Biology – Antibiotics | e-Consult

Antibiotic resistance arises through the process of natural selection. Bacteria, like all living organisms, exhibit genetic variation. Some bacteria within a population may possess genes that confer resistance to antibiotics, either through mutations or by acquiring resistance genes from other bacteria. When antibiotics are used, the susceptible bacteria are killed or inhibited, while the resistant bacteria survive and reproduce. This leads to an increase in the proportion of resistant bacteria in the population over time.

Here are some examples of how natural selection drives antibiotic resistance:

• Mutations: Random mutations in bacterial DNA can sometimes result in genes that provide resistance to specific antibiotics. For example, a mutation in a gene encoding a bacterial cell wall protein might alter the structure in a way that prevents the antibiotic from binding effectively.
• Horizontal Gene Transfer: Bacteria can acquire resistance genes from other bacteria through horizontal gene transfer mechanisms. These mechanisms include:

  • Conjugation: Transfer of plasmids (small, circular DNA molecules) containing resistance genes between bacteria through direct contact.
  • Transformation: Uptake of free DNA containing resistance genes from the environment.
  • Transduction: Transfer of resistance genes by bacteriophages (viruses that infect bacteria).

• Selective Pressure: The use of antibiotics creates a strong selective pressure favoring the survival and reproduction of resistant bacteria. The more antibiotics are used, the greater the selective pressure, and the faster resistance develops.
• Biofilms: Bacteria growing in biofilms are often more resistant to antibiotics than planktonic (free-floating) bacteria. Biofilms protect bacteria from antibiotics by forming a physical barrier and reducing antibiotic penetration.

The continuous use of antibiotics provides a constant selective pressure, driving the evolution and spread of antibiotic-resistant bacteria. This highlights the importance of antibiotic stewardship and the development of new strategies to combat resistance.