Principles and uses A1 Medium, also known as A1 Broth, is used for the detection of fecal coliforms in water samples. The enumeration of coliforms, specifically Escherichia coli, has been used to determine water purity by the most-probable-number method. This medium was created to hasten the recovery time of E. coli and to reduce the number of false positive cultures. A-1 Medium can be used in a single-step procedure, also in foods, not requiring a previous enrichment step. Tryptone provides nitrogen, vitamins, minerals and aminoacids. Lactose is the carbon source and in combinationwith salicin, provides energy for organism growth. Ecosurf is a surfactant and sodium chloride supplies essential electrolytes for transport and osmotic balance. Gas production is a positive reaction indicating the presence of Coliforms. Gas may be produced inside the Durham tubes or may appear as dissolved gas that forms gas bubbles when slightly agitated.
Preparation Suspend 31,5 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. Dispense into tubes with Durham gas collecting tubes and sterilize in autoclave at 121 ºC for 15 minutes.
Formula
Tryptone: 20.0
Lactose :5.0
Bile Salts No. 3 :1.5
Di-potassium phosphate :4.0
Mono-potassium phosphate :1.5
Sodium chloride :5.0
Directions
Dissolve 37 g in 1 litre of distilled water. Dispense into final containers and sterilize by autoclaving at 121oC for 15 minutes.
For the detection of Escherichia coli in water and food samples by a fluorogenic method.
EC Medium EC Medium, otherwise known as EC Broth, is used to detect the presence of coliform bacteria in drinking water, wastewater, and foods. Developed by Hajna and Perryl, it was designed for coliform bacteria, specifically E. coli. A buffered Lactose broth, it contains Bile Salts to inhibit Gram-positive bacteria and spore-forming microorganisms while enhancing that of E. coli. Coliforms can be detected by growth at 37°C, while Escherichia coli are detected by growth at 44.5°C. Dipotassium Phosphate and Monopotassium Phosphate act as buffering agents while Sodium Chloride maintains the osmotic balance of the medium.
Lauryl Sulfate Broth with MUG is a liquid medium used for the detection of Escherichia coli in water, food, and dairy products. Enzymatic Digest of Casein offers a source of nitrogen, vitamins, and minerals. Potassium Phosphates act as buffering agents and Lactose is a source of energy. Sodium Lauryl Sulfate suppresses the growth of organisms other than coliforms. Addition of the fluorogenic compound MUG (4-methylumbelliferyl-β-D-glucuronide) permits the rapid detection of E. coli through observation under UV light. MUG is degraded to 4-methylumbelliferone, a fluorescent end product, by the enzyme β-D-glucuronidase encoded in the genome of E. coli.
rypto Soy Agar, otherwise known as Tryptic Soy Agar or Trypticase Soy Agar, is a general growth medium prepared with or without enrichments. It is used for the isolation of different strains of fastidious microorganism. Enzymatic Digest of Casein and Soy Peptone provide amino acids, peptides, and other nitrogenous substances. Sodium Chloride provides essential electrolytes and maintains osmotic equilibrium. TSA with 5% Sterile Sheep Blood is useful for the isolation and determination of hemolytic reactions by Staphylococcus and Streptococcus spp. from the respiratory tract, blood, cerebrospinal fluid and minor lesions.
Tryptose Phosphate Broth is a liquid medium recommended for the cultivation of fastidious microorganisms. Enzymatic Digest of Casein, Soy Peptone, and Yeast Extract supply most of the nutrients for bacterial growth (amino acids, peptides, carbohydrates, vitamins, and minerals). Dextrose is the main carbohydrate source. Sodium Chloride provides essential electrolytes and maintains osmotic equilibrium. Disodium Phosphate acts as pH buffer. The addition of 0.1 – 0.2% Agar concentration can aid in the recovery of anaerobes.
Violet Red Bile Agar with MUG is often abbreviated as VRBA w/ MUG. This medium is used for the fluorogenic detection of Escherichia coli in food, milk, water, and other sanitary materials. Like Violet Red Bile Agar, it is a selective medium which detects the growth of Lactose-fermenting coliforms. Coliform colonies lower the pH of the medium, thus causing their colonies to look red (neutral red dye). Crystal Violet and Bile Salts inhibit the growth of Gram-positive microorganisms, while the addition of 4-methylumbelliferyl-β-D-glucuronide (MUG) allows for the rapid detection of E. coli. MUG is used as a substrate to detect glucuronidase activity, since its degradation by this enzyme produces the fluorescent compound 4-methylumbelliferone, visible under UV light.
