Rapid contamination detection technology patent granted
08/01/2002
By Mark A. DeSorbo
LAGUNA HILLS, CA-For the last two years, a subsidiary of a fluid treatment and monitoring equipment maker has been secretly working on a laser-based technology that detects and identifies, in real time, potentially harmful contamination as well as deadly microbes.
Micro Imaging Tech nology, a business unit of Electropure Inc., was recently granted a patent for the rapid contamination detection technology, deemed the "MIT System." Inventors David L. Haavig and Gary Lorden feel it will be a mighty weapon in the contamination control arsenals of hospitals, food processors, drug makers and semiconductor manufacturers.
About the size of a soccer ball, the MIT System is made up of several highly sensitive photovoltaic sensors within an optical, nearly orb-like platform, where vial samples that are suspended in a liquid or gas are placed. It consists of five concentric arcs of detectors all viewing a common point at the center of curvature. A red, solid-state laser provides the incident light, and while multiple particles can pass through the laser beam at any time along the beam path, the detectors will only "see" and measure those passing through the center of the vial, says Haavig, who serves as chief scientist and general manager of Micro Imaging Technology
To identify, say E. coli or salmonella for example, filtered water is inoculated with the sample, he explains. The MIT System identifies individual microbes as they pass through the laser beam. A sample survey requires a measurement time of five to 30 minutes, depending on the pathogen concentration, to identify a statistically significant number of individual E. coli or salmonella microbes.
The system, he continues, measures scattered light intensity as particles or microbes individually pass through the beam. Its unique intensity pattern of scattered light is actually a fingerprint of the particle's size, shape and optical characteristics. By measuring the scattered light intensity at specific angles, the system can detect and differentiate objects the size of bacteria instantaneously.
Only one microbe or particle can be measured at a time, Haavig says. Consequently, the systems will identify microbes of a mixed species without degrading performance. The system requires little or no sample preparation and is quantitative and sensitive, detecting less than 50 microbes per cubic centimeter. In addition, a flow system may be developed to provide continuous monitoring for microbes and particles.
"Just because you measure one E. coli particle, it doesn't mean you have an E. coli problem," Haavig says. "If you have 50 particles per cubic centimeter in the sample vial, you'll need to conduct longer measurements. If you had 100 per cubic centimeter, that will cut your measurement time in half."
Library of contamination
The identification technique uses a "statistical classification algorithm" with a library of measured microbe scattering characteristics, which Haavig calls a "library."
"Essentially, it's a library-based device," he says. "The library that we are building is of thousands of individual particles and microbes of specific species that are analyzed to identify measured characteristics of scattered light intensity."
To identify an unknown microbe or particle after it has passed through the laser beam, the statistical classification algorithm extracts pertinent information from measured values specified by the library. Identification occurs within a few milliseconds after the particle passes through the beam. To date, accuracy is greater than 95 percent, the inventors claim.
The MIT System, Haavig says, offers a faster identification than conventional methods detection, which, in the case of food-borne pathogens, involves growing bacteria in a culture. From there, it could take days before the species is correctly identified.
That means if a food product that was sampled was, in fact, contaminated, it may have already reached the consumer by the time tests were complete.
"Food processing plants and municipal water agencies just can't shut down delivery while they wait a couple of days for test results," says Floyd Panning, president of Electropure. "Meanwhile, an unsuspecting public may have been served up a healthy dose of contaminated food or water by the time the test results are in."
In addition to drinking water and food processing, Haavig says the MIT System can most certainly find a home in hospital, semiconductor and microelectronics manufacturing, as well as pharmaceutical production settings, where contamination control is key.
"We have demonstrated fast and accurate detection of both fluid and food-borne pathogens, including E. coli, cryptosporidium, giardia, listeria and salmonella," Haavig says. "The most exciting feature of this technology is its ability to identify bacterial species in a matter of minutes, where current conventional methods may take hours, sometimes days."
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