MacConkey Agar

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SKU:
SM081


Intended Use

Recommended for the selective isolation and differentiation of coliform organisms and other enteric pathogens from clinical and non-clinical samples.

Composition**

Ingredients g/L
Gelatin peptone 17.000
Tryptone 1.500
Peptone 1.500
Lactose 10.000
Bile salts 1.500
Sodium chloride 5.000
Neutral red 0.030
Crystal violet 0.001
Agar 15.000
Final pH (at 25°C) 7.1±0.2

**Formula adjusted, standardized to suit performance parameters

Directions

MacConkey Agar w/ 0.15% Bile salts, CV and NaCl is a ready to use solid media in glass bottle. The medium is pre-sterilized, hence it does not need sterilization. Medium in the bottle can be melted either by using a pre-heated water bath or any other method. Slightly loosen the cap before melting. When complete melting of medium is observed dispense the medium in tubes as butts /slants or in plates as desired and allow to solidify. If on plate, either streak, inoculate or surface spread the test inoculum (50-100 CFU) aseptically.

Principle And Interpretation

MacConkey agars are slightly selective and differential plating media mainly used for the detection and isolation of gram-negative organisms from clinical (1), dairy (2), food (3,4), water (5), pharmaceutical (6,7) and industrial sources (8). It is also recommended for the selection and recovery of the Enterobacteriaceae and related enteric gram-negative bacilli. USP recommends this medium for use in the performance of Microbial Limit Tests (7).

These agar media are selective since the concentration of bile salts, which inhibit gram-positive microorganisms, is low in comparison with other enteric plating media. The medium M081, which corresponds with, that recommended by APHA can be used for the direct plating of water samples for coliform bacilli, for the examination of food samples for food poisoning organisms (4) and for the isolation of Salmonella and Shigella species in cheese (2). Other than that this medium is also used for count of coli-aerogenes bacteria in cattle and sheep faeces (9), the count of coli-aerogenes and non-lactose fermenters in poultry carcasses (9), bacterial counts on irradiated canned minced chicken (10) and the recognition of coli-aerogenes bacteria during investigations on the genus Aeromonas (11,12).

MacConkey Agar is the earliest selective and differential medium for cultivation of enteric microorganisms from a variety of clinical specimens (13,14). The original medium contains protein, bile salts, sodium chloride and two dyes. The selective action of this medium is attributed to crystal violet and bile salts, which are inhibitory to most species of gram-positive bacteria. Gram-negative bacteria usually grow well on the medium and are differentiated by their ability to ferment lactose. Lactose-fermenting strains grow as red or pink colonies and may be surrounded by a zone of acid precipitated bile. The red colour is due to production of acid from lactose, absorption of neutral red and a subsequent colour change of the dye when the pH of medium falls below 6.8. Lactose non-fermenting strains, such as Shigella and Salmonella are colourless, transparent and typically do not alter appearance of the medium.

Peptone, Tryptone and gelatin peptone are sources of nitrogen, carbon, long chain amino acids and other nutrients. Lactose is a fermentable carbohydrate, Sodium chloride maintains the osmotic equilibrium. Bile salts and crystal violet are selective agents that inhibit growth of gram-positive organisms. Neutral red is the pH indicator dye.

Type of specimen

Clinical - faeces, urine and other pathological material, foodstuffs and dairy samples, water samples, pharmaceutical samples.

Specimen Collection and Handling

For clinical samples follow appropriate techniques for handling specimens as per established guidelines (1,15). For food and dairy samples, follow appropriate techniques for sample collection and processing as per guidelines (2,4). For water samples, follow appropriate techniques for sample collection, processing as per guidelines and local standards (5). For pharmaceutical samples, follow appropriate techniques for sample collection, processing as per guidelines (6,7). After use, contaminated materials must be sterilized by autoclaving before discarding.

Warning and Precautions

In Vitro diagnostic use. For professional use only. Read the label before opening the pack. Wear protective gloves/ protective clothing/eye protection/face protection. Follow good microbiological lab practices while handling specimens and culture. Standard precautions as per established guidelines should be followed while handling clinical specimens. Safety guidelines may be referred in individual safety data sheets.

Limitations

  • 1.Individual organisms differ in their growth requirement and may show variable growth patterns on the mediumEach lot of the medium has been tested for the organisms specified on the COA. It is recommended to users to validate the medium for any specific microorganism other than mentioned in the COA based on the user's unique requirement.
  • 2.It is recommended to store the plates at 24-30°C to avoid condensation.
  • 3.Though the medium is recommended for selective isolation, further biochemical and serological testing must be carried out for further confirmation.
  • 4.The surface of the medium should be dry when inoculated.

Performance and Evaluation

Performance of the medium is expected when used as per the direction on the label within the expiry period when stored at recommended temperature.

Quality Control

Appearance
Sterile glass bottle containing slightly opalscent MacConkey Agar

Colour of medium
Red with purplish tinge coloured medium

Quantity of medium
100ml of medium in glass bottle.

pH
6.90-7.30

Sterility Check
Passes release criteria

Cultural Response
Cultural charactistics observed after melting the medium and pouring into sterile petri plates. The plates are inoculated with following test organisms and incubation at 35-37°C for 18-24 hours. Recovery rate is considered as 100% for bacteria growth on Soybean Casein Digest Agar.

Organism Inoculum (CFU) Growth Recovery Colour of colony
Corynebacterium diphtheriae type gravis >=104 inhibited 0%
Shigella flexneri ATCC 12022 (00126*) 50-100 fair to good 30-40% colourless
Salmonella Paratyphi A ATCC 9150 50-100 luxuriant >=50% colourless
Salmonella Abony NCTC 6017 (00029*) 50-100 luxuriant >=50% colourless
## Proteus hauseri ATCC 13315 50-100 luxuriant >=50% colourless
Salmonella Typhi ATCC 6539 50-100 luxuriant >=50% colourless
Staphylococcus epidermidis ATCC 12228 (00036*) >=104 inhibited 0%
Escherichia coli ATCC 8739 (00012*) 50-100 luxuriant >=50% pink-red with bile precipitate
Staphylococcus aureus subsp.aureus ATCC 6538 (00032*) >=104 inhibited 0%
Salmonella Paratyphi B ATCC 8759 50-100 luxuriant >=50% colourless
Escherichia coli ATCC 25922 (00013*) 50-100 luxuriant >=50% pink to red with bile precipitate
# Klebsiella aerogenes ATCC 13048 (00175*) 50-100 luxuriant >=50% pink to red
Salmonella Typhimurium ATCC 14028 (00031*) 50-100 luxuriant >=50% colourless
Enterococcus faecalis ATCC 29212 (00087*) 50-100 none - poor <=10% colourless to pale pink
Salmonella Enteritidis ATCC 13076 (00030*) 50-100 luxuriant >=50% colourless
Staphylococcus aureus subsp.aureus ATCC 25923 (00034*) >=104 inhibited 0%

Key :- * Corresponding WDCM numbers,
(##) Formerly known as Proteus vulgaris
(#) Formerly known as Enterobacter aerogenes

Storage and Shelf Life

On receipt store between 15-30°C. Use before expiry date on the label. Product performance is best if used within stated expiry period.

Disposal

User must ensure safe disposal by autoclaving and/or incineration of used or unusable preparations of this product. Follow established laboratory procedures in disposing of infectious materials and material that comes into contact with clinical sample must be decontaminated and disposed of in accordance with current laboratory techniques (1,15).

More Information
Product Name MacConkey Agar
SKU SM081
Customized Product Available No
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