Antibiotics - Drug Resistance, Antivirals and Antiseptics (GCSE Biology)

Drug Resistance, Antivirals and Antiseptics

Antibiotic Resistance

Currently, the world is undergoing a crisis with regards to antibiotic resistance. Increasingly, strains of bacteria such as MRSA that are resistant to antibiotics are being found.

Bacteria gain resistance due to natural selection:

1. A mutation causes resistance. A mutation gives some bacteria resistance against bacteria.
2. A selection pressure is applied. When antibiotics are given, a selection pressure is applied. The alleles giving antibiotic resistance are selected for.
3. The resistance alleles are selected for. The resistant bacteria are more likely to survive and pass on their resistance alleles to the next generation.
4. Bacteria evolve to become resistant. Over many generations, the bacteria evolve to become resistant.

Antibiotic resistance occurs due to two key factors:

• Overuse of antibiotics – antibiotic resistance has occurred due to overuse of antibiotics, both medically and in farming. Antibiotics add the selection pressure, which speeds up the process on natural selection. Of course, this doesn’t mean we should stop using antibiotics, but they should not be used unnecessarily.
• Incompletion of antibiotic course – when a patient is prescribed antibiotics, they can sometimes stop their course once the symptoms have been alleviated, before the due date of completion. This means that not all the bacteria are killed, and the ones left over tend to be the resistant ones. Therefore it’s important to kill off all bacteria and use antibiotics for the full cycle.

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Viral Drugs

• Antibiotics do not kill viruses. Antibiotics can only kill bacteria, not viruses. This is because antibiotics target processes inside the bacterium and antibiotics can’t attack human host cells in which viruses replicate. We talk about bacteria and viruses together a lot, because they both cause many diseases, but they are very different in structure so need different drugs.
• Viral drugs are used for viral diseases. Antiviral drugs are required to kill viruses. However, these drugs are not as common, as they often damage host cells whilst killing viruses. Moreover, many of them do not actually kill viruses, but just slow down the development of the viruses.

Antiseptics

• Antiseptics stop or slow down the growth of microorganisms. This helps prevent the spread of microorganisms and reduce the risk of infection.
• Antiseptics are used in sterilisation. As they help prevent the growth of microorganisms, they are used to sterilise equipment in hospitals or in other medical settings.