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Having immediate access to not only information, but also the right information is a defining characteristic of our times. Use of the internet has made dissemination and integration of information incredibly facile, so much so that many of us expect immediate answers.
With access to this vast ocean of information, it becomes readily apparent that the specific question one asks carries extreme importance. Ask the wrong question and one will receive a barrage of useless and even misleading information.
Nowhere is this more apparent than in infectious disease diagnostic testing. Here, asking the right question not only permits identification of a deadly microbe in a specific patient, but it also appropriately arms epidemiologists giving them a fighting chance to stop a pandemic in its tracks. The diagnostic test chosen provides one with an array of information, akin to an internet search engine. But often many that ask the "right question" still run at dial-up speeds.
In the infectious disease community today there is a growing trend to get into the field truly rapid diagnostic tests that provide the right type of information in a very short time frame.
In making the upgrade to truly rapid tests, several conditions must be met. Tests must be sensitive enough to reliably detect the pathogen in question, and specific to identify the correct organism--comparable to that of traditional culture. Finally, to be labeled "rapid," a certain time-point advantage must be met--ideally 0.5 to 6 hours.
 German Outbreak
Infectious disease specialists have at their disposal a dizzying array of diagnostic tests and select from these based on the question at hand. This was elegantly illustrated most recently in the European outbreak of enterohemorrhagic E coli this spring, 2011.1
Before the outbreak, this strain of E. coli (O104:H4) was thought to have a low virulence. The strain ultimately isolated was unique in that hemolytic-uremic syndrome developed in half of those who contracted the bacterium. In total 1,600 people reported contracting the bacterium, in 16 countries including the United States.
The bacterium E. coli (O104:H4) was painstakingly studied. It was screened for the Stx gene (Shiga-toxin-producing E. coli virulence factor) by either enzyme immunoassay or polymerase chain reaction, grown on chromogenic agar to detect the extended-spectrum beta-lactamase and a routine microdilution assay was used to determine antibiotic sensitivity.
The strain responsible for this outbreak was found to be resistant to all beta-lactams and third generation cephalosporins as well as naladixic acid. However, it was found to be sensitive to carbapenems and ciprofloxacin. While identification of specific virulence factors may be done by PCR, confirmation of a pathogen's susceptibility to a specific antibiotic did not currently lie in the realm of the rapid test modalities used in this outbreak.
The German outbreak of O104:H4 is an example of a pathogen responding to selective pressure after being exposed to countless antibiotics. We see this trend in multi-drug resistant gonorrhea as well as extremely drug-resistant TB.2
Identify and Treat
The real fear is that in future years, we will see more and more of these superbugs cropping up in a wide variety of regions around the world. The clock cannot be turned back with regards to antibiotic resistance, but developments today can make us better prepared to identify and treat the bacteria and viruses once they are detected with specific and targeted drugs.
As traditional culture still takes between 2-5 days to return results, the quest for more rapid diagnostics has depended largely on the promise of DNA analysis and real-time PCR protocol.
Although labeled as rapid diagnostic tests (RDTs), it has been shown that these tests are not actually rapid at all. Even though DNA analysis can run a test in 5 minutes, that doesn't mean that from start to finish, this diagnostic process takes only 5 minutes.
In fact, many PCR tests require an enrichment process of the sample at least overnight. This significantly slows the test down. While some success has been found in using DNA analysis for detecting viruses like influenza and HIV, the method has not proven to be the holy grail the industry desperately needs.
To win against today's superbugs, laboratories and hospitals must have access to fast tests that are simple to use and cost effective. Several emerging technologies are tackling this challenge head on, such as those from NanoLogix, Atlas Genetics, and a novel approach by the University of Georgia (see the side bar for more).
These technologies are redefining the meaning of the word rapid in the diagnostic setting, by providing legitimately fast and accurate test results. By being truly rapid in their delivery of diagnostic results, these companies are answering the demands of the infectious disease community and providing real-time options for those on the front lines of the fight against some of nature's deadliest pathogens. In the age of instant access to an unlimited amount of information, these tests offer the potential of delivering rapid results that we will depend on when we need the right answers fast.
Dr. Jonathon Faro is chief resident in Obstetrics and Gynecology; and the director of the 300 patient Group B Strep clinical trial at the University of Texas Health Science Center. Dr. Sebastian Faro is chief of Obstetrics and Gynecology at LBJ Hospital, Houston.
Technology
NanoLogix
Based in Hubbard, OH, this emerging biotech company has developed a method for viewing live micro colonies 4-12 times faster than PCR or conventional culturing. The technology detects micro colonies in a sample, identifies the microorganisms being targeted and also provides results on the antibiotic sensitivity all within a matter of 4-6 hours depending on the microorganism being tested.
"People knew for decades that microcolonies would be present in culture, but there was no way to transfer them or stain them in a way to make them visible," said Nanologix CEO Bret Barnhizer.
The company technology is based on a nanopore membrane sandwiched between two layers of agar. Microorganisms grow on this membrane layer for a fraction of the time conventional culturing requires and allows for the transport of the still invisible micro colonies to a staining plate. After only a few minutes on this staining plate, the micro colonies are detectable.
Additional filtration and washing steps identify target bacteria and reveal antibiotic sensitivity. "We don't make anything grow any faster," Barnhizer continued, "the membrane provides the ability for people to see what's growing much faster." Trial results of the technology were published in the American Journal of Perinatology. (Source: Nanologix)
Atlas Genetics
The point-of-care (POC) diagnostics offers health professionals the ability to test for medical conditions at the site of patient care. Atlas has developed a flexible POC technology platform, called Velox, which has been designed to accurately and quickly diagnose a wide range of medical conditions within a 30-minute time frame.
The Velox system consists of an inexpensive test machine into which a disposable card containing a patient sample is inserted. Atlas is developing tests for a range of infectious diseases including hospital acquired infections, sexually transmitted diseases and meningitis. The platform is scheduled to launch within Europe by the end of 2012, followed by rollout in the United States, pending regulatory approvals. (Source: Atlas Genetics)
Detecting Influenza With Gold
Researchers at the University of Georgia College of Veterinary Medicine have published a paper in the August 2011 edition of the journal Analyst that describes a new method for rapidly detecting influenza virus.4 By coating gold nanoparticles with antibodies that bind to specific strains of the flu virus and then measuring how the particles scatter laser light, the technology can detect influenza in minutes at a cost of only a fraction of a penny per exam.
"We've known for a long time that you can use antibodies to capture viruses and that nanoparticles have different traits based on their size," said study co-author Ralph Tripp, Georgia Research Alliance Eminent Scholar in Vaccine Development in the UGA College of Veterinary Medicine. "What we've done is combine the two to create a diagnostic test that is rapid and highly sensitive."5
References
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Frank C, Werber D, Cramer J, et al. Epidemic profile of Shiga-Toxin-Producing Escherichia coli O104:H4 outbreak in Germany-preliminary report. New Eng J Med. June 2011, Epub ahead of print.
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Ohnishi M, Golparian D, Shimuta K, et al. Is Neisseria gonorrhea initiating a future era of untreatable gonorrhea? Detailed characterization of the first strain with high-level resistance to ceftriaxone. Antimicrob Agents and Chemother, 2011(55):3538-45.
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Faro J, Katz A, Bishop K, et al. Rapid Diagnostic Test for Identifying Group B Streptococcus. American Journal of Perinatology 2011, Epub ahead of print.
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Driskell JD, Jones CA, Tompkins SM, Tripp RA. One-step assay for detecting influenza virus using dynamic light scattering and gold nanoparticles. Analyst; (15):136.
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