Antibacterial Soap:
Common Cold Killer or Dangerous Fad?
When you catch a cold, do you blame your kitchen countertops? Or does your mind return to the image of that guy you saw sneeze after he made your mocha at Starbucks? The next time you are in your kitchen, look at the area where you prepare food. Do you wonder how many disease-causing bacteria could be living there? There most certainly are some. But don’t let that image drive you to throw down this magazine and run for the antibacterial cleanser under the sink. Right now it is pretty tough for those bacteria to make it into your body and begin wreaking havoc, because there just aren’t enough of them right there in your kitchen. But TV commercials for antibacterial cleansers would have you believe otherwise. Those cheery soccer moms want you to be so afraid of the bacteria living in your kitchen that you make sure to buy their product—the one that “kills 99.9% of bacteria.” Now, it’s true that bacteria can cause illness, and as humans we are often at odds with bacteria, but we just can’t kill them all. If we try, we could see our plans backfire and send ourselves into a new and precarious future of disease. To understand how, we simply need to take a look at how bacteria have become rapidly resistant to antibiotics, and we see a story unfolding that begins with penicillin as an attack on disease and now has become a Frankenstein’s monster of sorts.
Since the 1950s, antibiotics have been widely available and frequently prescribed, and consequently our overuse of and dependence on antibiotics has left us powerless against new, stronger bacterial species capable of causing life-threatening illnesses, such as tuberculosis. In their valiant effort to create safe, disease free environments, hospitals have unwittingly contributed to the proliferation of antibiotic resistant bacteria. Although these “superbacteria” are now found mainly in hospitals, a new wave of household products containing antibacterial agents could spread the danger to our homes. The agents are mixed into soaps, detergents, and lotions, and can even be impregnated into such items as toys, carpet, pillows, socks, sponges, and cutting boards. As consumers, we may feel a sense of security by purchasing and using antibacterial products, but if we go overboard and attempt to establish a sterile, germ free environment in our homes, we will find ourselves breeding bacteria that are highly resistant to antibacterials, and, possibly, to antibiotics as well.
Bacteria are microscopic, single celled entities that can be found on inanimate surfaces and on parts of the body that come in contact with the outside world, such as the skin, mucous membranes, and the lining of the intestinal tract. Some kinds of bacteria cause disease, but most bacteria are benign. In fact, the natural bacterial flora of the body is instrumental in protecting us from disease by competing with disease causing, or pathogenic bacteria. The competition limits the pathogens and often prevents them from multiplying aggressively and causing illness. However, antibiotics do not know the difference between “good” and “bad” bacteria. They kill indifferently, and only the bacteria with any resistance to the antibiotics have a chance of survival. Good or bad, the resistant bacteria are the ones to be worried about.
Bacteria that are resistant to antibiotics owe their drug insensitivity to resistance genes. The genes may code for “pumps” that eject the drugs from cells, or they might activate enzymes that break down or chemically alter the antibiotics. Resistance genes can reside on the bacterial chromosome or, more typically, on another source of genetic information in the cell called a plasmid, which is a small ring of DNA that readily travels to surrounding bacterial cells and exchanges genes with other plasmids. In fact, plasmids so frequently exchange genes with other bacteria that they can be compared to characters on a soap opera: if they hang around long enough, they will eventually exchange genes with everyone.
As if plasmids were not busy enough, bacteria can acquire resistance genes through a few other routes as well. Many simply inherit the genes from their parent bacteria. Others acquire resistance genes by taking up free-floating DNA from the surrounding environment. Other times, genetic mutations, which occur frequently and easily in bacteria, will spontaneously introduce a new resistance trait or will reinforce one already present. A healthy person’s other archenemy, the virus, can also aid in the transfer of genes from one bacterium to another by extracting a gene from one bacterial cell and injecting it into a different one. Imagine a cocktail party, where people are meeting and exchanging phone numbers. If the bacteria are the partygoers, and the phone numbers are the genes, viruses are like the married busybody matchmaker introducing two strangers. Therefore, just as there are a lot of ways to meet people and network at a party, bacteria have as many ways to spread advantageous genes throughout their microscopic community.
Regardless of how bacteria acquire resistance genes, commercial antibiotics can promote the survival and propagation of antibiotic resistant strains, contributing to their own undoing in the selection. Antibiotics promote resistance in a fairly straightforward process. When an antibiotic attacks a population of bacteria, cells that are susceptible to the drug will die off quickly. Those cells with a small amount of resistance will die only after a greater quantity of the medicine is administered, and cells with a high resistance will survive to proliferate. When faced with an antibiotic, the most resistant cells will inevitably out-compete all others. By indiscriminately wiping out all but the resistant bacteria, antibiotics set the stage for the development of a new “superbacteria.” With both “good” and “bad” bacteria remaining, and because plasmids are eager to mingle with each other, a stronger resistance can progress. Moreover, the pathogens can give their disease causing genes to the benign cells, yielding the fearsome super pathogen.
