HiMedia Laboratories GmbH, Marie-Curie-Str. 3, 64683, Einhausen, Germany.
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Composition**
| Ingredients | Gms / Litre |
|---|---|
| Casein enzymic hydrolysate | 20.000 |
| Lactose | 5.000 |
| Sodium chloride | 5.000 |
| Salicin | 0.500 |
| Polyethylene glycol p-isooctylphenyl ether (Triton X 100) | 1.000 |
| Final pH (at 25°C) | 6.9±0.1 |
**Formula adjusted, standardized to suit performance parameters
Directions
Suspend 31.5 grams in 1000 ml distilled water. Heat if necessary to dissolve the medium completely. Distribute 10 ml amounts into tubes containing inverted Durham's tubes. Sterilize by autoclaving at 15 lbs pressure (121°C) for 10 minutes.
Principle And Interpretation
Escherichia coli is used as the indicator organism to detect the faecal contamination of water. Andrews and Presnell (1) devised A-1 Medium, which was capable of recovering Escherichia coli from estuarine waters in 24 hours instead of 72 hours by avoiding the pre-enrichment step as recommended by APHA (2). This greatly reduced the time required for the complete identification of E. coli (3) by the elevated temperature and most probable number (MPN) methods, routinely used for water analysis. A-1 Medium substantially reduces the incidence of false positive cultures. Also, Stanbridge and Delfino found that the results obtained by using 3-hours pre-incubation step (using A-1 Medium) were statistically comparable with the two-step MPN technique for the enumeration of E. coli in chlorinated waste-water (4). Fast recovery of faecal coliforms from shell fish (5) and sea water (6) was also reported. A-1 Medium also conforms to the standard methods identified for the isolation of faecal coliforms in food, water and wastewater (2,7).
Casein enzymic hydrolysate provides carbonaceous and nitrogenous substances required for bacterial metabolism. Lactose and salicin act as energy sources and sodium chloride maintains osmotic equilibrium. Polyethylene glycol p-isooctylphenyl ether acts as a surfactant. Presence of gas bubbles in the inverted Durhams tubes is a positive indication of presence of faecal coliforms. The density of faecal coliform can be calculated by the standard methods using the MPN table.
Quality Control
Appearance
Cream to yellow coloured granular medium
Colour and Clarity of prepared medium
Light amber coloured clear solution after cooling to room temperature.
Reaction
Reaction of 3.15% w/v aqueous solution at 25°C. pH : 6.9±0.1
pH
6.80-7.00
Cultural Response
Cultural characteristics observed after an incubation at different temperatures for 18-24 hours.
Cultural Response
| Organism | Inoculum (CFU) | Growth at 35°C | Growth at 44.5°C |
|---|---|---|---|
| Cultural Response | |||
| Bacillus subtilis ATCC 6633 | 50-100 | none | none |
| Enterobacter aerogenes ATCC 13048 | 50-100 | luxuriant (may or may not produce gas) | poor-fair |
| Escherichia coli ATCC 25922 | 50-100 | luxuriant with gas | luxuriant with gas |
| Salmonella Typhimurium ATCC 14028 | 50-100 | luxuriant without gas | good without gas |
| Enterococcus faecalis ATCC 19433 | 50-100 | poor | none - poor |
Storage and Shelf Life
Store below 30°C in tightly closed container and the prepared medium at 2-8°C. Use before expiry date on the label.
| Product Name | A-1 Broth, Granulated |
|---|---|
| SKU | GM874 |
| Product Type | Granulated |
| Physical Form | Granular |
| Origin | Animal |
| Packaging type | HDPE |
| References | 1. Andrews and Presnell, 1972, Appl. Microbiol., 23:521.2.Baird R.B., Eaton A.D., and Rice E.W., (Eds.), 2015, Standard Methods for the Examination of Water andWastewater, 23rd ed., APHA, Washington, D.C. |
| Customized Product Available | No |
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