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Pathogens , in medicine as germ called, are micro-organisms or subcellular pathogens that cause harmful in other organisms procedures. Pathogens can be algae , bacteria , parasites , fungi , prions , protists , viruses or viroids . Infection with a pathogen is called infection , and infestation with a parasite is called infestation .

The term pathogen is often used synonymously, but has a more general meaning, similar to the adjective pathogen . Harmful substances ( poisons ) and ionizing radiation can also be referred to as pathogens in the sense of "disease triggers".


The harmful effects of microorganisms are based on three mechanisms:

  • They damage the tissue through phagocytosis , i.e. that is, they feed on body cells.
  • They cause a very violent immune reaction , especially a high fever, which can be fatal.
  • They actively secrete substances that harm the body, or they contain such; these are released when the microorganism dies.

Bacteria damage the infected organism by secreting toxins (poisonous substances):

According to the Biological Agents Ordinance , pathogens are divided into four risk groups based on their danger to humans .

Subcellular pathogens

Subcellular pathogens are obligatory intracellular parasites. They differ from normal poisons in that they are in host cells by replication reproduce; or in the case of prions by transferring their structure to other prions.

Pathogenic viruses

Pathogenic viruses couple to surface molecules of the host cells and smuggle their genetic material into them. This penetrates into the cell nucleus and changes the cell's own DNA. There is a u. U. massive replication of the virus body (genome and proteins) in the affected cell by the cell organelles present.


Viroids consist exclusively of a single, ring-shaped strand of ribonucleic acid (RNA).


In the case of virusoids, packaging and release are dependent on the presence of a helper virus in the same infected cell.

Satellite viruses

Satellites are subviral particles made up of a nucleic acid molecule and some proteins. They can be viewed as dependent viruses that are not able to multiply in a host cell on their own. For their replication they also need one or even several helper viruses , with which the host cell must be infected at the same time ( co-infection ). The helper virus provides the functions required for the satellite to multiply. The host cell then mainly produces the satellite instead of the virus.

Pathogenic prions

Prions are proteins with an alpha-helix and beta-sheet tertiary structure which, like enzymes , change the tertiary structure of other proteins. This is repeated, that is, the modified proteins become pathogenic prions themselves and convert other proteins into prions.

See also


  • Rüdiger Meyer: "Emerging Infections". Dangers from new and old pathogens. In: Deutsches Ärzteblatt. 97, No. 25, ISSN  0176-3989 , 2000, pp. A1736-A1740 ( online text version ).

Web links

Wiktionary: Pathogens  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. For example, the Infection Protection Act defines pathogens in Section 2 Definitions as "a reproductive agent (virus, bacterium, fungus, parasite) or another biological transmissible agent that can cause an infection or communicable disease in humans" (underlining added).
  2. ^ DocCheck Flexikon: Pathogen
  3. See Duden online: pathogen
  4. Helmut Hahn, Stefan HE Kaufmann, Thomas F. Schulz, Sebastian Suerbaum (eds.): Medical microbiology and infectious diseases . 6th edition. Springer Verlag, Heidelberg 2009, ISBN 978-3-540-46359-7 .