Because bacteria grow rapidly, a single cell can potentially produce millions of new cells each day. As they divide and reproduce, these cells have a natural tendency to change or mutate. Since the 1950s, due in part to the improper use of antibiotics, mutations have led to bacteria developing traits that make them more resistant to antibiotics and thus more of a threat to public health. Through a complex process that involves the exchange of genetic information, some bacteria can even pass resistance along to unrelated strains of bacteria. As people travel around the world they can spread resistant bacteria to other areas, further magnifying the extent of the problem.
Antibiotics kill bacteria or arrest bacterial growth in a number of ways.
Some, such as the quinolones and Rifampin, attack bacteria by interfering with their ability to divide. Others, such as the tetracyclines or aminoglycosides, prevent the manufacture of certain proteins essential to the bacteria. Penicillin antibiotics attack the ability of the bacterium to construct its cell wall. Through mutation , however, certain bacteria have acquired the ability to make a protein called penicillinase that destroys penicillin. Fortunately, scientists have been able to synthesize or make new antibiotics that penicillinase cannot destroy.