Sally is working on a farm and cuts her hand whilst opening a gate. The cut becomes infected with bacteria that then invade the tissues of the finger.
The bacteria begin to multiply, each division doubling their number.
There are now too many bacteria for Sally’s immune system to cope with. The infection spreads.

Sally goes to the doctor to get some antibiotics. The doctor prescribes penicillin tablets and Sally begins to take the medicine. Many of the bacteria are killed by penicillin. Some bacteria however are naturally resistant to the antibiotic and so are not killed. These bacteria are said to be adapted to their environment.
The resistant individuals then multiply, increasing their numbers a million-fold in a day. Soon the antibiotic resistant bacteria become very common in the population. Sally’s infection is now very serious and will soon spread throughout her entire body. She returns to the doctor.

1. Does the antibiotic cause the resistance to the antibiotic?
2. In this example, how do you know that antibiotic resistance has a genetic basis?
3. What should the doctor now do to help Sally get better?