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Antimicrobial activity of Copper

Copper ion exerts antimicrobial effect on various types of bacteria

Copper ion’s oligodynamic action of metal can kill bacteria. The Japan Copper Development Association has been engaged in a variety of demonstration tests to scientifically demonstrate copper’s antimicrobial effect.
Here are some examples of demonstrated copper’s antimicrobial activities.

Antimicrobial effect against bacteria and virus

Highly effective against O157 / O-157

In 1996, an aggressive O157 outbreak occurred, which resulted in a large drop in sales in the food service industry. Testing has demonstrated copper’s effects against O157.
In the tests, bacteria were cultured and observed in glass dishes in which 3 cm piece copper or brass plate was placed over agar containing O157. As a result, bacteria around the copper and brass plate were prevented from reproducing. The test also revealed that no bacteria had grown directly under the plate.
O157 is transmitted to humans throughout any season through ordinary food. We must not forget the danger of O157.

Antimicrobial property testing of copper plate

Test conducted with cooperation from Institute for Food & Environmental Science, Incorporated Foundation Tokyo Kenbikyo-in Institute for Food & Environmental Science

Inactivation effects against flu and norovirus / Virus

Influenza A virus was brought into contact with a copper plated surface and the number of infections was then counted across time. As a result, about 75% of the virus was killed in one hour, and the count was reduced to 0.025% in six hours.
Moreover, it has been proved recently that copper is effective in deactivating norovirus (tested using feline calicivirus, a surrogate for norovirus).

Inactivation effects against flu and norovirus

Antimicrobial effect against the deadly Legionella / Legionella

More recently, public attention has been drawn to reports that people infected with Legionella in public bathhouses and spa facilities had died.
Legionella is a type of bacteria commonly found living in soil and water in nature, and it is contracted from water in circulation style bathtubs and hot water supply systems, and compost. Antimicrobial property testing of copper against Legionella was conducted.
There were two types of tests. The first test examined copper’s antimicrobial effect: Legionella was spread on plates of copper, stainless steel, and PVC used for water pipes, and the bacteria count was then measured on respective surfaces after culture. As a result, the 500,000 to 600,000 CFU* of bacteria on each test piece was reduced to less than 1,000 CFU on the copper plate. On the other hand, almost no reductions of bacteria count occurred on either the stainless steel or the PVC plates.
In the second test, the relationship between copper ion concentration and action time was examined. Legionella was placed in a copper ion solution with different concentration levels, and the bacteria generated were then measured. The result shows that the antimicrobial effect increases in proportion to copper ion concentration and action time.
These tests demonstrated that copper has an excellent antimicrobial effect against Legionella.

Antimicrobial property testing of copper ion solution

                                  Test conducted with cooperation from Kitasato Research Center for Environmental Science
                                                             *CFU…Colony Forming Unit the amount of bacteria presents as a group

Antimicrobial effect against cryptosporidium / Cryptosporidium

Have you ever heard of “cryptosporidium?” Cryptosporidium is a pathogenic microorganism that infects through the water and contact with human hands. It causes severe stomachaches and diarrhea. In recent years, cryptosporidium has infected large groups of people, and has become a problem in Japan.
This microorganism is greatly feared because it has a high tolerance to chlorine and cannot be killed by chlorination of tap water. The Japan Copper Development Association has conducted tests to determine copper’s antimicrobial effect against cryptosporidium.
The test results have shown that copper ion could cause the deformation and destruction of oocyst (hard cyst that covers cryptosporidium) of cryptosporidium. When copper ion-treated oocysts were transmitted to mice, the infectivity of cryptosporidium was inactivated.
Although this experiment is still in a trial status, we are planning to put the test results to practical use.

Test conducted with cooperation from Kitasato Research Center for Environmental Science

A significant effect on heterotrophic bacteria

Water running through supply pipes contains bacteria that slowly increase in a nutrient-poor culture medium (heterotrophic bacteria). Although these bacteria are not detectable under conventional culture conditions, it has been found that, if left to flourish, they lead to the proliferation of pathogens that eventually cause “opportunistic infections.” This is a serious problem in hospitals where many patients are prone to opportunistic infections. We took notice of antimicrobial activity of a copper water supply pipe, and compared it with other plastic pipes to see if the copper pipe could be effective against heterotrophic bacteria proliferation in the tap water. Results show that, given time, heterotrophic bacteria proliferated in a variety of plastic piping filled with tap water, whereas in copper piping they continuously decreased, reducing to one-hundredth of the original concentration in seven days. This proves that copper pipe can inhibit the growth of heterotrophic bacteria in tap water.

