Plot No. C40, Road No. 21Y, MIDC, Wagle Industrial Estate, Thane(W)-400604, MH, India
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Intended Use
Recommended for selective isolation and differentiation of E.coli and other enteric bacteria from pharmaceutical products in accordance with the microbial limit testing by harmonized methodology of USP/EP/BP/JP.
Composition**
| Ingredients | Gms / Litre |
|---|---|
| Gelatin peptone # | 17.000 |
| HMC peptone ## | 3.000 |
| Lactose monohydrate | 10.000 |
| Sodium chloride | 5.000 |
| Bile salts | 1.500 |
| Neutral red | 0.030 |
| Crystal violet | 0.001 |
| Agar | 13.500 |
| pH after sterilization (at 25°C) | 7.1±0.2 |
**Formula adjusted, standardized to suit performance parameters
# Pancreatic digest of gelatin
## Peptones (meat and casein)
Directions
Either streak, inoculate or surface spread the test inoculum (50-100 CFU) aseptically on the plate.
Principle And Interpretation
MacConkey Agar is the earliest selective and differential medium for cultivation of coliform organisms (1,2). Subsequently MacConkey Agar and Broth have been recommended for use in microbiological examination of foodstuffs (3) and for direct plating / inoculation of water samples for coliform counts (4). This medium is also accepted by the Standard Methods for the Examination of Milk and Dairy Products (5). It is recommended in pharmaceutical preparations and is in accordance with the harmonized method of USP/EP/BP/JP (6-9).
Gelatin peptone and HMC peptone provide the essential nutrients, vitamins and nitrogenous factors required for growth of microorganisms. Lactose monohydrate is the fermentable source of carbohydrate. The selective action of this medium is attributed to crystal violet and bile salts, which are inhibitory to most species of gram-positive bacteria. Sodium chloride maintains the osmotic balance in the medium.
After enrichment of Escherichia coli in MacConkey Broth (MH083), it is then subcultured on MacConkey Agar. 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 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 and transparent and typically do not alter appearance of the medium. Yersinia enterocolitica may appear as small, non-lactose fermenting colonies after incubation at room temperature.
Type of specimen
Pharmaceutical samples, Food and dairy samples; Water samples.
Specimen Collection and Handling
For food and dairy samples, follow appropriate techniques for sample collection and processing as per guidelines (3,5).
For water samples, follow appropriate techniques for sample collection and processing as per guidelines (4).
For pharmaceutical samples, follow appropriate techniques for sample collection, processing as per guidelines (6-9).
After use, contaminated materials must be sterilized by autoclaving before discarding.
Warning and Precautions:
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 specimens. Safety guidelines may be referred in individual safety data sheets.
Limitations
- Individual organisms differ in their growth requirement and may show variable growth patterns on the medium
- Each 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.
- It is recommended to store the plates at 24-30°C to avoid minimum condensation.
- Though the medium is recommended for selective isolation, further biochemical and serological testing must be carried out for complete identification.
- 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 MacConkey Agar in 90 mm disposable plates.
Colour of medium
Red with purplish tinge coloured medium
Quantity of medium
25 ml of medium in 90 mm disposable plates.
pH
6.90-7.30
Sterility Check
Passes release criteria
Cultural Response
Growth Promotion is carried out in accordance with the harmonized method of ICH (USP/EP/BP/JP). Cultural response was observed after an incubation at 30-35°C for 18-72 hours. Recovery rate is considered as 100% for bacteria growth on Soybean Casein Digest Agar.
Growth promoting properties
Growth of microorganism comparable to that previously obtained with previously tested and approved lot of medium occurs at the specified temperature for not more than the shortest period of time specified inoculating 100 cfu (at 30-35°C for <=18 hours).
Indicative properties
Colonies are comparable in appearance and indication reaction to those previously obtained with previously tested and approved lot of medium occurs for the specified temperature for a period of time within the range specified inoculating <=100 cfu (at 30-35°C for 18-72 hours).
