How much Influence does selection has on antibiotic resistance?

The Influence of selection on antibiotic resistance is enormous influencing the rate of mutation. After a mutation that is potential to cause antibiotic resistance phenotype has occurred the bacteria with the mutated allele must compete with the wild -type ancestral bacterium. The degree of competitiveness and the result depends on the relative fitness of the mutant cell compared to the wild-type ancestral population. And therefore the ability to mutate and the selective process plays a major role in determining the rate of mutation. Antibiotic resistance changes bacterial fitness by decreasing or increasing. In the event it is decreased in fitness bacteria is normally cleared quicker before selection. However this decreased fitness can be compensated by other mutations in different loci of a chromosome resulting to equal or higher in fitness of the mutant allele compared to the wild-type ancestor. Furthermore, increased fitness in the antibiotic resistant bacteria brings about enormous mutation rates. Other factors that are important in the selective process are antibiotic concentrations and the physical structure of the selective habitat.