Dec. 12, 2014
By Medical Discovery News
The time it takes to test for the cause of an infection ranges from minutes to weeks. A new generation of biosensors may change that, as they are being developed to identify the viral, bacterial, or fungal origin of an illness within a few hours, allowing physicians to begin the correct treatment sooner.
Many infections have symptoms that resemble the flu, such as HIV, the fungal infection coccidioidomycosis, Ebola, and even anthrax. This makes it very difficult to make a diagnosis. The emergence of new microbial pathogens such as SARS and MERS and bacterial resistance to antibiotics only adds to the fight against infectious agents. Scientists like Louis Pasteur and Robert Koch developed the traditional method for diagnosing infectious disease about 150 years ago, and modern methods have improved their discoveries.
Viruses, bacteria, and fungi have genetic information contained in DNA, RNA, or both. Each strand of DNA or RNA is made of four kinds of building blocks called nucleotides: adenine (A), cytosine (C), guanine (G), and thymine (T) in DNA or uracil (U) in RNA. Every species has a unique genetic code as seen in its arrangement of nucleotides, and by unlocking that code scientists can determine their identity. Each of the nucleotides has a different molecular weight, so the number of each nucleotide in a strand of DNA or RNA can be determined by measuring it on a device called a mass spectrometer. This can identify a microbial pathogen faster than the traditional culturing method, and can also identify those that can’t be grown in a lab.
However, the massive amount of DNA and RNA in a patient’s own cells complicates things. To tackle this problem, inventors of the new biosensor have coupled a mass spectrometer with polymerase chain reaction (PCR) to amplify any piece of genetic information that matches a known sequence from a pathogen. The sensor can then detect a very broad array of potential pathogens simultaneously.
Scientists have been very careful in selecting the unique genetic regions of various pathogens for this test. Once the PCR is used to amplify pieces of potential pathogens in the sample, the mass spectrometer spits out a series of numbers that can be cross-referenced to a database of over 1,000 pathogens that cause human disease in just a few hours.
For example, two children were hospitalized with flu-like symptoms in Southern California in 2009. They tested positive for the flu virus, but doctors did not know which strain of the flu they had. The new sensor analyzed their samples and revealed that both children were infected with H1N1, otherwise known as swine flu, which was not circulating at that time. H1N1 became a pandemic strain with cases all around the world.
This new technology represents a universal pathogen detector, capable of identifying the organism responsible for a person’s illness in just a few hours. Networking the detectors between hospitals and health departments would quickly identify outbreaks and possibly save lives.
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Pamela K. Bond 