sulfide. H2S production is detected by the reaction of the iron salt, colonies appearing black or black-centered. Sodium thiosulfate and ferric ammonium citrate are the H2S indicators. The bacteria that decarboxylate the L-Lysine to cadaverine are identified by the presence of a purple-red color around the colonies due to the elevation of the pH. Phenol red is the pH indicator. Sodium thiosulfate is also added as a source of inorganic sulfur. Yeast extract and peptone are a nitrogen and amino acids source. Bacteriological agar is the solidifying agent. XLT4 Supplement  is added to inhibit the growth of non-Salmonella organisms.
Typical Salmonella colonies (H2S-positive) appear black or black-centered with a yellow halo after 18-48 hours of incubation at a temperature of 35±2 ºC. Upon continued incubation, the colonies become entirely black or pink to red with black centers. Colonies of H2S-negative Salmonella strains appear pink-yellow.
Most Citrobacter colonies are yellow without evidence of blackening. The growth of Enterobacter aerogenes and Escherichia coli is markedly inhibited; colonies that grow in this medium appear yellow without evidence of blackening. The growth of Proteus, Pseudomonas and Yersinia enterocolitica is markedly to completely inhibited. Shigella species are partially inhibited and colonies appear red.

Preparation
Suspend 59 grams of the medium in one liter of distilled water. Add 4,6 ml of XLT4 Supplement  (26-28% solution of 7-ethyl-2-methyl-4-undecanol hydrogen sulfate, sodium salt; formerly Tergitol 4). Mix well and heat with frequent agitation until completely dissolved. Boil for one minute. AVOID OVERHEATING. DO NOT AUTOCLAVE. Distribute into sterile Petri dishes

XLD (Xylose Lysine Desoxycholate) Agar is used for the isolation of Salmonella in pharmaceutical products. The typical composition corresponds to that defined in the American and European Pharmacopeia.
The agar can also be used as a second media of choice in the normalized methods for the detection of Salmonella in food products and water. 
A second formulation of XLD agar exists and corresponds to the composition in the standards, in food microbiology and in water microbiology

Salmonella-Shigella (SS) agar is used for the isolation of Salmonellae and Shigellae in fecal material. It can also be used as a second media of isolation in the context of standardized methods for the detection of Salmonella. 

Rappaport-Vassiliadis Soja Broth is used for the selective enrichment of Salmonella in milk, dairy products, other food products, water and in environmental samples.

Müller & Kauffmann Tetrathionate broth is one the oldest media traditionally used for the selective enrichment of Salmonella.

MKTTn Broth is used as one of two selective enrichment medium, along with RVS broth, for salmonellae in milk and dairy products and in other food products following the horizontal method described in the ISO 6579 standard. Associated with MSRV medium, it is also used in the protocol for the isolation and identification of Salmonella in animal production environments, in poultry and in mammals.
MKTTn broth is also used as a second selective enrichment broth for the detection of Salmonella in waters.

Modified Semi-Solid Rappaport-Vassiliadis Agar (MSRV) is a selective medium historically used for the isolation of Salmonella in chocolate and other food products. It is also widely used in animal health: in particular with mammals, poultry and in animal production facilities. It is also recommended for us in the detection of motile Salmonellae in animal fecal matter and in environmental samples in the context of primary animal production.  
This medium is not recommended for immobile Salmonellae (Salmonella Gallinarum et Pullorum)

Principles and uses
Modified Semisolid Rappaport Vassiliadis Medium (MSRV) is a selective medium used for the rapid detection of motile Salmonella spp.
Is a modification of Rappaport Vassiliadis enrichment broth for detecting motile Salmonella spp in feces, food products and environmental samples. In this medium the main detection is based on the motility and ability of Salmonella to migrate through selective medium ahead of competing motile microorganism, therefore producing opaque halos of growth.
The mobility of other microorganisms is inhibited by selective mediums (such as magnesium chloride, malachite green oxalate and novobiocin) as well as by the temperature of incubation at 42 °C. Tryptose and acid casein peptone provide nitrogen, vitamins, minerals and amino acids essential for growth. Sodium chloride supplies essential electrolytes for transport and osmotic balance. Magnesium chloride and malachite green oxalate are inhibitory to organisms other than Salmonella spp. Novobiocin is a selective agent that inhibits gram positive bacteria and avoids the development of Proteus. This medium is not suitable for the detection of non motile strains of Salmonella whose of which their presence is very low (= 1 %). It is recommended to conduct serological and biochemical tests for Salmonella species confirmation.

Preparation
Suspend 31,6 grams of the medium in one liter of distilled water. Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. AVOID OVERHEATING. DO NOT AUTOCLAVE. Dispense into Petri plates.

Hektoen Enteric Agar is a selective medium for the isolation and differentiation of pathogenic enterobacteria from biological samples of animal origin, water samples, dairy products and other food products. It is used in animal health in the context of Salmonella detection in mammals. 
The medium is also recommended for the detection of Shigella, in food microbiology.
Hektöen Enteric agar can also be used as the second media of choice in the standardized methods for the detection of Salmonella. 

Brilliant Green agar according to Edel & Kampelmacher is a selective medium used to isolate Salmonella in milk and dairy products.
This media can also be used as a second isolation media in the context of the various normalized methods for the detection of Salmonella spp.