Continuous Disinfectant Spray Limits Airborne Pathogens

Daniel M. Keller, PhD

July 10, 2012

July 10, 2012 (Bangkok, Thailand) — A continuous aerosol spray with a nontoxic alcohol-free disinfectant can control airborne pathogens in patient areas of hospitals and in laboratories.

S.J. Abraham, MD, from the Second Department of Surgery, Faculty of Medicine, Yamanashi University, in Japan, and the Nichi-In Centre for Regenerative Medicine in Chennai, India, presented the microbiologic results of a study here at the 15th International Congress on Infectious Diseases. Researchers tested a spray containing citric acid anhydride, citric acid natrium, and cetylpyridinium chloride (sold as Clinister in Japan). These chemicals are either food additives or have been used for several years in the food industry in Japan.

The chemicals are "delivered in a 5 μm spray using a special humidifier and nebulizer kind of equipment" to remove environmental pathogens from the air, Dr. Abraham told Medscape Medical News. They come as a powder that is mixed with potable (preferably sterile) water. "In an environment of approximately 300 square feet, it brings down most of the disease-causing pathogenic organisms," he said. These include bacteria, viruses, and fungi.

The 5 μm droplets produced in the ultrasonic humidifier can entangle smaller particles and remove them from the air. Airborne bacteria are in the order of 0.8 μm, and viruses are about 0.1 μm.

To test the effectiveness of the spray against common airborne organisms, the researchers inoculated soybean–casein digest agar plates with Escherichia coli or Staphylococcus aureus bacteria, or with Candida albicans or Aspergillus flavus fungi. Control plates and plates exposed to the spray mist were incubated at 37 °C.

After 18 hours of incubation, the control plates containing the bacteria showed confluent growth, but the ones exposed to the spray mist showed no growth or much reduced growth. The mist also inhibited the growth of the fungi to some degree.

The researchers concluded that continuous spraying of the mist should be considered for the disinfection of high-risk healthcare settings, such as intensive care units, old age homes, operating rooms, burn units, and bone marrow transplant units — wherever immunocompromised patients are.

It can also be used in places like airports during pandemics, Dr. Abraham explained. "Even H5N3 [the influenza virus] can be dealt with this way."

He noted that options for air disinfection are limited. Hydrogen peroxide or fumigants of potassium permanganate–formalin are widely used, but these can irritate the eyes and nose, and some might be carcinogenic.

Dr. Abraham explained that the method under study uses compounds that are food additives, that are nontoxic and nonallergenic when contacted or ingested. The continuous use of the spray appears to be safe, and it has a residual antimicrobial effect on surfaces.

As always, the possibility of microbial resistance remains. "They are living organisms...so we need to keep chasing them," Dr. Abraham said.

Hans Liu, MD, professor of medicine at Jefferson Medical College of Thomas Jefferson University in Philadelphia, and an infectious disease specialist at Bryn Mawr Hospital in Pennsylvania, who was not involved in the study, told Medscape Medical News that he sees potential value in this spray.

"We have a lot of people with resistant organisms. The [extended-spectrum beta-lactamase]-producing Gram-negative rods come to mind, as do methicillin-resistant Staphylococcus aureus and C difficile, of course," he said. "We try very hard to disinfect rooms; the problem is that a lot of time, the best cleaning is done after the patient is discharged."

More irritating disinfecting compounds cannot be used in the presence of people because of the risk for toxic or allergic reactions.

Dr. Liu said that he does not have any direct experience with this system, "but it probably has antimicrobial activity; you're basically trying to kill the bugs as they're being shed or spread into the environment. It's a very interesting thought."

However, he wonders whether the chemical components are entirely without risk for toxic effects or irritation, what the cost will be, and whether the mist might select for resistant organisms by eliminating more sensitive ones from the immediate environment. He said that Pseudomonas in general is more resistant to germicidal agents than Escherichia coli, "so I think you have to do the study.... Of course, the eventual proof will be if you use it in a controlled trial with patients, one group versus another, and if the group that uses this spray does a lot better in terms of the frequency of infections, the type of infecting organisms, and length of stay in the hospital — then you may be onto something."

When informed that the powder for the mist costs about $8 a day, he pointed out that such an amount "in the United States is negligible or acceptable. In a lot of Third World countries, that's a lot of money. And of course, [there is the cost of] the device."

Dr. Liu summed up the situation by saying that "we're struggling...to decrease the frequency of infections in the hospital or healthcare setting, especially multiply resistant organisms...so we're more than willing to look at innovative ways of protecting our patients."

Funding for various aspects of this or related studies was provided by Technology Development at Separator System, Kogyo and by Miyoshino Seiyaku Co., Ltd. Dr. Abraham reports being a consultant to a company that promotes the product. Dr. Liu reports serving on speakers bureaus of Forest Laboratories and Daiichi Sankyo.

15th International Congress on Infectious Diseases (ICID): Abstract 54.001. Presented June 16, 2012.

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