This is a selective medium for the isolation and differentiation of bile tolerant Gram-negative (enteric) and Gram-positive (staphylococci and enterococci) organisms and has uses in all areas of bacteriology. This medium is recommended by the World Health Organisation and the Department of Health for the bacteriological examination of water.
It has the disadvantage that many strains of Proteus spp. will spread on it and for this reason MacConkey Agar without salt and crystal violet may be preferred (KM0011
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MacConkey agar No. 3 is a selective medium primarily for the isolation of Enterobacteriacae from waters and sewage. This media differs from the original MacConkey formulation in that as well as bile salts, crystal violet has been included as an additional selective agent. This has the effect of inhibiting Gram-positive organisms.
The peptone acts as a nitrogen, carbon and vitamin source. Sodium chloride maintains osmotic balance. Lactose is a carbohydrate and during its fermentation causes a confined pH drop around the bacterial colony. This causes a colour change in the pH indicator, neutral red and bile precipitation.
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Chromogenic coliform agar (CCA) conforms to the ISO 9308-1 guidelines for the detection, enumeration and isolation of coliforms and more specifically Escherichia coli in water samples by the membrane-filtration technique.
The colonial differentiation is provided by the chromogenic substrates, Salmon-GAL and X-glucuronide.
Salmon-GAL is used for the detection of ß-D-galactosidase enzymatic activity.
X-glucuronide is used for the detection of ß-D-glucoronidase enzymatic activity.
β-D-galactosidase, expressed by all coliforms, cleaves the Salmon-GAL substrate and producing red/pink coloured colonies.
Unlike other coliforms, Escherichia coli cleaves both Salmon-GAL and X-glucuronide producing a violet/blue coloured colonies.
Tryptophan is used to increase detection reliability by improving the indole reaction.
The peptones, sodium pyruvate and sorbitol support bacterial growth and simple recovery of sub-lethal thermally injured coliforms.
Sodium di-hydrogen phosphate and di-sodium hydrogen phosphate phosphate buffer the medium and sodium chloride is used to achieve osmotic balance.
The selectivity is attained by the addition of Tergitol® 7 as it inhibits the growth of Gram-positive bacteria.
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This medium can be used as a screening method for the differentiation of enterobacteriaceae based on the ability of some species to utilise citrate as a sole source of carbon. It is often used as a screening test for Klebsiella pneumoniae (positive reaction) while Escherichia coli is negative.
Species that metabolize citrate as their sole source of carbon and ammonium as the sole source of nitrogen cause an increase in alkalinity of the medium resulting in a colour change from green to blue due to the presence of the pH indicator bromthymole blue.
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A selective medium for the enrichment of Enterobacteriaceae and the detection of Escherichia coli in pharmaceutical products. The inclusion of bromocresol purple indicator makes the colour change caused by acid production from the fermentation of lactose easy to read with gas formation. The presence of ox bile helps to suppress the growth of Gram-positive and non-enteric bacterial species. This formulation complies with the Harmonized USP/EP/JP.
Nitrogen is supplied by the gelatin peptone whilst lactose serves as the fermentable carbohydrate source. Oxbile is the selective agent helping to suppress Gram-positive organisms and bromocresol purple detects the pH change as a result of the fermentation of lactose.
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Sorbitol MacConkey agar is a differential medium for the isolation of Escherichia coli 0157:H7 based on the formulation by Rappaport and Henig. It differs from other MacConkey mediums in that lactose has been replaced by sorbitol. As Escherichia coli 0157:H7 does not ferment sorbitol it produces pale translucent colonies whereas most other strains of Escherichia coli are sorbitol positive and produce pink colonies. Although it should be noted that colonies that are sorbitol positive can revert and possibly be mistaken as sorbitol negative. Tryptone and meat peptone provide the required carbon, nitrogen and vitamins. Sorbitol is a fermentable carbohydrate and neutral red is a pH indicator. Bile Salts no.3 and crystal violet are selective agents and together inhibit Gram-positive cocci. Sodium chloride maintains the osmotic balance. If required, the selectivity of the medium may be increased by the addition of cefixime (0.05mg/L) and potassium tellurite (2.5mg/L).
