After taking antibiotics for several weeks, a patient develops a severe bacterial infection in his intestines. The doctor claims the antibiotics changed the microbiome of the patient's gut, causing the infection to develop. What evidence would the doctor need to support the claim? Explain how competition and succession played a role in developing the bacterial infection.

Before the antibiotic, the 'good' bacteria had colonized her intestines and formed colonies that made up her biome. These colonies out-compete other bacteria, including 'bad' bacteria that tried to grow in the intestines hence protecting her intestines from infection.

However, the antibiotics wiped out the established colonies of 'good' bacteria - destroying her biome - and gave room for recolonization of the intestines by bacteria. The secondary succession gave a chance for the 'bad' bacteria to also thrive and cause her massive infections.