Evolution and Antibiotics

Antibiotic resistance is a heritable trait in microorganisms that enables them to survive in the presence of an antibiotic. An antibiotic inhibits the production of bacterial cell walls (Antibiotic Resistance of bacteria, 2007); some inhibit the synthesis of proteins while others inhibit the synthesis of proteins, while others inhibit the replication of bacterial DNA.

Mutations are the primary source of genetic variation. Accidents in DNA are called mutations. In bacteria, a mutation of a specific gene occurs in about every 10,000,000 cell divisions. Because of their fast generation times, large population size, and methods of gene bacteria sometime develop resistance to even powerful antibiotics. Resulting in the number of antibiotics that can be used against certain diseases is dwindling.

An antibiotic kills a bacterial cell by simply disrupting a critical function. The antibiotic binds to a protein so that the protein cannot function properly. Antibiotics are often overused, and misused. Doctors often prescribe antibiotics in incorrect doses or a wrong one for the bacteria they are trying to treat. A bacterium that is continuously exposed to antibiotics creates a strong selection of these bacteria to evolve resistance. The more a bacteria is exposed to antibiotics the greater the selection pressure on the population to evolve resistance. The rate the evolutionary change occurs depends on the strength of natural selection "survival of the fittest".

As the use of antibiotics became more widespread, the prevalence of antibiotic resistant bacteria increases. The widespread development of multi-drug resistance in many species of bacteria led scientists to believe that another mechanism beyond spontaneous mutation was responsible for the acquisition of antibiotic resistance. An existing species adaptation to the antibiotic and modifies so that it no longer affects the microorganism.

The rate of resistance rises by the widespread misuse of antibiotics. Antibiotics in animal feed, and unfinished antibiotic prescriptions are causes for an accelerated rate of resistance development. Giving antibiotics to livestock in animal feed is similar to giving people antibiotics all their life even when they are healthy. Often, prescriptions for antibiotics are taken when antibiotics are prescribed for viral infections (though an antibiotic does not work on viral infections); this gives the opportunity for benign bacteria to acquire resistance that can be later passed on to pathogens.

If a person takes an antibiotic in a high dose for its entire cycle, the more bacteria will be killed. The bacteria greatly decrease the chance that one bacterium will mutate into a resistant form. However, if a person does not take the antibiotic for the full cycle, more bacteria will survive which means there is a greater chance for the bacteria to mutate.