The process by which organisms with traits that help them survive and reproduce tend to pass on those traits more often than organisms without those traits. In this case, bacteria with antibiotic resistance mutations are more likely to survive and reproduce.
A small ring of DNA found in bacteria that can carry antibiotic resistance genes and be transferred between bacteria.
Superbug: A strain of bacteria that has become resistant to multiple types of antibiotics, often due to the accumulation of several antibiotic resistance mutations.