Escherichia coli coliform test strip

Escherichia coli coliform test stripSuitable for counting coliforms in food and raw materials, such as detecting samples of disinfected milk, cold drinks, and seasonings, and can also be used for surface hygiene testing.

Escherichia coli coliform test stripIntroduction:

1. Principle and Scope of Application

Escherichia coli and coliform are bacteria that exist in the intestines and feces of warm blooded animals. They are conditionally pathogenic bacteria that mainly cause water pollution and may also lead to food poisoning.Escherichia coli coliform test strip(FilmplateTM E.coli&coliform count plate BE203) is a pre prepared disposable culture medium product, which can simultaneously detect Escherichia coli and coliform group, and contains coliform selective culture medium, cold water soluble absorbent gel, galactosidase (GAL) and glucuronidase (GUD) indicators. Escherichia coli appears blue, while other coliforms appear red. The total number of coliforms is the sum of the blue and red dots.

This product is suitable for counting coliform bacteria in food and raw materials, such as detecting samples of disinfected milk, cold drinks, and seasonings, and can also be used for surface hygiene testing. Execution standard: Microbiological examination of food hygiene - Escherichia coli count - PetrifilmTM test strip method (GB/T 4789.38).

2. Operation method

2.1 Sample processing: Take 25mL (g) of the sample and place it in a sampling tank or homogenization cup containing 225mL of sterile phosphate buffer dilution solution (or physiological saline) to prepare a 1:10 sample homogenate. Use a 1mL sterile pipette to draw 1mL of the 1:10 sample homogenate and inject it into a test tube containing 9mL of dilution solution. Shake to obtain a 1:100 sample homogenate and dilute it downwards in sequence.

2.2 Vaccination: Generally, 1-2 dilutions of food are selected for testing. Liquid samples with low bacterial content (such as drinking pure water and mineral water) can be directly extracted from the original solution for testing. Translate into EnglishEscherichia coli coliform test stripPlace on a flat experimental table, remove the upper layer of the membrane, and use a sterile pipette to slowly and evenly drip 1mL of the sample solution onto a paper sheet. Then slowly cover the upper layer of the membrane and let it stand for about 10 seconds to solidify the culture medium. Inoculate two sheets at each dilution. Simultaneously create a blank negative control.

2.3 Cultivation: Stack the test pieces together and place them back in their original self sealing bags, seal them, and place them horizontally with the transparent side facing up in a constant temperature incubator. The number of stacked pieces should not exceed 12. Cultivate at a temperature of 36 ℃± 1 ℃ for 15-24 hours.

3. Result interpretation

After cultivation, Escherichia coli appears blue, while other coliforms appear red. The total number of coliforms is the sum of the blue and red dots.

4. Counting principles and reporting methods

4.1. Choose paper strips with a colony count between 15 and 150 for counting

4.2. If the bacterial count of both dilutions is between 15 and 150, multiply the average bacterial count by the dilution factor to obtain the number of coliform colony forming units per milliliter (or gram) of sample

4.3. If the bacterial count on all dilution test strips is less than 15, report the average bacterial count on the test strips with lower dilution multiplied by the dilution factor; If there is no bacterial colony growth on all dilution test strips, report it as less than 1 times the low dilution factor

4.4. If the bacterial count of all dilutions is greater than 150, report the average bacterial count on the high dilution test strip multiplied by the dilution factor. When counting test pieces with a colony count greater than 150, the colony count in one or two representative squares can also be counted. After converting to the colony count in a single square and multiplying by 20 (with a filter paper area of 20cm2), the estimated colony count on the test piece is obtained. The reporting unit is expressed in CFU/mL (or CFU/g)

5. Additional explanation

5.1. The pH value of the sample homogenate should be between 6.5 and 7.5, and if necessary, adjust the pH with 1mol/L sodium hydroxide (NaOH) or 1mol/L hydrochloric acid (HCl)

5.2. Most of China's food hygiene standards use coliform as the detection indicator, while many countries such as the European Union use E. coli as the detection object. Therefore, this product has a wider application prospect for export food and aviation catering enterprises

6Escherichia coli coliform test stripStorage conditions

This product needs to be stored in a refrigerator at 4 ℃ to 10 ℃ with a shelf life of one year. After opening the aluminum foil bag, any unused paper should be put back into the aluminum foil bag, sealed, and placed in the refrigerator. It should be used up within one month. Condensation may occur in high humidity environments. Before unpacking, warm the entire package back to room temperature.