Antibiotic resistance is defined as the increased tolerance of specific type of bacteria against specific types of antibiotics. This means that the microorganism can withstand the therapeutic dose of the antibiotic without showing any effect on the microorganism.

The scientists searched for a long time before they discovered the real reasons for antibiotic resistance. The first cause was the usage of sub - therapeutic doses of antibiotics over a long period of time. This appeared when the farmers used antibiotics as a growth promoter in their animals' feed. The antibiotic residues that are present in meat will enter the body of the consumer and start to accumulate gradually giving time for the pathogenic microorganisms to adapt with it and develop resistance.

Another important reason for antibiotic resistance is the administration of low doses of antibiotic in some household items or toys which was thought to combat daily infections in children but lately, it was discovered to be one of the main reasons for developing antibiotic resistance against specific species like staphylococcus aures.

Antibiotic resistance occurs through what is called natural selection and mutation. The simple explanation for this process is that when an antibiotic is administered to combat a certain species of microorganisms it may cause a mutation in the genetic code of some microorganisms of this specific species causing them to survive the course of antibiotic so, some of these microorganisms will die and the mutant microorganism will tend to replicate and spread the mutant gene between them horizontally, and the colony became fully resistant to that type of antibiotic.

Scientists discovered an important use of the drug resistance and they started to use it in genetic engineering. The simple idea behind that is binding the gene that they want to add to the microorganism with the resistance gene then they introduce it to the population of the colony, after that when the antibiotic is introduced to the same colony, the microorganisms that failed to implement the new gene and the resistance gene will die from the effect of antibiotic leaving the mutant microorganism only in the colony.

While this is a useful usage of antibiotic resistance but scientists are still looking for a solution for antibiotic resistance in humans. The first solution was the development of new types of antibiotics to help overcome the antibiotic resistance against the old drugs. This is a continuous method because after a while, a specific microorganism will develop resistance against the new drug and scientists will start looking for another new antibiotic.