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An Overview of Detection Methods for Antibiotics in Milk

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  1. Types of antibiotics in milk
  2. a. β-lactams

β-lactams include penicillins and cephalosporins, which are often used in the clinical treatment of dairy cattle and other livestock individuals and are left in the milk.

  1. Tetracyclines

Common types of Tetracyclines have tetracycline, chlortetracycline, oxytetracycline, doxycycline, etc., which is a class of broad-spectrum antibiotics.

  1. Aminoglycosides

Common types of Aminoglycosides include gentamicin, streptomycin, dihydrostreptomycin, neomycin, spectinomycin, etc., which are aminoglycoside antibiotics commonly used in livestock.

  1. Chloramphenicol

Chloramphenicol includes the following three compounds: chloramphenicol, thiamphenicol, and florfenicol. These drugs are strictly restricted veterinary drugs, and some countries prohibit their use.

  1. Macrolides

Common types of Macrolides are erythromycin, gentamicin, lincomycin, spiramycin and salinomycin.

  1. Sulfa

Common types of Sulfa are sulfadiazine, sulfadimethoxine, sulfadiazine, sulfadiazine, etc. Trimethoprim is a sulfamethoxin synergist and is not used alone.

  1. The hazards of antibiotic residues

Antibiotic residues have different degrees of harm to human health, ecological balance, dairy product prices and international trade in dairy products.

  1. The detection method of antibiotics in milk

1). Traditional microbiological testing method

The microbiological detection method appeared earlier. Since its appearance, it has greatly improved the development of antibiotic detection methods. Its measurement principle is based on the antibiotics have a certain inhibitory effect on the physiological function and metabolism of microorganisms, which is consistent with clinical applications. It takes a long time and has a large rate of error. At present, the most commonly used methods are TTC method, Delvotest SP method, BY method, etc.

2). Internationally accepted testing methods

Relatively speaking, it is an earlier universal measurement method applied in the world. Its principle is: if the milk contains antibiotics, add bacteria (Streptococcus thermophilus) and cultivate for 2.5-3h, adding the TTC indicator (triphenyltetrazolium) does not cause a reduction reaction, so the sample is colorless. If the milk contains no antibiotics, the sample is red. Relatively speaking, this method is relatively low-cost, but time-consuming, so its application is not too wide, and its development is subject to certain restrictions.

3). Blue and yellow detection method

This method is a broad-spectrum microbial inhibition method, relatively speaking, it takes a short time, you can check the residue of antibiotics in a short time, as long as you can draw a conclusion by color comparison. As a result, there is a certain error rate for the detection obtained by this detection method, which is easy to cause false detection, but it is short in time and low in cost.

4). Modern instrumental analysis

This method mainly uses modern instruments to detect and determine the type of antibiotics remaining. The most commonly used methods are chromatography, fluorescence, capillary electrophoresis, and chromatography-mass spectrometry. Use different theories and adopt different methods for testing, improve the standard of testing, and strengthen the quality of testing. Relatively speaking, this method has a fast separation speed, high efficiency, and automatic control. It can detect the specific content of antibiotics, and the results are more accurate. However, the sample to be tested needs a series of pretreatments, which is tedious and time-consuming, and must have the corresponding price. It is generally used in large laboratories, suitable for accurate determination.

5). Biochemical Immunity

This has been gradually developed in recent years with the development of new technologies. It combines the specificity and reversibility of antigens and antibodies, and is an analytical technique. The basic principle is the competitive combination of antigens, which can be divided into enzyme-linked immunoassay (ELISA), fluorescent immunoassay (FIA), immunoassay technology and conventional physical and chemical analysis technology combined methods. Several methods have their own advantages and disadvantages, and we must pay attention to their comprehensive use to improve the quality and accuracy of detection. Judging from the results of its practice, it has a good detection effect on the current status of antibiotic residues, and its sensitivity is extremely high, reaching the level of ng; the detection is fast and specific. Relatively speaking, this method has a high degree of specificity, and each time an antibiotic is tested, a corresponding antigen or antibody must be prepared or purchased, resulting in a higher test cost. Therefore, the biochemical immunoassay cannot replace conventional analytical methods such as chromatography or spectroscopy, and can only serve as an important supplement.

6). Specific kits

The so-called special kit method is based on the culture of agar medium containing Bacillus and PH indicator at a certain temperature, generally maintained at about 65 celsius, spore development and growth, reduce the pH value of the medium; under the action, the blue (purple) color becomes green-yellow. Antibiotic residues in raw milk inhibit the growth of microorganisms and the production of acids. Since no acid is produced, the color will not change.

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