Antibiotic resistance (or resistance) can develop due to the natural selection of random mutations and excessive exposure to antibiotics. Microorganisms can transmit genetic information on antibiotic resistance through horizontal gene transfer. Resistance occurs in one of three ways: natural resistance in some types of bacterias, genetic mutations, or by acquiring resistance by one species of bacteria from other microbes. Resistance can also develop due to the gradual accumulation of certain mutations over time, as well as excessive use of antibiotics. Main mechanisms of resistance include:
1. the microorganism lacks the structure that is sensitive to antibiotics;
2. the microorganism is impermeable to the antibiotic;
3. the microorganism converts the antibiotic into an inactive form;
4. altered metabolism of the microorganism bypasses the reactions suppressed by the antibiotic.