When you use prescription antibiotics, you are unleashing this process in your body. But the growing household use of antibacterial products unnecessarily sets the ball in motion for those bacteria residing outside of our bodies—on countertops, toys, socks, or carpet. Touting the effectiveness of antibacterials, advertisements brazenly prey upon our desire to protect our household and our children. Commercials show concerned spokesmoms wiping down the kitchen counter where tonight’s chicken was defrosting, and the antibacterial cleanser on her sponge will kill 99.9% of germs, like the dreaded salmonella or E. coli. Regrettably, that leftover, seemingly insignificant 0.01% could become the real nightmare.
Like antibiotics, antibacterials can alter the mix of bacteria by knocking out susceptible bacteria and promoting the growth of resistant strains. These resistant bacteria, that may have been present in the household environment all along, but were previously unable to gain a foothold, are now able to thrive and proliferate because of the destruction of their competitors. Sometimes, the resistance to a particular antibacterial is carried on a plasmid that also codes for the resistance to an antibiotic. Hence, by promoting the growth of bacteria carrying such plasmids, antibacterials may actually foster the rise of double resistance—to antibiotics as well as antibacterials.
Triclosan, an antibacterial agent commonly used in soaps, lotions, and other consumer products, has been studied recently to determine whether or not antibacterials pose a threat to consumers. In August of 1998, the Soap and Detergent Association, an organization that represents manufacturers such as The Dial Corporation, Dow Corning, The Clorox Company, and Colgate-Palmolive, released the results of a study conducted by the Food and Drug Administration (FDA), which concluded that triclosan-based products had controlled or reversed outbreaks of bacterial infestations in hospitals.1 Yet, in the same week, germ hunters from Tufts University Medical School in Boston published a study in the journal Nature that conflicts with the earlier FDA results. “People think they are sterilizing the world by using these products and, in fact, they are potentially changing it,” said Dr. Stuart Levy, director of the Tufts research group. “They are really over-the-counter antibiotics.”2 The group found that triclosan is not the general acting agent it was previously thought to be. In tests on an E. coli bacterium, Levy’s group determined that triclosan actually has a specific target—an enzyme involved in making the cell wall of the bacterium. 3 This is the same method that an antibiotic uses to fight tuberculosis. As TB has become more and more resistant to antibiotics in the past decades, so too will the bacteria in our homes, if triclosan-based products are overused.
The first line of defense against infection is simply washing your hands with normal soap and water. When handling food, wash fruits and vegetables thoroughly and avoid raw eggs and undercooked meat, especially in ground form. Bacteria thrive at temperatures ranging from 40°F to 140°F. Decreasing the amount of time your raw food spends between the refrigerator and the oven will also decrease the exposure to bacteria. Hence, simply defrosting a chicken in the fridge thaws the chicken, and protects from salmonella. Routine housecleaning is surely necessary, but standard soaps and detergents with no added antibacterial agents decrease the numbers of potentially troublesome bacteria perfectly well. Similarly, quickly evaporating chemicals, such as bleach, alcohol, ammonia, and hydrogen peroxide can be used with an added benefit. They safely remove potential pathogens from, for instance, thermometers or utensils used to prepare raw meat for cooking, but they do not leave long-lasting antibacterial residues that will continue to kill benign bacteria and promote the growth of resistant strains long after the target pathogens have been removed.
If we do not take a step back and examine our excessive use of antibiotics and now, antibacterials, we will make our homes, like our hospitals, havens of ineradicable disease producing bacteria. Consider the town where you grew up. Now imagine the neighborhood, and your house. Remember the kitchen? Picture your mom, doing dishes and wiping down countertops. Now zoom in on your mom’s hand, the sponge, and the countertop. At microscopic levels, these surfaces are not smooth, but pocked and jagged. Every nook and cranny holds hundreds of bacteria. Some are good, and some are bad. When you were growing up, this was the case. Now imagine your children, grown, in their own kitchens. The picture is exactly the same, with millions of bacteria living in your kids’ kitchens. Only your kids notice that they get sick a lot more than they used to or they haven’t been able to treat their illnesses because the bacteria in their kitchen have been bred for superiority and supremacy. They are all resistant, ready to strike.... Now think of your own kitchen. You have the power to keep it as close to the memory of your childhood as you wish. By restricting our use of antibacterial products, we can keep our houses—and our children’s houses—safe. But by attempting to wipe out all bacteria and live germfree, we will catapult ourselves into a dark and uncertain future, where our best cure has become our worst poison.
Levitt Prize, 2000
Instructor: Katie Palmer
Notes
1. “News Release Archive for 1999,” the Soap and Detergent Association web site, 22 May 2001
<http://www.sdahq.org/about/archive99.html#triclosan>.
2. Joseph B. Verrengia, “Some Soaps May Aid Drug Resistance,” AP Online. 6 August 1998, 16 June 2001 <http://web.lexis-nexis.com >; see also Barbara Ingham, “September 1998 Newsletter,” Food Facts for You! 20 June 2001
<http://www.uwex.edu/ces/flp/specialists/ingham/sep98.html>.
3. Verrengia.