How can an antibiotic resistant strain of bacteria occur?
antibiotic resistance can occur through selection of existing variations and rare mutations from the loss of genetic information.
Bacteria multiply so rapidly that a single cell can grow in to ten million in six to eight hours.
Because of crossing over in mitosis and the exchange of genetic material between bacterial cells there a millions of variations between the bacterial cells.
The two or three cells that carry the combination of genes that grant them resistance for the antibody survive and pass their successful gene to their descendants. This is selection from existing variations.
Investigators found that in strains of bacteria had developed resistance by dropping from its chromosomes a gene called kat G.
The cells had paid a price to defend themselves from the antibiotic .
The cells had made an evolutionary trade-off giving up part of their own adaptive equipment for the sake of survival
(The Beak of the Finch Jonathan Weiner 1994 pages 258-260)
Research indicates that bacteria develop resistance by mutations that result from the loss of genetic information or the selection of existing combinations of genetic information.