To Avoid Spreading Germs, Expert Recommends Hand Washing

Thursday, November 5, 2009

Fears of contracting the H1N1 virus this flu season have people steering clear of strangers with coughs and scolding friends who don’t sneeze into their crooked elbows. With everyone trying to stay germ free, hand sanitizer has become a popular means of protection. But although a quick pump from a Purell dispenser is the most convenient form of hand cleaning, is it the best?

Not necessarily, according to Saint Joseph's University medical microbiology expert Michael McCann, Ph.D., who recommends washing with soap and water whenever possible. McCann says this-tried-and true method is still the best when it comes to killing germs and protecting your self from the flu.

However, if you can’t get to soap and water, he suggests carrying an alcohol-based, rather than an antimicrobial, sanitizer. The latter contains chemicals like triclosan, which McCann warns, can cause more harm than good.

"The wide-spread use of antimicrobials by the general public may be a literal case of over-kill," says McCann. "While antimicrobial-containing hand sanitizers and soaps can be very effective at inactivating influenza viruses, over use can be problematic. Research suggests wide-scale application of these sanitizers promotes the evolution of drug-resistant strains of bacteria. Many contain chemicals -- like triclosan -- that specifically kill bacteria, but do not harm us. The problem is, triclosan can trigger 'selection,' which occurs when conditions become favorable or unfavorable for individual bacterium of the same species, based on genetic variation.

In this case, if millions of bacteria are exposed to triclosan, it kills almost all of them. But if one of those bacteria has a genetic mutation that enables it to survive the lethal chemical, then the application of triclosan will select for that individual. Only bacteria resisting the chemical survive.

Descendents of resistant bacteria also carry the mutation, which leads to the generation of large populations of resistant organisms. "This is exactly what has happened with antibiotics, and why strains of bacteria like MRSA (Methicillin-resistant Staphylococcus aureus) are no longer susceptible to many commonly used antibiotics," he adds.

McCann says studies have shown sanitizers that use alcohol -- ethanol and/or isopropyl-- are more effective at killing microorganisms and inactivating viruses than triclosan. Further, there does not seem to be a mechanism by which bacteria and other organisms can evolve resistance to alcohols -- another reason to use these products.

Media Contact

McCann, a professor of biology and associate dean of the College of Arts and Sciences, can be reached for comment at 610-660-1823 or, or by calling the Office of University Communications at 610-660-1222,

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