| Organism | Inoculum (CFU) | Growth | Observed Lot value (CFU) | Recovery | Colour of colony | Incubation period |
|---|---|---|---|---|---|---|
| Growth Promoting + Indicative | ||||||
| Escherichia coli ATCC 8739 (00012*) | 50-100 | luxuriant | 25-100 | >=50% | pink-red with bile precipitate | 18-72 hrs |
| Additional Microbiological testing | ||||||
| Escherichia coli ATCC 25922 (00013*) | 50-100 | luxuriant | 25-100 | >=50% | pink to red with bile precipitate | 18 -24 hrs |
| # Klebsiella aerogenes ATCC 13048 (00175*) | 50-100 | luxuriant | 25-100 | >=50% | pink to red | 18-24 hrs |
| Enterococcus faecalis ATCC 29212 (00087*) | 50-100 | none - poor | 0-10 | <=10% | colourless to pale pink | 18 -24 hrs |
| Salmonella Typhimurium ATCC 14028 (00031*) | 50-100 | luxuriant | 25-100 | >=50% | colourless | 18 -24 hrs |
| Staphylococcus aureus subsp. aureus ATCC 6538 (00032*) | >=10³ | inhibited | 0 | 0% | >=24 hrs | |
| Staphylococcus aureus subsp. aureus ATCC 25923 (00034*) | >=10³ | inhibited | 0 | 0% | >=24 hrs | |
| Salmonella Enteritidis ATCC 13076 (00030*) | 50-100 | luxuriant | 25-100 | >=50% | colourless | 18 -24 hrs |
| Salmonella Paratyphi A ATCC 9150 | 50-100 | luxuriant | 25-100 | >=50% | colourless | 18 -24 hrs |
| Salmonella Paratyphi B ATCC 8759 | 50-100 | luxuriant | 25-100 | >=50% | colourless | 18 -24 hrs |
| Salmonella Typhi ATCC 6539 | 50-100 | luxuriant | 25-100 | >=50% | colourless | 18 -24 hrs |
| Salmonella Abony NCTC 6017 (00029*) | 50-100 | luxuriant | 25-100 | >=50% | colourless | 18 -24 hrs |
| Proteus vulgaris ATCC 13315 | 50-100 | luxuriant | 25-100 | >=50% | colourless | 18 -24 hrs |
| Shigella flexneri ATCC 12022 (00126*) | 50-100 | fair to good | 15-40 | 30-40% | colourless | 18 -24 hrs |
| Staphylococcus epidermidis ATCC 12228 (00036*) | >=10³ | inhibited | 0 | 0% | >=24 hrs | |
| Corynebacterium diphtheriae type gravis | >=10³ | inhibited | 0 | 0% | >=24 hrs | |
Key :- (#) Formerly known as Enterobacter aerogenes, (*) Corresponding WDCM numbers
Storage and Shelf Life
On receipt store between 20-30°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 sample must be decontaminated and disposed of in accordance with current laboratory techniques (10,11).
| Product Name | MacConkey Agar Plate |
|---|---|
| SKU | MPH081 |
Write Your Own Review
How does crystal violet prevent Proteus swarming?
Proteus species (P. mirabilis, P. vulgaris) produce urease and exhibit characteristic swarming motility on standard agar - rapidly spreading thin film that can cover entire plate obscuring other colonies. Crystal violet inhibits this swarming by: (1) Interfering with flagellar function, (2) Partially inhibiting growth rate, (3) Disrupting cell membrane processes. On MacConkey with increased crystal violet, Proteus produces discrete non-swarming colonies instead of spreading growth. This allows identification of other organisms (E. coli, Salmonella, Klebsiella) that would otherwise be obscured. Critical for clinical urine cultures where Proteus common.
What is MacConkey with Crystal Violet?
MacConkey Agar with Crystal Violet has increased crystal violet concentration for enhanced selectivity against gram-positive bacteria and swarming of Proteus species. Standard MacConkey contains 1mg/L crystal violet; this formulation has higher amounts. Benefits: (1) Better inhibition of gram-positives (especially from heavily contaminated samples), (2) Prevents Proteus swarming (which can obscure other colonies), (3) Cleaner plates for colony picking. Use when: heavy gram-positive contamination expected, Proteus swarming is problem, pharmaceutical/clinical samples. May slightly reduce recovery of some sensitive gram-negatives.
How many plates do I need for my testing volume?
Calculate based on testing frequency: Daily Water testing (10 samples × 2 plates = 20 plates/day = 140/week = 600/month). Food testing batch (25 samples × 2-3 plates = 50-75 plates/batch). Add 20% for QC controls, retests, and contamination. Example: 300 plates/month needed → order 6 packs of 50-plate (300 total) or mix of 50-plate and 20-plate packs. Consider shelf life (4 months) when bulk ordering.
What is the difference between 20-plate and 50-plate packs?
