Lesson 2: Antibiotics and Balance

Key Idea

When a person suffers from a bacterial infection, doctors often prescribe antibiotics. These are powerful medicines designed to kill bacteria to stop the illness.

However, antibiotics are generally not selective. They kill both the harmful bacteria causing the sickness and the helpful bacteria that keep the gut healthy. Consequently, the medicine significantly reduces the total number of bacteria in the microbiome.

Key Idea

A healthy microbiome is characterized by a high diversity of bacteria. This means many different types of helpful bacteria live together, creating a crowded and stable community.

In this crowded environment, helpful bacteria occupy most of the available space and consume the majority of the food. This leaves very few resources for harmful bacteria. This natural competition limits the growth of harmful microbes, keeping the person healthy.

Key Idea

When antibiotics wipe out large numbers of helpful bacteria, the microbiome becomes imbalanced. The reduction in population clears out the previously crowded "neighborhood" of the gut.

This change leaves behind a surplus of available resources, such as food and physical living space. What was once a highly competitive environment now has open territory that is not being used by helpful bacteria.