The Biology of Hand-Washing by pptfiles


									The Biology of Hand-Washing
Your Mother Was Right: In an age when antibiotics don't kill germs very well, soap does
By Gurney Williams III DISCOVER Vol. 20 No. 12 | December 1999

Zung Wan Kim, a surgeon in Port Chester, New York, preps for surgery like a prizefighter before a major bout. First he punches a soap dispenser button with his foot and delivers a low blow to a faucet switch with his knee. Then he rubs the soap over his hands for more than a minute and rinses it off with graceful left and right hooks under the stream of water. He jabs at his nails with a sterile brush for more than another minute, rinses, scrubs his hands with a sterile sponge, rinses again, and then repeats the initial wash and rinse. Ding! The bell goes off on Kim's timer, ending a full five-minute round of hand-washing. Seem obsessive? Sure, until you consider that the life of the hernia patient next door depends on Kim’s routine. And recent events have shown that even ordinary hand-washing may once again become a matter of getting really sick or staying well. In August of this year, federal health experts reported that four children in Minnesota and North Dakota were fatally infected by Staphylococcus aureus, a bacterium easily passed through hand-to-hand contact. A strain of S. aureus has in recent years become resistant to the popular antibiotic methicillin. Yet any good hand-washing can still send it down the drain. Lulled by the success of antibiotics in general, Americans have come to think of compulsory handwashing as a thing of the past. But more than half the staph infections caught by hospital patients are now resistant to methicillin (up from 2 percent in 1974), and according to some epidemiologists, the deaths in Minnesota and North Dakota are just the tip of the iceberg. ―With the possible exception of immunization,‖ says Ralph Cordell, an epidemiologist at the Centers for Disease Control and Prevention in Atlanta, ―hand-washing is the most effective disease-preventing measure anyone can practice.‖ ―There are more than 100 trillion bacteria that inhabit your body. And they aren't just silent partners. They digest your food, make vitamins, and protect you from pathogens. A recent study has found they may even play a role in regulating appetite and weight. ―EYES - Natural antibiotics in tears kill most organisms, but the eyes are home to a few hardy forms— mostly harmless strains of Staphylococcus, such as S. epidermis, and Streptococcus—that keep more virulent strains, such as pinkeye-causing Moraxella or Chlamydia trachomatis, at bay. ―EARS - Although waxy secretions contain antibacterial components, more than 200 bacterial species normally live in the outer ear. ―NOSE - At least 20 percent of us carry a virulent strain of Staphylococcus aureus. Normally it's not much of a problem, unless a cut lets it into the bloodstream. Then it can be serious and even fatal. ―MOUTH - Of the estimated 500 microbial species in the human mouth, only 150 have ever been cultured in laboratories. On your teeth, Actinomyces viscosus secrete plaque, which traps volatile sulfur producers and acid-leaking Streptococcus mutans, the cause of bad breath and cavities. ―ARMPITS - Most of the 12 trillion or so total skin bacteria prefer the moist climate of the armpits and groin, where urea, protein, salts, and lactic acid leak out of sweat ducts and gather around hair follicles. Some people are hosts to more of the Corynebacterium species that feast on these odorless compounds and convert them to 3-methyl-2-hexenoic acid, the volatile compound that makes armpits smell distinctive. ―STOMACH - Once thought too acidic to harbor life, it is now known to harbor the bacterium Helicobacter pylori, which can cause ulcers in some people.