Copper water supply pipe’s antimicrobial effect against heterotrophic bacteriaTest conducted with cooperation from Kitasato Research Center for Environmental Science

Excellent antimicrobial power of copper pipe / Effective for tap water

Copper piping is used for water and hot water supply pipes installed in many high-rise buildings, apartments, and general housing to maintain living standards. Copper piping which is used in many countries around the world has many superior characteristics, including quake resistance, economic efficiency, and recyclability. In addition, copper pipes can be kept in a clean and hygienic state because of copper’s antimicrobial effect. Like copper pipe’s antimicrobial effect against cryptosporidium and heterotrophic bacteria already mentioned in previous pages, the same effect against coliform has been demonstrated through testing involving the use of seven different types of piping materials: Copper pipe, PVC lined steel pipe, stainless steel pipe, polyethylene pipe, cross-linked polyethylene pipe, hard PVC pipe, and polybutene pipe. A solution containing coliform was injected into respective pipes, which were inspected every few hours. The test results show that the copper pipe helped lower coliform count, whereas the same effect was not observed in other types of piping. In view of these results, it has been demonstrated that copper pipe has an excellent antimicrobial property compared to other types of metal and plastic piping materials. Copper benefits the tap water we use daily to keep our living healthy and hygienic.

  • Test results of piping materials’ antimicrobial effect against coliform
  • Excellent antimicrobial power of copper pipe

    As part of water quality management measures for water storage tanks, many schools started switching to a direct water supply system, which uses safe copper piping. The Japan Copper Development Association is also collaborating on this project. (Photo: Minamidaira Elementary School in Hino City, Tokyo)

Copper preserves environment and ecosystem / Limnoperna fortune

The “Limnoperna fortune” has been a major nuisance to water utilization facilities, such as agricultural irrigation systems and hydroelectric plants. This alien species, native to China, is 2 to 3 cm in length. Although each shell is small, when generated in large numbers, they clog up pipes, requiring considerable amounts of time and expense for removal. Together with the Central Research Institute of Electric Power Industry, the Japan Copper Development Association conducted tests to see if copper’s antimicrobial activity is effective in preventing adhesion of the Limnoperna fortune to pipes.
The test was conducted at Oshio Reservoir in Gunma Prefecture, where Limnoperna fortune was confirmed to be present in 2005. With the cooperation of the Kaburagawa Land Improvement District, the organization responsible for supervising the reservoir, water was pumped from the reservoir through copper, stainless steel, and PVC pipes, respectively, under identical conditions. Limnoperna fortune adherence was then observed and compared among the piping across a time span of one year.
The results show that large amounts of Limnoperna fortune and sea moss adhered to both PVC and stainless steel pipes, but almost none to the copper pipe. Based on these test results, copper is now used in water utilization facilities piping, and also as the end piece of protective pipes to prevent damage and malfunctions in water content control sensors and fixtures. In this way, an effective application and practical use of copper has been examined and promoted to handle the Limnoperna fortune-induced problems.

Copper preserves environment and ecosystem

Copper brings real power around us / Copper’s immediate power

Comparison with antimicrobial performance of copper door knob

Kitasato University recently presented its findings on the difference in antimicrobial performance of metal materials used for door knobs. It has been found that door knobs made of bronze and brass have extremely high antimicrobial effect when compared to door knobs made of stainless steel.

Antimicrobial effect on door knobs

Miracle power of a “copper ballpoint pen”

A test using ballpoint pens was conducted within a hospital setting.
A ballpoint pen with the copper-covered grip and an ordinary ballpoint pen were placed in the newborn nursery, and on each pen the bacterial contamination on the contact surfaces of the grip was examined. The results verified that the copper ballpoint pen has a significant antimicrobial effect against MRSA and other infections.
Also, when bacteria count on the palm of the hands which gripped a copper pipe for 30 minutes was examined, the bacteria count was found to have been reduced at a rate between 31 and 68%. These findings show that copper alloy can exert an antimicrobial effect on the surface of skin when in contact with copper.

MRSA culture results

Copper reduces the occurrence of mosquitoes / Dengue fever, Zika fever…, mosquitoes…

People are plagued with mosquitoes when summer comes. When bitten by a mosquito, the skin feels itchy. But an even more frightening thing is the infection that can be transmitted by a mosquito. Test results have shown that copper is effective in reducing the occurrence of mosquitoes.
In the test, larvae of Aedes albopictus placed in copper and glass containers were observed. All larvae in the copper container died without emerging, while 90% of larvae in the glass container emerged to become adults.

Aedes albopictus’ larval emergence rate

Next, a test was conducted outdoors to see if copper could reduce the occurrence of mosquitoes. No larvae of Aedes albopictus occurred in the experimental plot where a copper plate was placed. In the plot without a copper plate, a large number of larvae developed.
This test verified that copper is effective in reducing the occurrence of Aedes albopictus carrying the dengue and Zika virus.

  • Prevention of Saprolegniasis/gill disease for rainbow trout and salmon
  • Algae control using a copper plate for overflow weir board
  • Algal bloom control with brass fiber

A variety of antibacterial goods made of copper / Copper antibacterial goods

Today, a variety of antibacterial goods utilizing copper’s antimicrobial property are available for health-and-hygiene-conscious people.
Experience copper’s antimicrobial power in your daily life.

  • Suppresses slime and prevents clogging

    Copper triangular sink tidy and strainer

    Copper triangular sink tidy and strainer

  • Disinfection and deodorant with copper fiber and fine particles

    Antibacterial sponge and scrubber

    Antibacterial sponge and scrubber

  • Prevents mosquitoes and makes flower last

    Flower vase

    Flower vase

  • Eliminates odor and prevents athlete’s foot with copper fiber

    Socks

    Socks

  • Prevents mildew with fine particles of copper

    Pumice stone

    Pumice stone