The agricultural use of antibiotics should be restricted.

The idea

Antibiotics are used in farming to treat and sometimes to prevent disease in livestock, and low doses have historically been added to feed to promote growth. This creates frequent exposure of large numbers of bacteria to antibiotics, increasing the chance that resistant mutants survive and reproduce. Resistance genes can then spread between bacteria, including from farm animals to humans through food, water, direct contact or the environment. Restricting agricultural use means antibiotics are given only when medically necessary, at appropriate doses, and not routinely for growth promotion. This reduces the selection pressure that favours resistant bacteria, helping to keep antibiotics effective for treating human infections.

For example: Limiting routine preventive dosing in poultry can lower the number of resistant bacteria entering the food chain.

What earns the marks

• Antibiotics are used in agriculture to treat disease, prevent disease and sometimes to promote growth in livestock.
• Frequent or low-dose use exposes many bacteria to antibiotics and increases selection pressure.
• Resistant bacteria selected in animals can spread to humans through food, water, contact or the environment.
• Restricting use to necessary treatment reduces the number of bacteria exposed and slows the development of resistance.
• Resistance genes can be transferred between bacteria, so reducing agricultural use can limit the spread of resistance.
• Responsible use in agriculture helps preserve the effectiveness of antibiotics for treating human infections.

Common mistakes and how to put them right

• Thinking that agricultural restriction means animals cannot be treated for illness.

  Put it right: Antibiotics should still be used when an animal is genuinely ill, but not routinely or for growth promotion.

• Believing that resistance in farm animals cannot affect humans.

  Put it right: Resistant bacteria and resistance genes can reach humans through food, water and contact.

• Assuming that only human medicine causes resistance.

  Put it right: Any use of antibiotics, including in farming, can select for resistant bacteria.

Exam tips

• Name specific routes by which resistant bacteria can pass from farm animals to humans.
• Use the phrase selection pressure when explaining why routine agricultural use increases resistance.
• When evaluating a restriction, give one benefit and one cost, then state a supported conclusion.