―COLON - There are over two pounds of bacteria in your colon, and they make up a third of human feces by weight. Predominantly composed of the anaerobic members of the phyla Bacteroidetes and Firmicutes, these organisms metabolize bile acids, break down indigestible parts of our food, and produce vitamins K and B12. A study last February identified a strain capable of contributing to obesity by disrupting the appetite-regulating hormone ghrelin. ―URINARY TRACT - The urethra is normally sterile, except for the half inch near the exit. Urinary tract infections occur when certain strains of colon-dwelling Escherichia coli (E. coli) bacteria manage to colonize the opening and migrate upward. ―REPRODUCTIVE TRACT - Various species of Lactobacillus keep the vagina at a slightly acidic pH ranging from 4 to 5. If the bacteria are killed off, the pH goes up, encouraging the overgrowth of Candida fungus. ―FEET - Various species of moisture-loving bacteria flourish between the toes. Some ferment acids, producing the smell of sweaty feet. ―STERILE AREAS – include liver, gall bladder, brain, thymus, blood, lower lungs‖ (Are Antibiodics Killing Us by Jessica Snyder Sachs. Discover, Oct 2005). The above mentioned list of bacteria that colonize your body leaves some readers uneasy and reaching for the closest antibacterial product to rid themselves of these pesky guests. However, the overuse of antibacterial soaps and cleaning products has led to a generation of bacteria that are resistant to antibiotics. Now when people are sick, the antibiotics normally used to wipe out the bacterial infection are no longer working. To avoid breeding antibiotic resistant bacteria, do not use antibacterial soap and "bacteria-fighting" cleaning products. These products kill 'good' bacteria which fight bad germs. Cleaning with soap and water, or disinfecting surfaces with a solution of water and vinegar or household bleach is adequate. While many bacteria live on our bodies that are beneficial, there are many more bacteria that are harmful and the majority of harmful bacteria live on our hands. The solution is simple. Start with soap and running water at a comfortable temperature. (Antimicrobial soaps are unnecessary and they may help spawn bacteria resistant to antibiotics.) As soon as the soap hits your skin, islands of grease will begin to dissolve, exposing dormant viruses and living bacteria. E. coli and other intestinal transients will get caught up in the tide of soapy water during the first five seconds of the wash. Plain soap tears off the outer coating of flu viruses, rendering them inert. Hand-washing also flushes away yeast and other fungi, and the grapelike clusters of staph will soon slide away as well. Keep rubbing your soapy hands—in glee, if you like, at this microbial rout—for at least 15 seconds before rinsing. Admittedly, that is likely to seem like a long time. To be sure you don’t give up too soon, hygienists recommend washing for as long as it takes to sing ―Twinkle, Twinkle, Little Star.‖ If you do all this, you will wipe out as much as 95 percent of the organisms that were there before you picked up the soap. If you’re in a hurry, rub on an alcohol gel fortified with a skin-protecting emollient like glycerin, or wipe your hands with an alcohol-laden towelette. No matter how long you wash, the ancient flora will soon reemerge from hiding—from subungual spaces, sweat glands, hair follicles, and skin folds—and bloom again. For surgeon Kim and the rest of us, there will be many more rounds in this fight. But you know what to do: Shake hands at your own risk, and keep washing until that nursery song drives you nuts.

Name ___________________________

The Biology of Hand Washing Questions
Standard Biology


Which bacterial shape is Staphylococcus aureus? ________________


What can be used to treat a bacterial infection? ________________________________________________________________________ ________________________________________________________________________


How does hand washing with soap prevent bacterial infection? ________________________________________________________________________ ________________________________________________________________________


What does it mean for bacteria to be resistant to antibiotics? ________________________________________________________________________ ________________________________________________________________________ Suggest a way that using antibacterial products can breed ―superbugs‖. ________________________________________________________________________ ________________________________________________________________________



A significant number of individuals experience food poisoning each year. Suggest a way to prevent food poisoning in each of the following situations. a. How can you prevent food from growing bacteria? __________________________________________________________________ __________________________________________________________________ b. How can an individual keep themselves from ingesting bacteria that might be on their hands? __________________________________________________________________ __________________________________________________________________


Pregnant women are not supposed to eat cheeses that are soft since they haven’t been pasteurized. Pasteurized means the cheese wasn’t heated to a temperature that would kill bacteria. Suggest why eating these cheeses could be dangerous for a growing fetus. ________________________________________________________________________ ________________________________________________________________________


Why do restaurants have signs in the restrooms reminding employees to wash their hands before returning to the kitchen? ________________________________________________________________________ ________________________________________________________________________


Why is washing your hands before you eat so important? ________________________________________________________________________ ________________________________________________________________________

10. How has this article changed the way that you view hand washing? ________________________________________________________________________ ________________________________________________________________________

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