Why have some antibiotics stopped working as effectively?

Answer 1

Antibiotics are substances which, in high dilution, either prevent bacteria form growing or destroy bacteria. They are becoming less effective because widespread use of antibiotics is selecting those bacteria which have abilities to survive the affects of the antibiotics. In effect we are seeing evolution in action.

Answer 2

Because antibodies are used to kill bacteria they are usually ment for only one of the bacterias in our bodies. The antibiotics stopped working effectively because the bacterias have become immune to them.

Answer 3

Some antibiotics aren't effective because the bacteria has evolved to be resistant to the antibiotic. If you have an infection, you must take all the antibiotics prescribed, or else it will only kill the weak bacteria, and the stronger bacteria will multiply and create a strain of the bacteria which is much stronger and antibiotic resistant. This happens with tuberculosis often.

Answer 4

Antibiotics, once a miracle drug, have led to mutations in bacteria. Overuse in sickness as well as in raising cattle and other animals for meat has led to reduced effectiveness.