Because of the rise in antibiotic resistance, the death rates for some conquered communicable diseases, like tuberculosis, have started to rise again. Antibiotic-resistant pathogens are not more virulent than susceptible ones, but they are harder to destroy. Some produce enzymes that degrade or chemically alter antibiotics, thereby rendering them inactive. Others alter or replace molecules that are normally bound by an antibiotic, changes that essentially eliminate an antibiotic s target in bacterial cells. Bacteria might also eliminate points of entry or develop pumps that push antibiotics out before they have a chance to find their target cells.
Bacteria can acquire resistance genes in several ways.
Many inherit the genes from forerunners. Others will mutuate spontaneously to produce a new, resistant trait or strengthen an existing one. Still others will acquire resistance genes from other bacteria cells in the vicinity. Indeed, the exchange of genes is so inherent that the entire bacterial world can be thought of as one multicellular organism where the interchange of genes is a way of life. The selection process is straightforward.