Natural selection: antibiotic resistance

There is variation within bacterial phenotypes. Some are resistant to antibiotics and some are not.

Treating bacteria with antibiotics provides competition.

The resistant individuals survive and the non-resistant individuals do not survive – this is differential survival.

The resistant bacteria are able to reproduce.

The resistant bacteria pass on the resistance gene to the next generation.

Resistant bacteria increase and non-resistant bacteria decrease in number.

The gene for antibiotic resistance is usually caused by a beneficial mutation in the bacterial cells.