How Does the Resistance Spread?
Genetically, antibiotic resistance spreads through bacteria populations both vertically, when new generations inherit antibiotic resistance genes, and horizontally, when bacteria share or exchange sections of genetic material with other bacteria. Horizontal gene transfer can even occur between different bacterial species. Environmentally, antibiotic resistance spreads as bacteria themselves move from place to place; bacteria can travel via aeroplane, water, and wind. People can pass the resistant bacteria to others; for example, by coughing or contact with unwashed hands.
Several studies have demonstrated that patterns of antibiotic usage greatly affect the number of resistant organisms that develop. Overuse of broadspectrum antibiotics – medications that kill almost every bacteria, both good and bad – greatly hastens the development of antibiotic resistance. Researchers have only recently begun to understand the effects these drugs have on the good bacteria in our bodies, which rely on these microbes to perform basic functions like breaking down food and regulating our immune systems.