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Infection Control

Tough Questions About Disinfectants Answered

September 19, 2010
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In an era of H1N1 (swine flu), MRSA and other contagious illnesses that can be transmitted environmentally, and directly or indirectly by surfaces, disinfectants clearly have a place in our clean-for-health toolbox.

Still, the use of disinfectants presents several pressing questions, such as: Since these products are pesticides, are they just too toxic to use routinely? Do disinfectants cause antibiotic resistance? What about the recent report from the Society for General Microbiology stating that disinfectants can make bacteria resistant to treatment?

The following questions and answers look to address these issues.

Q: Since disinfectant products are pesticides, are they just too toxic to use routinely?

A: No doubt about it, we are often "trigger happy" when it comes to trying to destroy germs or microbes, since most are essential to and part of life.

We do not want to poison or attempt to routinely destroy all germs.

As Philip M. Tierno Jr, Ph.D, director, Clinical Microbiology & Immunology, New York University Medical Center, and associate professor, Departments of Microbiology & Pathology, New York University School of Medicine, referenced in his book, The Secret Life of Germs:

"First, we must understand the important role germs play as recyclers of complex organic matter on planet Earth, and in the maintenance of our own health. Germs in the normal human flora can prevent establishment of pathogenic germs in our bodies and also provide us with nutritive materials. Therefore, we must never entertain the notion that all germs are bad and should be eliminated. That is neither possible nor desirable. Because germs are ubiquitous (including in and on human beings), we must learn to live with them. Hence our protective strategy should be focused on reducing the risks of infection."

Moreover, overuse of disinfectants in our facilities definitely poses risks to human and environmental health, just as overuse of bug spray does in our homes — plus it wastes money.

Thus, "routine use" should be restricted to "where needed" to control dangerous pathogens.

However, we should not underestimate the importance of "where needed."

Think of discovering a black widow spider infestation in your home — a species resistant to many pest control methods.

Would you want to experiment with non-toxic and less effective means of control and risk someone being bitten and injected with highly toxic spider venom?

Sometimes the benefits of a "quick kill" far outweigh the risks of proper use of an EPA-registered pesticide — or disinfectant.

Q: Do disinfectants cause antibiotic resistance?

A: It''s misleading to imply or state outright that antibacterial products (i.e., Triclosan) and disinfectants (quats, phenolics, etc.) can — like antibiotics — routinely produce resistant bacteria or "super germs" that endanger public health.

While bacterial-resistance has been proven to develop with antibiotics (they work inside or on the body, and therefore cannot be as immediately lethal as antibacterial and disinfectant products used outside the body) — generally speaking, antibacterial products and disinfectants, unlike antibiotics, directly kill germs, without the strong possibility of resistance developing.

At the risk of oversimplifying, while antibiotics impair the functioning of germs leaving some to survive and develop resistance, the consensus among scientists is that disinfectants work somewhat like "sledgehammers" and there is simply nothing left alive to develop resistance.

Triclosan (used in antibacterial hand soaps and to impregnate certain products) is more controversial and the debate goes on as to its actual ability to create dangerous antibiotic resistant bacteria with significant impacts in the real world.

With properly-used disinfectants in the context of JanSan operations, bacterial resistance apparently never happens — at least as far as we know.

According to Dr. Chuck Gerba, professor of Environmental Microbiology in the Departments of Microbiology and Immunology and Soil, Water and Environmental Science at the University of Arizona, "No resistance to chlorine has ever occurred despite its use for over 100 years. The same can be said for quats. While you do see some tolerance to quats develop by some microorganisms, it still has not prevented the widespread use of quats since they are still effective at the dosages used. Actually, in our studies of disinfectant use in daycare centers we saw a reduction in the number of antibiotic-resistant bacteria in the daycare and a reduction in the antibiotic use among the children. I think the bottom line is that cleaning and disinfectant use saves lives, and actually reduces the use of antibiotics."

According to Benjamin D. Tanner, Ph.D., president, Antimicrobial Test Laboratories, "Cross-resistance to antibiotics from disinfectants is not easily demonstrable outside of lab settings, but is a possibility nonetheless. Still, the risks of not disinfecting contaminated surfaces far exceed any possible cross-resistance risks … cleaning without disinfectants may not solve today''s infection control problems (MRSA, VRE, C. diff) like it helped to solve yesterday''s. In fact, it could actually make them worse if pathogens were to be spread around a facility during the cleaning process."

Q: What about the recent report from the Society for General Microbiology stating that disinfectants can make bacteria resistant to treatment?

A: The report states, "Chemicals used in the environment to kill bacteria could be making them stronger, according to a paper published in the October issue of the journal Microbiology [reporting on a study by Dr. Kaatz]. Low levels of these chemicals, called biocides, can make the potentially lethal bacterium Staphylococcus aureus remove toxic chemicals from the [bacterial] cell even more efficiently, potentially making it resistant to being killed by some antibiotics."

The key point, stated later, is this: "At the correct strength, biocides kill bacteria and other microbes. However, if lower levels are used the bacteria can survive and become resistant to treatment."

The moral?

Use the right disinfectant and dilution, and apply it correctly.

According to Dr. Jay Glasel, professor emeritus in the Department of Microbial, Molecular and Structural Biology at the University of Connecticut Medical/Dental School in Farmington, Connecticut, "Resistance does not develop in bacteria exposed to sufficient doses of biocide … The cautionary tale that the Kaatz paper relates is that biocides used in disinfection to remove Gram-positive microbials should be of sufficient concentration to kill them quickly."

On balance, and in light of current evidence, antibacterial and disinfectant products have their proper place in our quest to reduce the risk of infection and protect health.

Cleaning is still the best first line of defense, but due to the effectiveness of disinfectants used properly and where needed, it is not the only one.


Allen P. Rathey is president of Boise ID-based InstructionLink/JanTrain.

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