Both contain identical MacConkey Agar formulation. The 50-plate pack (MPH081-50PT) offers: (1) Lower cost per plate for high-volume users, (2) Reduced ordering frequency, (3) Consistent lot numbers across more tests, Choose 50-plate packs for: routine daily testing, high-throughput food/Water labs, environmental monitoring programs with many sample points. Choose 20-plate packs for: low-medium volume testing, limited storage space, shorter shelf-life needs, or when testing multiple media types.
Can I use MacConkey Agar for environmental monitoring in pharmaceutical facilities?
Yes, MacConkey is commonly used for environmental monitoring to detect gram-negative bacteria in cleanrooms, Water systems, and non-sterile manufacturing areas. It helps identify contamination from personnel (fecal coliforms), Water sources (Pseudomonas, coliforms), or biofilm formation. For pharmaceutical EM programs, use MacConkey in combination with TSA (total aerobes), SDA (fungi), and Mannitol Salt Agar (Staph). Incubate and read per your validated SOP. Document negative results or investigate positive findings.
Is this product suitable for FDA BAM and AOAC methods?
Yes, HiMedia MacConkey Agar RTU is manufactured to meet specifications for FDA Bacteriological Analytical Manual (BAM), AOAC Official Methods, ISO standards, and USP requirements. Each lot is performance-tested with ATCC reference strains (E. coli ATCC 8739 for lactose fermentation, and Staphylococcus aureus ATCC 6538 ). Certificates of Analysis document compliance with method specifications. Widely used in food, pharmaceutical, and microbiology laboratories.
What are the advantages of RTU plates vs preparing MacConkey from dehydrated powder?
RTU Mac Conkey Agar plates eliminate: (1) 2-3 hours media preparation time, (2) Autoclaving requirements, (3) Plate pouring and cooling, (4) QC testing of each batch prepared, (5) Contamination risk during preparation, (6) Batch-to-batch variability from manual preparation. RTU plates arrive pre-poured, sterilized, QC-tested with guaranteed performance. Ideal for labs with limited prep facilities, GMP requirements, or inconsistent in-house media quality. Cost-effective for low-medium volume testing.
How should MacConkey Agar RTU plates be stored?
Store MacConkey RTU plates at 20-25°C in original sealed packaging protected from light. Shelf life is typically 3-6 2-4 months from manufacture date. Do not freeze. Before use, allow plates to equilibrate to room temperature and check for: (1) No contamination, (2) No excessive moisture on agar surface, (3) Pink color maintained, (4) No cracks or shrinkage. Inspect expiration date on each sleeve. Discard plates showing dryness, discoloration, or contamination.
What organisms grow on MacConkey Agar?
MacConkey supports gram-negative bacteria: Lactose fermenters (pink): E. coli, Klebsiella pneumoniae, Enterobacter spp., Citrobacter spp. Non-lactose fermenters (colorless): Salmonella spp., Shigella spp., Proteus spp., Pseudomonas aeruginosa, Yersinia spp. Gram-positive bacteria (Staphylococcus, Streptococcus, Bacillus, Enterococcus) are inhibited by bile salts and crystal violet. Some gram-positive organisms may show minimal growth but are easily distinguished.
What is the incubation temperature and time for MacConkey Agar?
Incubate MacConkey Agar at 30-35°C for 18-72 hours aerobically. For growth promoting incubate for >=18 hours, for characteristic colonies incubate for 18-72 hours. For inhibitory properties check for >=72 hours. For Water testing, some protocols use 30-35°C. For food testing, follow specific method requirements (FDA BAM, AOAC, ISO). Check colonies after 18-24 hours for optimal differentiation.
Why is MacConkey Agar pink and what causes colonies to turn pink?
MacConkey Agar contains neutral red, pH indicator that turns pink under acidic conditions. Lactose-fermenting bacteria (E. coli, Klebsiella, Enterobacter) ferment lactose producing acid, which lowers pH and turns colonies and surrounding medium pink/red. Non-lactose fermenters (Salmonella, Shigella, Pseudomonas) produce colorless colonies. The medium itself is pale pink due to the neutral red. This differential property allows rapid presumptive identification of enteric pathogens.
What is MacConkey Agar used for?
MacConkey Agar i recommended for selective isolation and differentiation of E.coli and other enteric bacteria from pharmaceutical products in accordance with the microbial limit testing by harmonized methodology of USP/EP/BP/JP. It selectively inhibits gram-positive bacteria using bile salts and crystal violet, while differentiating lactose-fermenting bacteria (appear pink/red) from non-lactose fermenters (appear colorless/pale).