IB DP Biology: SL复习笔记6.3.5 Antibiotic Resistance

• Within a bacterial population, there is variation caused by mutations (as occurs in populations of all species)
• A chance mutation might cause some bacteria to become resistant to an antibiotic (eg. penicillin)
• When the population is treated with this antibiotic, the resistant bacteria do not die
• This means the resistant bacteria can continue to reproduce with less competition from the non-resistant bacteria, which are now dead
• Therefore the genes for antibiotic resistance are passed on with a much greater frequency to the next generation
  • As bacteria only have one copy of each gene, a mutant gene will have an immediate effect on any bacterium possessing it
• Over time, the whole population of bacteria becomes antibiotic-resistant because the antibiotic-resistant bacteria are best suited to their environment
• This is an example of evolution by natural selection
• Some pathogenic bacteria have become resistant to penicillin as they have acquired genes that code for the production of the enzyme β-lactamase (also known as penicillinase), which breaks down penicillin

Bacteria evolve rapidly as they reproduce quickly and acquire random mutations – some of which confer resistance

The future of antibiotic resistance

• Antibiotic-resistant strains are a major problem in human medicine
• New resistant strains are constantly emerging due to the overuse of antibiotics
  • By using antibiotics frequently, humans exert a selective pressure on the bacteria, which supports the evolution of antibiotic resistance
• Scientists are trying hard to find new antibiotics that bacteria have not yet been exposed to, but this process is expensive and time-consuming
• Some strains of bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), can be resistant to multiple antibiotics and they create infections and diseases which are very difficult to treat
• When antibiotics were discovered, scientists thought they would be able to eradicate bacterial infections, but less than a century later a future is being imagined where many bacterial infections cannot be treated with current medicines

Measures to avoid antibiotic resistance

• Antibiotic resistance in bacteria is an example of natural selection that humans have helped to develop through incorrect use or overuse of antibiotics
• Implementation of certain measures can help to avoid antibiotic resistance. These measures may include:
  • Avoiding prescription of antibiotics for non-serious or non-bacterial infections
  • Completing the full prescribed course of antibiotics to ensure the infection is completely cleared
  • Maintaining high standards of hygiene in the hospital environment
  • Minimising use of antibiotics for routine treatment to animals in agriculture
  • Development of new types of antibiotic