Why Don't Antibiotics Work on Viruses?

Key Concepts

• Antibiotics and Their Function:
  • Antibiotics can:
    • Block transcription
    • Block translation
    • Prevent DNA replication
    • Prevent cell wall synthesis
    • Stop metabolic reactions using enzymes
• Structure of Viruses:
  • Viruses typically have:
    • A protein coat known as a capsid
    • Nucleic acid (either DNA or RNA, never both)

Why Antibiotics are Ineffective Against Viruses

• Lack of Target Sites:
  • Viruses lack structures and processes that antibiotics target in bacteria.
  • Example:
    • Penicillin prevents cell wall synthesis but viruses do not have a peptidoglycan cell wall.
    • Viruses do not carry out their own transcription or translation.
    • Viruses do not have the enzymes that antibiotics target.

Handling Viral Infections

• Medications:
  • Though there is no "cure" for the common cold:
    • Symptomatic treatments exist (e.g., fever reducers).
    • Antivirals exist for some viruses like herpes.
    • Anti-retrovirals for viruses like HIV.
• Immune System:
  • Plays a crucial role in combating viruses.
  • Further discussion in Chapter 11 on the immune system.

Exam Tips

• If asked why antibiotics do not work on viruses, state:
  • "Viruses lack target sites affected by antibiotics."
  • Use examples like the lack of a peptidoglycan cell wall in viruses.

Conclusion

• Antibiotics are ineffective against viruses due to structural and functional differences compared to bacteria.
• There are treatments to manage symptoms and certain antiviral drugs for specific viruses.