A sensor chip coated with species-specific genetic probes is placed in a multichannel reader instrument that measures electrical currents coming from sensors on the chip that detect bacteria.
Accounting for more than 7 million trips to the doctor’s office each year, urinary tract infections (UTIs) afflict an estimated 40% of women and 12% of men at least once during their lifetime, according to the American Urological Association. Though the infections are easily cured with antibiotics, diagnosis requires a lengthy bacterial identification process that can compromise patient care. However, the development of DNA biosensors may enable specific bacteria identification in as little as 45 minutes.
A microfabricated electrochemical sensor array developed by GeneFluidics (Monterey Park, CA; www.genefluidics.com) correctly identified the gram-negative bacteria in 98% of UTI-tainted urine samples. The results of the study, conducted by the David Geffen School of Medicine at UCLA and the Veterans Affairs Greater Los Angeles Healthcare System, mark the first species-specific detection of bacteria in human fluid samples by this type of instrument.
Currently, lab workers culture specimens until bacteria are large enough to visually identify—a process that can take 48 hours. The sensor array used in the UCLA study produced results in just 45 minutes.
These expedited results could enable physicians to prescribe targeted antibiotics. In order to alleviate patient discomfort, physicians frequently prescribe antibiotics to patients exhibiting symptoms of UTIs without knowing the specific bacteria causing the infection. If this sensor technology is adopted by the healthcare system, doctors will be able to identify the most effective antibiotic for the identified bacteria.
“Our research also showed the GeneFluidics’s biosensor avoided problems inherent in alternative molecular approaches, such as polymerase chain reaction, that require the repeated copying of bacterial DNA or RNA prior to testing,” says Joseph C. Liao, clinical instructor of urology at the David Geffen School of Medicine at UCLA. “We found that these amplification methods do not provide reproducible results.”
Researchers conducted the study by coating GeneFluidics’s 16-sensor chips with UCLA-designed species-specific genetic probes. Each sensor featured three single-layer gold electrodes and each electrode contained one representative capture probe for a bacterial urinary pathogen. Urine samples were then applied directly to the sensor chips. GeneFluidics’s multichannel reader instrument measured electrochemical signals, which enabled researchers to identify UTI pathogens by observing elevated signals on the chip.
Next on the firm’s agenda is the integration of the biosensors into microfluidic cartridges, as well as the development of a similar faster and completely automated instrument. This rapid test could be available in two to three years.
“There is considerable interest in decreasing overall healthcare costs by providing smarter medicine,” says Vincent Gau, chief executive officer of GeneFluidics. “When laboratory-quality testing can be rapidly performed by anyone, anywhere, and the results made available in real time, we will see tremendous improvement in patient care. This joint project with UCLA may spearhead that shift.”
The research for this study was published in the Journal of Clinical Microbiology’s February 2006 issue.