It is necessary to ensure the quality of the culture medium plate
Nowadays, with the rapid development of science and technology, the high-tech methods of microbial detection can be described as vast. Although the detection of microorganisms in petri dishes is an ancient and traditional detection method, it is still widely used in medicine and health, clinical testing, laboratory animals, food, cosmetics, industry and agriculture, environmental protection and many other fields because of its advantages such as direct separation and identification of samples, convenient operation and reliable results. It plays an important role in drug quality control, safety evaluation and disease diagnosis.
The culture medium is the basis for microbial testing and directly affects the results of microbial testing. The finished pre-loaded culture medium plate is one of the culture mediadehydrated mediumCompletely dissolved in water, corrected pH, then sterilized and sub-packaged in flat dishes. Whether it is a laboratory-prepared medium flat dish or a commercialized finished pre-packaged medium flat dish, its quality depends on the entire process of its preparation. Media prepared by inappropriate methods will affect the growth or recovery of microorganisms, thus affecting the reliability of test results. So to ensure the quality of the medium flat dish, special attention should be paid to the following matters:
1
Select the appropriate medium preparation method, and do not use agglomerated or color-altered dehydrated medium.
2
Sterilization of media should be carried out according to the parameters provided by the manufacturer or verified to avoid the use of inappropriate heating and sterilization conditions, which can cause changes in medium color, transparency, agar coagulation power, or pH.
3
The pH value of each batch of medium should be determined after sterilization (measured by cooling to room temperature at 25 ° C). If the pH range is not listed in the medium prescription, unless it is verified that the pH range of the medium is allowed to vary widely, the pH range should not exceed the specified value ± 0.2.
4
The finished pre-packaged culture medium plate should be kept sterile, and the plate should not be broken, to avoid the formation of bubbles, cracks or ripples on the surface of the solid culture medium should not be formed, crystals should not be formed at the refrigeration temperature, and microorganisms should not be contaminated.
5
The temperature rises slowly during the heating and sterilization process of the medium or cools down too slowly after sterilization, which may lead to overheating or over-sterilization of the medium, which will reduce the quality of microbial medium growth to a certain extent. Therefore, the finished pre-packaged medium flat dish should be passedmicroorganismThe growth promotion test was verified.
6
Plates used for environmental monitoring must be specially protected, preferably in three-layer packaging and sterilized at the end point. It is not recommended to use laboratory-made petri dishes for sampling in clean area environments after 100% pre-culture, because water loss during pre-culture can affect microbial growth and there is also the possibility of petri dishes being contaminated.
7
Storage and transportation conditions should minimize moisture loss and provide mechanical protection from light. Plates containing agar media should not be stored at or below 0 ° C. Freezing may damage gel properties.
The quality control and storage conditions of the preparation process of the culture medium flat plate are the guarantee of providing high-quality medium. The medium for monitoring planktonic bacteria, sedimentary bacteria and surface microorganisms in clean areas generally uses pancreatic casein soybean peptone agar medium (TSA), and appropriate neutralizing agents can be added when necessary; when the monitoring results are suspected of fungi or considering seasonal factors, the saxophone agar medium (SDA) can be added.
