Antibiotic resistance is a scary prospect. Before describing what is being done, wrong and right, some background information about bacteria and antibiotics might be helpful.
Bacteria are microscopic organisms roughly ten times smaller than human cells. There are many types of bacteria, and most are beneficial to human life. For example, bacteria break down waste in soil, form a crucial part of the food chain in oceans, and aid digestion in our intestines. A few kinds of bacteria are harmful; these can multiply rapidly inside our bodies and release molecules that can kill our cells. Normally our immune system recognizes these foreign invaders and activates specialized cells and proteins to eliminate them. Occasionally the bacteria out race the immunity patrols. Then the infected person becomes ill and can die if the bacteria take over. Examples of the harmful kinds of bacteria are: Streptococcus, Staphylococcus, Salmonella, Spirochetes, and Mycoplasma pneumoniae.
Bacterial infections leading to illness and death of children and adults occurred commonly, sometimes disastrously, until the 20th century. Then in 1928 Alexander Fleming who studied bacteria in his London laboratory found that Penicillium mold had accidentally grown in one of his experimental plates, and he observed that the bacterial growth ceased in the areas near the mold. From this important observation of the action of a microorganism secretion came the development of modern antibiotics. Fleming, together with chemists Howard Florey and Ernst Chain were awarded the Nobel Prize in 1945 for their work on the discovery, purification, and characterization of the active molecule, penicillin. This first scientifically processed antibiotic is credited for saving the lives of hundreds of thousands of soldiers and civilians during World War II.
Antibiotics are truly “wonder drugs” that we have come to depend on to prevent serious illness and save lives. Since the 1940’s over 2000 antibiotics have been discovered and developed from microorganisms such as soil bacteria. Chemists have played an important role by modifying the basic structures of the antibiotic molecules to make them even more effective and less toxic to human cells. Many antibiotics, like the penicillin family, act by preventing proper construction of bacterial cell wall. Others act by breaking down the bacterial membrane or by preventing processing of the genetic material (DNA and RNA) to make proteins necessary for bacterial growth.
Unfortunately, as antibiotic use has increased dramatically in medicines, antibacterial soaps, and animal feeds, so has the ability of infectious bacteria to resist their damaging effects. How do these “super bugs” arise? Because bacteria multiply very rapidly, individuals containing mutations that can resist the drugs quickly grow up when the sensitive bacteria die out. This is why feeding livestock sub-therapeutic levels of antibiotics and why people taking less than their full prescription of medicine can have very harmful long-term results. Also, “resistance genes” containing these mutations can be passed between different bacteria through a process known as conjugation or by take-up of genetic material from dead bacteria. Examples of bacterial mutations that provide resistance are new enzymes that break down the chemical structure of the antibiotics and membrane proteins that pump the antibiotics out of the bacterial cell before they can reach their targets. Although the antibiotic resistance has been observed for a number of years, a piercing alarm started in the mid 1990’s when common cases of Staphylococcus aureus infections were increasingly found to be resistant to the toughest antibiotic, vancomycin.
It is truly frightening that bacterial infections might once again become untreatable. However, chemists and other biomedical scientists are making significant advances to stay ahead of bacterial mutations by designing new varieties of antibiotic molecules. New information about the detailed structures of the normal bacterial enzymes and those that are mutated are particularly valuable in this effort. Different antibiotics are also being combined for enhanced effectiveness. On another front, the Federal Drug Administration and other government organizations are paying heed to growing evidence of harmful results of dosing livestock with antibiotics and are taking steps to restrict this practice. Although the problem of antibiotic resistance is far from solved, there is hope that awareness and the efforts of scientists, physicians, policy makers, and the general public can keep this menace under control.
Barbara Ann Baird
Ph.D. Cornell University; postdoctoral fellowship at the National Institutes of Health
Cell surface receptors operating in immune responses
Research together with husband, David Holowka, a senior scientist at Cornell; three sons in Ithaca City schools
West Middle School Science Club
West Middle School