A chemical that kills or reduces the reproduction rates of organisms. Such chemicals may be secreted by living organisms (such as penicillin, which is produced by certain molds) or they may be artificially synthesized.
Antibiotics sometimes manage to only kill the more susceptible bacteria. The surviving bacteria survive because they can resist antibiotics. The surviving bacteria then reproduce, producing a new generation of bacteria, all of which are resistant to today's antibiotics. This is not good, because it makes infectious diseases harder to fight.
This has produced various strains of bacteria that lead to infections that cannot be treated with the more common antibiotics. An example is the MRSA strain of Staphylococcus aureus, that is resistant to all penicillin-type antibiotics.
- Wile, Dr. Jay L. Exploring Creation With Biology. Apologia Educational Ministries, Inc. 1998