Suggest how natural selection has increased the number of resistant bacteria strains in hospitals

Bacteria are cells which have natural genetic mutations, thus some bacteria will have advantageous mutations in their DNA. The use of antibiotics in hospitals create a selection pressure on the bacteria population. This means that most bacteria will be destroyed by antibiotics, but some bacteria with advantageous genetic mutations will survive. If a course of antibiotics is not completed, the surviving bacteria will be able to replicate (as competition from other bacteria has already been removed) and the prevalence of resistant bacteria increases.