How are infectious agents classified?
Based on the common characteristics shared, microorganisms are classified into major groups. They are:
- Viruses
- Bacteria
- Fungi
- Single-celled animals or Protozoans
- Multicellular helminths
Let us now look at an example of diseases caused by the respective groups of microbes.
| Sr. No | Group of Microbes | Disease caused |
| 1. | Virus | Common cold |
| 2. | Bacteria | Diarrhoea |
| 3. | Fungi | Skin rashes |
| 4. | Single-celled animals or Protozoans | Malaria |
| 5. | Multicellular helminths | Intestinal infections |
What are the advantages of classifying infectious agents?
These categories are important factors in deciding what kind of treatment to use. Members of each one of these groups have many biological characteristics in common. Medicine that block one of these life processes in one member of the group is likely to be effective against many other members of the group. But the same drug will not work against a microbe belonging to a different group.
Let us understand this with the help of an example.
Antibiotics commonly block biochemical pathways important for bacteria. For example, Many bacteria, make a cell-wall to protect themselves. The antibiotic ‘penicillin’ blocks the bacterial processes that build the cell-wall. As a result, growing bacteria become unable to make cell-walls and die easily. Thus, penicillin will target those bacteria which make cell-wall to protect themselves.
Thus, an antibiotic working against one bacteria is likely to work against other similar bacteria as well.