How antibiotics work

Antibiotics are drugs that kill or inhibit the growth of bacteria. They target the bacterial enzymes and ribosomes used in metabolic reactions, meaning they do not damage human cells (as they contain different enzymes and ribosomes). 

Examples of how antibiotics affect bacteria include: 

• Preventing the synthesis of bacterial cell walls.
• Disrupting protein activity in the cell membrane.
• Disrupting enzyme action.
• Preventing DNA synthesis.
• Preventing protein synthesis.

Antibiotics do not work against viruses because viruses lack cell structures, instead relying on host cells to carry out metabolic reactions. This means that antibiotics cannot target and disrupt these reactions. Furthermore, antibiotics are unable to reach viruses as they invade the organism's own cells. 

Antibiotic resistance

Following the discovery of penicillin in the mid-20th century, antibiotics have been used to successfully treat numerous bacterial infections. This drastically reduced the number of deaths due to communicable diseases.

However, their increased use has led to the development of antibiotic resistant bacteria. This means that antibiotics that were once effective against these bacteria no longer work, making it much more difficult to treat bacterial infections.

Antibiotic resistance develops via natural selection:

1. Genetic mutations occur, making some bacteria resistant to an antibiotic.
2. When an infection is treated with antibiotics, resistant bacteria are able to survive.
3. Resistant bacteria reproduce, passing on the allele for antibiotic resistance to their offspring.

Genes for antibiotic resistance often occur on plasmids, meaning they can also be transferred from one bacterium to another in the process of conjugation. 

The impact of antibiotic resistance

The development of antibiotic resistant bacteria is a problem because it means that certain bacterial infections are becoming more difficult to treat. 

Some bacteria have developed resistance for several different antibiotics:

• Methicillin-resistant Staphylococcus aureus (MRSA) - These bacteria cause wound infections and are resistant to multiple antibiotics (including methicillin). 
• Clostridium difficile (C. difficile) - These bacteria infect the digestive system and can survive and reproduce in the presence of many antibiotics. 

The following measures can help reduce the development of antibiotic resistance: 

1. Choosing appropriate antibiotics for treatment - Antibiotics can be tested against bacterium strains to make sure they are effective in treating the disease.
2. Using antibiotics only when needed - Antibiotics should only be prescribed for bacterial infections, not for viral infections. 
3. Avoiding the use of wide-spectrum antibiotics - The use of narrow-spectrum antibiotics (antibiotics specific for the infection) is less likely to lead to antibiotic resistance.
4. Ensuring that patients complete courses of antibiotic treatment - This ensures all bacteria are killed and so does not give them the chance to develop resistance.
5. Avoiding the use of antibiotics in farming - This reduces the chance of bacteria becoming resistant to antibiotics. 

Sources of medicines

Medicines, including antibiotics, are used to ease symptoms, cure diseases or prevent them. They come from a wide range of natural sources including plants, animals, and microorganisms.

Examples of medicines include:  

• Penicillin - An antibiotic extracted from a type of mould.
• Aspirin - A painkiller based on compounds from willow bark.
• Prialt - A pain-killing drug derived from the venom of a cone snail.

Scientists have not yet discovered or analysed all organisms on Earth, so there may be organisms that can provide treatments to currently incurable diseases such as AIDS. These potential sources of new medicines need to be protected by maintaining biodiversity (the variety of different species on Earth). 

Future medicines

New research is focused on the use of personalised medicines to treat diseases. Personalised medicines are medicines that are tailored to an individual's DNA. This means that a patient's genome is analysed before they are given any treatment and so drugs given are more likely to be effective and less likely to cause side effects. 

Another focus for new research is on synthetic biology which involves the use of genetic engineering to develop artificial proteins, cells, and microorganisms. Bacteria or mammals can be modified to produce therapeutic drugs to treat certain diseases.