Dehydrated culture media
APT Agar (All Purpose Tween)
For enumeration and cultivation of heterofermentative lactic acid bacteria including lactobacilli, Leuconostocs and lactic acid streptococci.
- Cat. No.
- LC-2049
- Category
- Dehydrated culture media
- Format
- 500 g
- Storage
- 2 to 25 °C
- Minimum guaranteed shelf life
- 15 months
APT Agar was formulated by Deibel, Evans and Niven when they were investigating thiamine-requiring bacteria and heterofermentative lactobacilli. Lactobacillus forms a major part of the lactic acid bacteria group, which are abundant in nature. They convert lactose and other sugars to lactic acid and therefore are named as Lactobacillus. This medium is recommended for the microbiological examination of canned meat, poultry, sauerkraut and other food. APT Agar is also used in the microbiological assay of thiamine.
Key features
Applications
Selective enumeration of lactic acid bacteria.
Industry
Food.
Preparation
59.5 g in 1 liter of distilled water with 0.1 g of cycloheximide and 0.2 mL of Tween 80; boil for one minute, sterilize in autoclave at 121 °C for 15 minutes.
Principles and uses
APT Agar contains peptone mixture, which acts as a source of carbon, nitrogen, vitamins and minerals. Yeast extract provides vitamin and B-complex nutrients, which are required for the growth of bacteria. Dextrose is the carbohydrate source. Manganese chloride, magnesium sulphate and ferrous sulphate are essential for the replication of lactobacilli and lactic acid streptococci. Polysorbate 80 is a source of fatty acids required by lactobacilli. Sodium citrate partially inhibits the growth of Gram-negative bacteria.
Technical specifications
| Solubility | Without residues |
|---|---|
| Appearance | Fine powder |
| Color of the dehydrated medium | Beige |
| Color of the prepared medium | Amber, slightly opalescent |
| Final pH (25 °C) | 6.7 ± 0.2 |
| Amount per litre | 59.5 g |
| Storage | 2 to 25 °C |
Formula
| Ingredient | g/L |
|---|---|
| Bacteriological agar | 13.5 |
| D(+) Glucose | 10 |
| Ferrous sulfate | 0.004 |
| Magnesium sulfate | 0.8 |
| Manganese (II) chloride | 0.14 |
| Peptone | 12.5 |
| Sodium chloride | 5 |
| Sodium citrate | 5 |
| Thiamine hydrochloride | 0.001 |
| Yeast extract | 7.5 |
| Potassium hydrogen phosphate | 5 |
Typical formula in g/L, adjusted and/or supplemented as required to meet performance criteria.
Preparation and use
Preparation
Suspend 59.5 grams of the medium in 1 liter of distilled water. Add 0.1 grams of cycloheximide dissolved in a minimum amount of 40% ethanol, and 0.2 mL Tween 80. Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. Sterilize by autoclaving at 121 °C for 15 minutes.
Instructions for use
For enumeration:
- Dilute the sample material and inoculate the APT Agar by the pour-plate method.
- Incubate for 1-2 days at 35 °C aerobically.
For identification:
- Inoculate with the suspect colonies to identify the bacteria that cause greening of meat products. Transfer a sample from the culture onto the cut surface of a smoked sausage.
- Place the sausage in a Petri dish containing a wet piece of filter paper ("moist chamber").
- Incubate for 18-24 hours at 32 °C and observe if there is a green coloration.
- A sample of the sausage which has not been inoculated serves as a control.
- In order to exclude other pigment-forming bacteria (e.g. Pseudomonas), a verifying test (e.g. Gram-positive test, negative catalase test, negative nitratase test, positive peroxidase test, acetoin production from glucose, ammonia production from arginine, etc.) should be performed.
Quality control
Microbiological test
Incubation conditions: 35 °C / 18-24 h.
| Microorganism | Specification |
|---|---|
| Lactococcus lactis ssp. lactisATCC 19435 | Good growth |
| Lacticaseibacillus caseiATCC 393 | Good growth |
| Lactobacillus acidophilusATCC 4356 | Good growth |
| Lactiplantibacillus plantarumATCC 8014 | Good growth |
| Lactobacillus fermentumATCC 9338 | Good growth |
| Lactobacillus rhamnosusATCC 9595 | Good growth |
Bibliography
- Evans and Niven, 1951, J. Bact., 62:599.
- Downes F. P. and Ito K. (Eds.), 2001, Compendium of Methods for the Microbiological Examination of Foods, 4th ed., APHA, Washington D.C.
- J.B. Evans and C.F. Niven, Nutrition of the heterofermentative Lactobacilli that cause greening of cured meat products, J. Bact., 62, 599 (1951)
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