Antibiotic residue status and detection methods

With the rapid development of China's economy, people are pursuing maximum benefits, and the use of antibiotics is becoming more and more common. For example, antibiotics are used to treat mastitis in dairy cows; Appetite; aquaculture users feed crabs with a large amount of antibiotics and hormones in order to speed up the shelling process of crabs and make them fat and fertile. China is a major country in the production and use of antibiotics. According to statistics, about 6,000 tons of antibiotics are used for feed additives each year, accounting for 50% of the global antibiotic feed additives.

The massive abuse of antibiotics has seriously threatened people's health. Experts pointed out that regular consumption of foods containing antibiotics, even in trace amounts, can cause urticaria or cause anaphylactic shock. Frequent intake of foods containing antibiotics can make certain strains resistant, resulting in difficulties in preventing and treating certain human and animal diseases. Long-term consumption of foods left by antibiotics can cause the death of some non-pathogenic bacteria in the human body, make the microflora imbalance or cause riboflavin deficiency and purpura damage. Especially the abuse of chloramphenicol is very easy to damage the hematopoietic function of human bone marrow and thus lead to the occurrence of aplastic anemia. Two years ago, there was an outbreak of Streptococcus suis in Ziyang, Sichuan. Microbiology expert Professor Li Mingyuan believed that it may be caused by the long-term abuse of antibiotics in pig feed by farmers.

Commonly used antibiotics include β-lactams, tetracyclines, aminoglycosides, macrolides, sulfonamides, etc. Countries around the world put forward strict standards on the amount of antibiotics used. The EU standards are more stringent than those of Japan and the United States. The limit value is lower. If our country wants to guarantee the food safety of our country and export products to the above countries, we must strengthen our own testing capabilities.

In general, meat (livestock), fish and shrimp (aquatic products), eggs, milk, feed, honey and other products need to be tested for antibiotics. Common methods include: liquid chromatography or liquid chromatography coupled with mass spectrometry, microorganisms Inhibition method and enzyme-linked immunoassay method.

Chromatography is a physical and chemical detection method. It usually goes through the steps of sample extraction, deproteinization, centrifugation, chromatographic column purification, and derivatization. It can detect the specific content of antibiotics and has high sensitivity, but the detection procedure is complicated and the cost is relatively high. High, need to buy chromatograph and other testing equipment, not suitable for small laboratory.

The microbiological inhibition method and the enzyme-linked immunoassay method are screening methods, which are easy and fast to operate, and have low consumption costs. There is no need to purchase large-scale instruments, but positive results need to be confirmed by other methods. There are certain false positives in the enzyme-linked immunoassay method, and the microbial method will be described in detail below.

The microbial inhibition method includes three types:

1. Inhibition circle analysis method: A circular paper sheet with a certain antibiotic concentration is placed on a plate medium evenly inoculated, and a certain size of inhibition zone will be produced around the antibiotic paper sheet. The diameter of the bacteriostatic circle can be used to obtain the concentration of antibiotics to be tested. It is generally suitable for animal-derived foods such as meat, fish, shrimp and eggs. Liofilchem ​​company can currently provide up to 150 kinds of antibiotic paper, the concentration meets the requirements of EUCAST, CLSI, BSAC standards.

2. The Bacillus stearothermophilus inhibition medium is pre-mixed with Bacillus stearothermophilus spores and contains a pH indicator (bromocresol purple). After adding the sample and incubating, if the sample does not contain antibiotics or the antibiotic concentration is below the detection limit, bacterial spores will grow in the medium and use sugar to produce acid, and the purple color of the pH indicator will turn yellow. On the contrary, if the sample contains antibiotics higher than the detection limit, the bacterial spores will not grow, the color of the pH indicator remains unchanged, and it is still purple. It is mainly used for the detection of antibiotics in dairy products and macrolides in animal-derived samples Category detection. Liofilchem's MiRA Test and MeRA Test products are mainly used for the detection of antibiotics in dairy products and meat samples. They can detect 34 and 29 antibiotics, respectively, and the minimum detection limit complies with EU standards.

3. After the sterilization of the Streptococcus thermophilus sample is sterilized at 80 ° C, add the Streptococcus thermophilus bacterial solution. After a period of cultivation, Streptococcus thermophilus begins to proliferate. At this time, the metabolic substrate 2,3,5-triphenyltetrazolium chloride (TTC) is added. If the sample does not contain antibiotics or the concentration of antibiotics is below the detection limit, Streptococcus thermophilus will continue to multiply, reducing TTC to become Red substance. Conversely, if the sample contains a bacteriostatic agent above the detection limit, Streptococcus thermophilus is inhibited, so the indicator TTC is not reduced and maintains the original color.

The emergence of antibiotics was a great feat for human beings. It saved the lives of countless people and created great economic benefits. However, because some people lacked relevant knowledge and were driven by interests, the abuse of antibiotics caused serious harm to the human body and the environment. . It is hoped that the national inspection department can resolutely enforce the law and protect the people's health.