What Are Bacterial Pathogens?

Pathogens refer to microorganisms (including bacteria, viruses, rickettsia, fungi), parasites or other vectors (recombinant microorganisms include hybrids or mutants) that can cause diseases in humans or animals and plants.

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Pathogens are those that can cause diseases in humans, animals and plants.

Pathogen A collective term for microorganisms and parasites that can cause disease.

To determine which level of biological safety a pathogen belongs to is based on experimental manipulations. The manipulation of pathogens is usually related to the growth of the pathogens required for identification or typing, and the number and concentration of the pathogens. If operating clinical samples poses less risk to staff than operating culture samples, it is recommended to determine a lower level of biosafety. On the other hand, if the experimental procedure involves a larger sample and / or a higher concentration ("production quantity") of the pathogen preparation, or aerosol may be generated, or the operation itself is dangerous, additional precautions are required , And improve the level of primary and secondary non-proliferation devices.

Although it is slower and more complicated than the direct inspection method, it is more accurate and has a wider range of applications. It can be used for almost all pathogens. In addition to viruses, chlamydia and rickettsials, they can be cultured and isolated in inanimate media. There are many types of culture media, which can be selected according to different pathogens. After cultivation and isolation of pathogens, various tests, such as fermentation tests and virulence tests, can be performed, which is very important for the further identification of pathogens. Viruses, chlamydia, and rickettsia lack the various enzymes necessary to sustain life. They cannot ingest nutrients from the culture medium like bacteria. They use their own enzymes to synthesize various components they need. They cannot use inanimate The medium is cultured, and it must be inoculated into a living organism, using the enzymes of the organism to synthesize various components they need. This method is called "virus isolation," "chlamydia isolation," or "rickettsia isolation."

There are generally three methods of separation:

Tissue culture. The simplest and most commonly used;

Vaccination of animal embryos (such as chicken embryos and duck embryos);

Vaccination of animals, such as mice, guinea pigs, etc. Different viruses, chlamydia, or rickettsia often require different methods of separation. After a positive separation, various tests (such as serological tests) are often required to determine the type. Direct inspection of pathogens is often performed simultaneously with the isolation of the pathogens.

In addition to the above two methods, there are some special inspection methods. For example, for suspected humans or animals, the brain tissue can be taken to check the specific inclusion body (Negris body); the hepatitis B surface antigen can be tested using reverse passive hemagglutination (RPHA) enzyme-linked immunosorbent assay (ELISA) ) And radioimmunoassay (RIA) and other methods; immunoelectron microscopy can be used to check hepatitis A virus in stool. Molecular hybridization or nucleic acid analysis can also be used to detect pathogenic nucleic acids in patients' blood, tissues or feces to assist diagnosis. For example, hepatitis B virus nucleic acids in blood and liver tissue can be detected by molecular hybridization; stool Rotavirus can be detected by nucleic acid analysis. As various antigens of pathogens and nucleic acids of pathogens are specific components of pathogens, if they appear positive, they are also positive for pathogens, so these methods also have great diagnostic significance.