Question

Antibiotics are not effective for viral diseases. Give reasons.

Answer 1

Hint: Some micro-organisms (penicillium notatum) secrete certain chemicals that inhibit the growth of other microbes (bacteria) around it.

Complete answer:
Antibiotics are not effective against viruses because they cannot inhibit viruses as bacteria and viruses have different strategies and machinery to survive and replicate. The antibiotic has no substrate to bind to in a virus.
An antibiotic is a kind of antimicrobial drug active mainly against bacteria. It is derived from living matter or micro-organism and has a 'cidal' or 'static' action. It is therefore used to kill or prevent the growth of other microorganisms like bacteria but not viruses. Some of the antibiotics also confer antiprotozoal activity. Viruses are structurally different from bacteria. Viruses require a host to sustain life and replicate as they cannot live outside of this environment. Viruses insert their genetic material into a human cell’s DNA in order to reproduce its genetic material and acquire its lipid component from the host's cell wall.

Reasons due to which viral disease is not treated by antibiotics are as follows-
- The virus is devoid of a cell wall.
- The virus has no replicating machinery of its own. It takes control of the host genetic material and uses it for the production of virus particles.
- Antibiotics are unable to inhibit the Reverse Transcriptase enzyme present in the viruses through which they convert their RNA into DNA.

Additional Information:
Antibiotics kill bacteria mainly through five mechanisms, they are-
- Inhibition of cell wall synthesis (the most common mechanism).
- Inhibition of protein synthesis (Translation)
- Alteration of cell membranes.
- Inhibition of nucleic acid synthesis.
- Antimetabolite activity.

Note: Viral diseases are treated by a set of drugs known as Antiviral drugs. They can be NRTIs (Nucleoside Reverse Transcriptase Inhibitors), NNRTI (Non-Nucleoside Reverse Transcriptase Inhibitor), protease inhibitors, DNA gyrase inhibitors, etc.