IVD Technology
Magazine
IVDT Article Index
DoD takes delivery of biowarfare analyzer
A new weapon in the battle against biowarfare and bioterrorism was recently delivered to the U.S. Department of Defense (DoD) in the form of a rapid DNA analyzer by Cepheid Inc. (Sunnyvale, CA). According to the company, its Microfluidic Integrated DNA Analysis System (MIDAS) can identify biowarfare agents in less than 30 minutes. Along with unprecedented processing speed, MIDAS is totally automated, requiring the operator only to inject a specimen into the machine.
The new analyzer responds to DoD preparations to defend both military and civilian targets against the threat of biowarfare. Driven in part by U.S. military experience in the Middle East, which brought home the reality of biological agents as potential weapons, DoD has been actively funding research and development in this field for years. In the meantime, the number of false alarms and hoaxes involving biological agents keeps increasing. Even the hoaxes cost taxpayers millions of dollars, as quarantine and prophylactic measures must be taken no matter how unlikely the threat. One contributor to these costs is the fact that culture assays are still the gold standard for identification—and they can take days to provide definite results.
By contrast, MIDAS uses rapid PCR technology and a fluorescent detection method in a computer-controlled microfluidics circuit. Normally, PCR requires repeated cycles of heating and cooling to amplify the DNA reaction mixture. With microscale volumes, thermal cycling can be accomplished much more rapidly because of the reduced thermal inertia of the sample. In MIDAS, enough DNA for testing can be generated in 15 to 25 minutes, compared with approximately 90 minutes using conventional PCR instruments. MIDAS performs all the complicated handling of reagents and samples; amplifies the DNA; and detects specific sequences of viruses, bacteria, or spores. The system then cleans and decontaminates itself and is ready for another assay.
To detect biowarfare agents, the U.S. Army is now using a vehicular platform called the biological integrated detection system (BIDS). "BIDS is a microbiology lab housed on the back of a Humvee that drives around and sniffs the air for biological agents," notes Cepheid president Kurt Petersen. However, the current version of BIDS uses standard, manually operated microbiology instruments employing immunoassays and flow cytometry. "MIDAS is the first prototype designed to automatically detect biowarfare organisms using DNA-based assays. Hopefully, a production version of MIDAS will be deployed in the next-generation BIDS vehicle," Petersen adds.
With MIDAS, the operator needs to load different lysing, primer, and detection reagents, depending on the pathogen in question. The commercial successor to MIDAS, called Genexpert, uses the same microfluidics technology integrated into disposable assay cartridges. The cartridges contain all the specific reagents required to detect a disease organism such as anthrax, clamydia, gonorrhea, or food pathogens. In addition, the Genexpert system incorporates other advances in sample preparation, making it possible to quickly identify anthrax bacteria in a sample. "Anthrax spores are tough to lyse," explains Petersen. "Traditional methods take hours. We've developed a way to lyse anthrax spores in 30 seconds." The system's first demonstration is an assay that can detect chlamydia or gonorrhea from a 5-ml urine sample in less than 30 minutes. The fully automated system only requires the operator to inject the sample and press a button. "This is the first time such a complex DNA-probe assay has been accomplished so quickly, from sample preparation through PCR, using fluorescent detection," says Petersen.
Although heavily funded by DoD, commercial applications of Cepheid's technology abound in agriculture, medical diagnostics, and law enforcement. Petersen envisions portable instruments that can be used to detect fungus in wheat fields or salmonella in chicken farms. The Smartcycler, an even smaller model dubbed "PCR in a briefcase," has already been shipped to the military for evaluation. It can be used in a variety of field detection scenarios. —Gary Woo
Photo courtesy of William Taufic/The Stock Market
