In current laboratory practice, contaminating pathogens in urine specimens are grown in culture dishes until they can be visually identified. The major drawback of this century-old technique is the two-day time lag between specimen collection and bacteria identification.
As a result, physicians must decide whether to prescribe antibiotic therapy and, if so, which type of bacteria to treat - all without knowing the cause of the infection, if any. In contrast, the new biosensor technology would allow physicians to prescribe targeted treatment without the wait.
The study, performed by researchers at the David Geffen School of Medicine at UCLA and the Veterans Affairs Greater Los Angeles Healthcare System, used a biosensor developed by GeneFluidics to identify correctly the infection-causing gram-negative bacteria species in 98 per cent of the tested clinical urinary tract infection urine samples.
Of equal significance, the new test provided results in 45 minutes, compared to two days with conventional methods.
These results represent the first ever species-specific detection of bacteria in human clinical fluid samples using a microfabricated electrochemical sensor array.
Individual sensors on GeneFluidics' 16-sensor chips were coated with UCLA-designed species-specific genetic probes.
Clinical urine samples were directly applied to the chips and the electrochemical signal subsequently measured by GeneFluidics' multi-channel reader instrument.
The urinary tract infection pathogens were identified by examining which signals on the sensor chip were elevated. The entire experiment from sample collection to result read-out took only 45 minutes.
"Our research also showed that GeneFluidics' biosensor avoided problems inherent in alternative molecular approaches, such as PCR, that require the repeated copying of bacterial DNA or RNA prior to testing," said lead author Dr. Joseph 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."
Urinary tract infection is the most common urological disease in the United States and the most common bacterial infection of any organ system.
Urinary tract infection is a major cause of patient death and health care expenditure for all age groups, accounting for more than 7 million office visits and more than 1 million hospital admissions per year.
In the hospital, catheter associated urinary tract infection accounts for 40 per cent of all in-hospital acquired infections - more than 1 million cases each year. The total cost of urinary tract infections to the United States health care system in 2000 was approximately 3.5 billion dollars.
There is considerable interest in decreasing overall health care costs by providing smarter medicine. When laboratory-quality testing can be rapidly performed by anyone, anywhere, and the results made available in 'real-time,' tremendous improvement in patient care will be seen.
"Results were impressive for this initial 78-sample clinical study," said Bernard Churchill, chief of paediatric urology at the Clark-Morrison Children's Urological Center at UCLA and principal investigator.
"By coupling UCLA's robust probes with GeneFluidics' ultra sensitive biosensor system, we were able to identify urinary tract infection pathogens in a time frame that would enable physicians to make dramatically superior clinical decisions."
Ongoing work at UCLA and the VA Medical Center is focused on developing even better detection methods to bring the urinary tract infection biosensor chip from "bench to bedside."
At GeneFluidics, engineers are integrating the biosensors into microfluidic cartridges and building a new instrument for faster and completely automated experimentation. The team anticipates the rapid test could become available in the next two to three years.
The research is reported in the February 2006 issue of the peer-reviewed Journal of Clinical Microbiology.