Thành phần phù hợp với yêu cầu của phương pháp phân tích E.coli O157 hoặc theo ISO 16654, cụ thể thành phần trong mỗi lít môi trường pha chế như sau:
- Enzymatic digest of casein (hoặc Enzymatic digest of gelatin hoặc Peptone hoặc Tryptone hoặc Casein enzymic hydrosate): 17g
- Enzymatic digest of animal tissues (hoặc Peptic digest of meat hoặc Peptone hoặc Meat peptone): 3g
- Hoặc Enzymatic digest of casein: 1,5g và Enzymatic digest of animal Tissue: 1,5g
- Sorbitol (hoặc D-sorbitol): 10g
- Bile salts No.3 (hoặc Bile Salts Mixture): 1,5g
- Sodium chloride: 5g
- Neutral red: 0,03g
- Crystal violet: 0,001g
- Agar: 9-15g
– Giá trị pH: 7,1 + 0,2 ở 250C.
– Hiệu năng môi trường:
- Thông số hiệu suất: Vi khuẩn E.coli O157:H7 phát triển tốt (hoặc Pr > 50%), khuẩn lạc đặc trưng.
Thông số chọn lọc: Vi khuẩn Staphylococcus aureus không phát triển.
Recent developments in culture media have given rise to the use of chromogenic substrates as a means of differentiating bacteria
particularly among the coliform group of organisms. This is one such medium and has been developed as a selective medium for the isolation and enumeration of Escherichia coli without the need for membranes or pre-incubation. Based on the formulation of Tryptone Bile Agar it incorporates a chromogenic substrate, X-Glucuronide, to detect the ß-glucuronidase enzyme which is specific for the majority of E. coli strains. Approximately, 3-4% of E. coli are glucuronidase negative including E. coli O157.(1) The advantage of the chromogenic substrate is that the reaction is concentrated within the colony resulting in distinctive blue/green colonies of E. coli while the other coliforms produce cream colonies.
The tryptone provides the required carbon, nitrogen and vitamins. Bile salts No.3 is a selective agent against Gram-positive bacteria. X-glucuronide is a chromogenic substrate. Agar is solidifying agent.
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Bromocresol Purple (BCP) Lactose Agar is a non-selective medium, used for the differentiation of Enterobacteriaceae. It is used for the confirmation of coliforms in the context of the standard T90-425, for the bacteriological examination of containers and recipients used in water bottling.
Tryptophan broth allows the culture of microorganisms presenting no particular growth requirements. The media is used to perform the indole production test, used notably in the confirmation of Escherichia coli, Shigella and Salmonella.
TBX Agar is a selective medium for the enumeration of β-D-glucuronidase-positive Escherichia coli in food products. The result is obtained directly by counting characteristic colonies after only 24 hours of incubation and no confirmation step is required.
- Enzymatic digest of casein (hoặc Tryptone): 20g
- Bile salts No.3 (hoặc Bile Salt mixture): 1,5g
- 5-bromo-4-chloro-3-indolyl b- D-glucuronic acid (BCIG): 144µmol (hoặc: 0,075g cyclohexylammonium hoặc cyclohexylammonium salt hoặc X-Glucoronide hoặc X-b-D-glucuronic acid hoặc BCIG)
- Dimethyl sulfoxide (DMSO) (nếu có): 3ml
- Agar (hoặc Bacteriological agar): 9-18g
– Giá trị pH của môi trường hoàn chỉnh: 7,2 ± 0,2 ở 250C
Glutamate broth is used enumeration of β-glucuronidase positive E. coli in food products by the MPN technique. It is recommended when the microorganisms are found in a sub-optimal state due to exposition to stress including freezing, desiccation, disinfection or high salinity.
The described method does not allow the detection of strains of Escherichia coli that do not develop at 44°C, and, in particular, those that are β-glucuronidase negative, as the case of E. coli O157 and a few other strains of pathogenic E. coli.
EMB Agar, originally recommended by Levine, is used to isolate and identify enterobacteria (notably Escherichia coli and Enterobacter aerogenes) in pharmaceutical, cosmetic and food products as well as water.
It is also used as a confirmation media for Escherichia coli in cosmetic products.
EC Broth (abbreviation for Escherichia coli) is a selective media used for the confirmation of E. coli in water, milk and other food products, as well as live shellfish.
The typical composition of the broth responds to that defined in the normalized method of presumptive Escherichia coli enumeration.