CIE A Level Biology (9700) 2019-2021

Revision Notes

10.2.3 Consequences of Antibiotic Resistance

Consequences of Antibiotic Resistance

Consequences of antibiotic resistance

  • Commonly prescribed antibiotics are becoming less effective for many reasons, the main being:
    • Overuse of antibiotics and antibiotics being prescribed when not necessary
    • Large scale use of antibiotics in farming to prevent disease when livestock are kept in close quarters, even when animals are not sick
    • Patients failing to complete the full course of antibiotics prescribed by doctors
  • These factors have led to a reduction in the effectiveness of antibiotics, and an increase in the incidence of antibiotic resistance
  • These bacteria are commonly known as superbugs
  • The most common example is a strain of Staphylococcus aureus that has developed resistance to a powerful antibiotic methicillin and is now known as MRSA (Methicillin-resistant Staphylococcus aureus) as well as other antibiotics (eg. penicillin)
  • Bacteria living where there is a widespread use of many different antibiotics may have plasmids containing resistance genes for several different antibiotics, giving them multiple resistance and presenting a significant problem for doctors
  • In addition, resistance may first appear in a non-pathogenic bacterium, but then be passed on to a pathogenic species by horizontal transmission
  • There is a constant race to find new antibiotics as resistant strains are continuously evolving

Reducing antibiotic resistance & its impact

  • Ways to prevent the incidence of antibiotic resistance increasing include:
    • Tighter controls in countries in which antibiotics are sold without a doctor’s prescription
    • Doctors avoiding the overuse of antibiotics, prescribing them only when needed (patients must only be given antibiotics when absolutely essential) – doctors should test the bacteria first to make sure that they prescribe the correct antibiotic
    • Antibiotics not being used in non-serious infections that the immune system will ‘clear up’ (patients must not keep unused antibiotics for self-medication of such non-serious infections in the future)
    • When prescribed a course of antibiotics, the patient finishing the entire course (even if they feel better after a few days) so that all the bacteria are killed, and none are left to mutate to become resistant strains
    • Antibiotics not being used for viral infections (antibiotics have no effect on viruses anyway, and this just provides an unnecessary chance for bacteria to develop resistance)
    • The use of ‘wide-spectrum’ antibiotics being reduced and instead those antibiotics that are highly specific to the infection (‘narrow-spectrum’ antibiotics) being used
    • The type of antibiotics prescribed being changed so that the same antibiotic is not always prescribed for the same infections and diseases (this reduces the chance of a resistant strain developing)
    • The use of antibiotics being reduced and more tightly controlled in industries such as agriculture – controls are now in place to limit their use in farming, where antibiotics are used to prevent, rather than cure, bacterial infections
  • The spread of already-resistant strains can be limited by:
    • Ensuring good hygiene practices such as handwashing and the use of hand sanitisers (this has reduced the rates of resistant strains of bacteria, such as MRSA, in hospitals)
    • Isolating infected patients to prevent the spread of resistant strains, in particular in surgical wards where MRSA can infect surgical wounds


Alistair graduated from Oxford University in 2014 with a degree in Biological Sciences. He has taught GCSE/IGCSE Biology, as well as Biology and Environmental Systems & Societies for the International Baccalaureate Diploma Programme. While teaching in Oxford, Alistair completed his MA Education as Head of Department for Environmental Systems and Societies.

Join Save My Exams

Download all our Revision Notes as PDFs

Try a Free Sample of our revision notes as a printable PDF.

Join Now
Go to Top