EVERY day, doctors prescribe antibiotics based on an educated guess about which bugs are causing the symptoms they see before them. Sometimes they guess wrong and it can take days or even weeks for tests to identify the true culprits. In the meantime, people are taking ineffective drugs, contributing to the growing problem of antibiotic resistance.
A solution could come in the shape of a machine capable of identifying all bacteria, viruses and fungi known to cause infectious disease in humans. Tests of the PLEX-ID universal biosensor suggest it is more accurate than the standard method, which involves growing the offending pathogen in a dish and then identifying it by its shape and characteristics.
The device, developed by US pharmaceutical company Abbott, combines and adapts two existing techniques. Microbe samples from fluids such as saliva and blood are processed to isolate the genetic material. Regions of this DNA are selected according to their likely origin and copied, using a common process called a polymerase chain reaction (PCR). These DNA fragments are then effectively weighed by passing them through a sophisticated mass spectrometry device.
From this, the composition of base pairs A, G, C and T - the chemical building blocks of DNA - can be calculated. Cross-checking base pair compositions for multiple DNA regions against a database of genetic "fingerprints" of known microbes reveals the bug's identity. A repeatedly blank result suggests the microbe is new, and one whose profile matches some DNA regions but not all implies that a known microbe has mutated.
PLEX-ID has been used for research purposes for several years, with early work focused on identifying potential biological warfare agents. In 2003, an earlier model correctly identified a new kind of coronavirus as the cause of SARS, and six years later, it was used to identify the first two cases of H1N1 swine flu in the US.
The existing version identifies microbes in 8 hours. If the smaller version currently in development can do so within 5 hours as planned, it could allow doctors to wait for an accurate diagnosis before prescribing treatment.
In most cases, taking ineffective antibiotics while waiting for a definitive diagnosis doesn't harm people, because their immune systems tackle the bugs anyway. It can, however, be fatal for those with impaired immunity, says Mark Wilcox at the University of Leeds in the UK, a member of one of several independent groups evaluating the device for clinical use.
Wilcox presented preliminary findings from his group's analysis at a Society for Applied Microbiology meeting in London last month. They found that PLEX-ID outperformed a culture-based approach in identifying the bacterial and fungal pathogens in 250 human tissue and fluid samples. Other tests suggested that the device is also more sensitive than sequencing small regions of the genome to identify the microbe.
"Currently we can only look for the known knowns," says Andrew Sails of the Health Protection Agency public health lab in Newcastle, UK. "The advantage with this kind of technology is that it can look for the known unknowns and the unknown unknowns."
Sails cautioned that the time taken for PLEX-ID to generate results might be longer than claimed because of the practicalities of transporting samples to labs and processing them in large numbers.
In the print version of this article, the second paragraph included the phrasing, "Tests of the PLEX-ID universal biosensor suggest it is even more accurate than the standard method?". This has been edited here.
This article appeared in print under the headline "Caught something nasty? Find out double quick"
If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.
Have your say
Only subscribers may leave comments on this article. Please log in.
Only personal subscribers may leave comments on this article
Subscribe now to comment.
All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.
If you are having a technical problem posting a comment, please contact technical support.
santorum drops out bby zimmerman website miami marlins marlins marlins facebook buys instagram
No comments:
Post a Comment
Note: Only a member of this blog may post a comment.