The following release is a summary of a presentation at the 100th General Meeting of the American Society for Microbiology. Additional information on this and other presentations can be found in the General Meeting Press Kit online at http://www.asmusa.org/pcsrc/gm2000/presskit.htm.
Embargo Date/Time: Monday, May 22, 1:00 p.m.
Primary Author:
C. William Keevil, CAMR
44 1980 612310
[email protected]
A recent study has found that three independent factors (i.e., water temperature, water hardness, and type of piping material) affect survivability of the highly toxic E. coli O157:H7 strain of bacteria in drinking water systems. This dangerous pathogen is known to many as the "burger bug" because of its association with eating contaminated undercooked beef burgers. However, there have also been serious outbreaks of infection caused by drinking contaminated water. Regarding material selection, it was concluded that copper water pipes may have significant antibacterial advantages over polybutylene plastic and stainless steel. In every temperature range and water hardness condition studied, copper demonstrated significant antibacterial advantages over plastic. And in all of the conditions studied, copper demonstrated either stronger or equivalent antibacterial properties compared to stainless steel.
The work was funded by the International Copper Association, New York and led by Dr Bill Keevil, while at the Centre for Applied Microbiology and Research (CAMR) in England. His co-workers were Dr James Walker and Dr Andrew Maule. The results of the study were presented during the American Society of Microbiology 100th General Meeting held May 21-25 in Los Angeles.
The team found that in soft water systems at 100C, the concentration of toxic E. coli O157 was over 100 times lower on copper substrates than on steel and plastic substrates. These temperature and water hardness conditions are typical of many residential wells and potable surface water supplies around the world. At warm temperatures (200C) in soft water, the antibacterial effect of copper is more than 10 times greater than plastic or stainless steel. The experiments indicated that when used with cool soft drinking water resources, copper water piping systems have the potential to reduce the risk of human infection from E. coli O157 bacteria.
The study also found that copper has strong anti-biofouling characteristics in cool (100C) soft waters whereas biofouling was very significant on plastic and steel. After being submerged for seven days in cool soft waters, little biofilm slime was detected on the copper surfaces. However, nearly 80% of the steel surfaces and 90% of the plastic surfaces were covered with slimes. "Biofilms are harbingers of E. coli O157 and other microbial pathogens and they pose a significant risk to human health," said Keevil. "Copper was the only piping system examined that exhibits strong anti-biofouling characteristics for cool (100C) soft water drinking supplies."
For potable systems with moderately hard water, copper imparts very strong anti-biofouling advantages over plastic at 100C (cool water), 200C (warm water), and 400C (hot water). Biofilm coverage in moderately hard water ranged from 25-43% on plastic substrates whereas biofilm coverage on copper substrates at all water temperatures was less than 2%.
For potable systems with hard water, piping materials seem to play a much lesser role in preventing biofouling, presumably because the calcium carbonate deposits in the materials from the water prevent copper from contacting the bacteria directly.
An associated study by the team found that toxic E. coli O157 bacteria also survive for much shorter periods of time in dried deposits on copper and brass surfaces (a few hours) than on stainless steel (several weeks). This finding has wide-ranging implications for reducing outbreaks from cross contamination of E. coli in the food processing industry.
About Escherichia coli (E. coli) O157
E. coli O157 is a highly infectious ACDP Hazard Group 3 foodborne and waterborne pathogen that has created a serious public health challenge for the food processing industry. This strain of bacteria produces potent verocytotoxins, which can cause hemolytic colitis, hemolytic uremic syndrome (kidney disease), and even death. Fecal contamination from the intestines of cattle and sheep is one of the most prevalent pathways for infection.
E. coli O157 bacteria infect tens of thousands of people around the world every year. An outbreak in Japan caused 9,000 people to become sick. A 1997 outbreak in Scotland was responsible for 500 infections and 20 deaths. And in the U.S., over 500 people became ill and three children died after eating undercooked hamburgers infected with E. coli O157. The largest waterborne outbreak occurred at the Washington County Fairground near Albany, New York State in 1999. Over 1000 people were infected, 65 were hospitalised and 2 died. Nine children were very poorly due to developing haemolytic uraemic syndrome and required long-term dialysis.
It is believed that just ten to fifty highly toxic E. coli O157 organisms are sufficient to infect humans with illness. The infections are difficult to treat and antibiotics may prompt the bacteria to release even more verocytotoxins. In healthy individuals, E. coli O157 infections usually last three to five days. However, the bacteria can victimize children under 14 years of age, the elderly, and immunocompromised individuals with serious complications.
###
RSS