Problem 7 - Campbell Biology

Question

EVOLUTION CONNECTION In patients with nonresistant strains of the tuberculosis bacterium, antibiotics can relieve symptoms in a few weeks. However, it takes much longer to halt the infection, and patients may discontinue treatment while bacteria are still present. Explain how this could result in the evolution of drug-resistant pathogens.

Step-by-Step Solution

Answer

Incomplete antibiotic treatment allows slightly resistant bacteria to survive and reproduce, leading to drug-resistant pathogens.

Step 1 - Understand the Role of Antibiotics

Antibiotics are used to kill bacteria responsible for infections. When antibiotics are administered, they target and eliminate most of the disease-causing bacteria in the patient.

Step 2 - Explain Partial Treatment

When a patient discontinues antibiotic treatment early (after symptoms are relieved but before the infection is fully eradicated), not all bacteria are killed. Some bacteria that may survive are those less sensitive or slightly resistant to the antibiotic.

Step 3 - Survival and Reproduction of Resistant Bacteria

The bacteria that survive the partial treatment are more likely to carry resistance traits. These bacteria reproduce, passing on their resistant traits to their offspring.

Step 4 - Evolution of Resistant Pathogens

Over time, the population of bacteria within the patient shifts towards an increasingly resistant group. As these drug-resistant bacteria continue to proliferate, they can result in an infection that is much harder to treat with standard antibiotics.

Step 5 - Implications for Treatment Practices

This situation underscores the importance of completing prescribed antibiotic treatments to ensure that even slightly resistant bacteria are fully eradicated, preventing the evolution and spread of drug-resistant strains.

Key Concepts

partial antibiotic treatment

When patients feel better, they might stop taking antibiotics prematurely. They think the infection is gone because the symptoms are relieved. However, not all bacteria may be killed by this point. Those that survive can have a mild resistance to the antibiotic. This happens because the full course of antibiotics is designed to kill even the slightly resistant bacteria. Stopping the treatment early means those slightly resistant bacteria get a chance to live.

survival of resistant bacteria

After partial antibiotic treatment, the bacteria that survive are often the slightly resistant ones. These bacteria were not fully destroyed by the antibiotic. They may have started with slight resistance, or developed it during the treatment. Because they can survive where other bacteria can't, they continue to live and multiply. This selective survival is crucial as it allows resistance to become more common in the bacterial population.

reproduction of resistant traits

The surviving bacteria can reproduce, and they pass their resistant traits to their offspring. Unlike most living things, bacteria can reproduce very quickly. When resistant bacteria reproduce, they create more bacteria that also carry resistance. This means that the resistant traits spread quickly. Over a short period, a once small group of resistant bacteria can become a large population. This makes the infection harder to treat with the same antibiotic.

evolution of drug-resistant pathogens

As time goes on, the bacteria within the patient become more resistant. Even if antibiotics are used again, they might not work as well. The overall population shifts towards a more resistant group, making the original infection more difficult to cure. In some cases, infections can become entirely resistant to a specific antibiotic. This continual adaptation of bacteria to survive antibiotics is a prime example of evolution. This is how the problem of drug-resistant pathogens becomes more serious over time.

importance of completing antibiotic treatments

To prevent the evolution of drug-resistant bacteria, it is crucial to complete the entire antibiotic treatment as prescribed by a doctor. This ensures that not just the sensitive bacteria are killed, but also the slightly resistant ones.

• Finishing the full treatment course kills all bacteria.
• This prevents the survival and reproduction of resistant bacteria.

Completing the treatment helps keep infections from becoming drug-resistant. This underscores the importance of public health education on the proper use of antibiotics. Everyone must understand why finishing the full course is key to preventing drug-resistant infections.