Tips from the Journals of the American Society for Microbiology

05/14/04

SILVER AND UV RADIATION COMBINED MAY PROVE MORE EFFECTIVE AT DISINFECTING WATER SYSTEMS

Silver and UV radiation combined may be more effective and timely at disinfecting drinking water and wastewater say researchers from the U.S. Military Academy, West Point, New York. Their findings appear in the May 2004 issue of the journal Applied and Environmental Microbiology.

Commonly used as a co-disinfectant in swimming pools and hospital hot water systems since the mid-1800's, silver has been somewhat effective at bactericidal activity with little or no harmful side effects in humans. However, researchers have found that there are organisms resistant to silver and that lengthy exposure time is necessary for disinfection to occur. Ultra-violet (UV) radiation is a more recently developed method shown to inactivate protozoa in water. The main concern associated with UV radiation is elevated cost due to extended operation periods.

In the study, coliphage MS-2, considered to be a practical surrogate for pathogenic viruses, was exposed to silver individually and then combined with UV radiation. Results showed that when exposed to only silver for ten minutes little inactivation occurred, but ten minute exposure time to silver followed by UV radiation resulted in a disinfectant rate of 99.5 %. The silver/UV radiation combination appears to minimize exposure time and operation costs while achieving maximum inactivation of the virus.

"The data clearly shows that there is a synergistic effect when silver and UV radiation are combined," say the researchers. "Because it has also been reported for a DNA virus, it is expected that the synergistic effect between silver and UV radiation might also exist for the inactivation of pathogenic viruses such as poliovirus, noroviruses, and the enteric adenovirus types."

(M.A. Butkus, M.P. Labare, J.A. Starke, K. Moon, M. Talbot. 2004. Use of aqueous silver to enhance inactivation of coliophage ms-2 by UV disinfection. Applied and Environmental Microbiology, 70. 5: 2848-2853.)


NEW METHOD MAY DETECT SARS VIRUS IN MINUTES

Japanese and Vietnamese researchers have developed a new one-step method that may allow for rapid detection of the SARS virus. Their findings appear in the May 2004 issue of the Journal of Clinical Microbiology.

"Currently, there are no suitable antiviral drugs or an effective vaccine for SARS virus. Rapid laboratory confirmation of SARS-CoV infection is therefore important for managing patient care and for preventing nosocomial transmission," say the researchers.

In the study, throat and nasal samples were collected from hospitalized patients in Vietnam. Researchers then tested for the SARS virus using a new one-step method, Loop-Mediated Isothermal Amplification (LAMP), during which DNA amplification occurs in a single tube placed under isothermal conditions (63 degrees Celsius) providing results any where from eleven minutes to one hour. This highly specific and selective method proved 87 to 100 percent effective in detecting the SARS virus in the samples collected.

"The one-step single-tube accelerated real-time quantitative RT-LAMP assay developed in this study is simple, rapid, and cost effective as well as highly sensitive and specific," say the researchers. "This has potential usefulness for clinical diagnosis and surveillance of SARS virus in developing countries, as it does not require the use of sophisticated equipment or skilled personnel."

(H.T. Cam Thai, M.Q. Le, C.D. Vuong, M. Parida, H. Minekawa, T. Notomi, F. Hasebe, K. Morita. 2004. Development and evaluation of a novel loop-mediated isothermal amplification method for rapid detection of severe acute respiratory syndrome coronavirus. Journal of Clinical Microbiology, 42. 5: 1956-1961.)

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