Smartphones fight killer bacteria
A combination of off-the-shelf quantum dot nanotechnology and a smartphone camera could soon allow doctors to identify antibiotic-resistant bacteria in just 40 minutes, potentially saving patient lives, Australian scientists believe.
Their findings were published in the journal Sensors and Actuators B: Chemical.
Staphylococcus aureus (golden staph) is a common form of bacterium that causes serious and sometimes fatal conditions such as pneumonia and heart valve infections. Of particular concern is a strain that does not respond to methicillin, the antibiotic of first resort, and is known as methicillin-resistant S. aureus, or MRSA.
The researchers said recent reports estimated that 700,000 deaths globally could be attributed to antimicrobial resistance, such as methicillin resistance. Rapid identification of MRSA was essential for effective treatment, but current methods made it a challenging process, even in well-equipped hospitals.
The researchers demonstrated a proof-of-concept device that used bacterial DNA to identify the presence of Staphylococcus aureus positively in a patient sample — and to determine if it would respond to frontline antibiotics.
They confirmed the presence of the bacterium using a mobile phone and some ultra-tiny semiconductor particles known as quantum dots.
“Our team is using synthetic biology and nanobiotechnology to address biomedical challenges,” a study author, Associate Professor Anwar Sunna, head of the Sunna Lab at Macquarie University, said.
“Rapid and simple ways of identifying the cause of infections and starting appropriate treatments are critical for treating patients effectively.
“This is true in routine clinical situations, but also in the emerging field of personalised medicine.”
The researchers’ approach identified the specific strain of golden staph by using a method called convective polymerase chain reaction (or cPCR), a derivative of a widely employed technique in which a small segment of DNA is copied thousands of times, creating multiple samples suitable for testing.
They then subjected the DNA copies to a process known as lateral flow immunoassay — a paper-based diagnostic tool used to confirm the presence or absence of a target biomarker. The researchers used probes fitted with quantum dots to detect two unique genes that confirmed the presence of methicillin resistance in golden staph.
A chemical added at the PCR stage to the DNA tested made the sample fluoresce when the genes were detected by the quantum dots — a reaction that could be captured using a mobile phone camera.
The result was a simple and rapid method of detecting the presence of the bacterium, while simultaneously ruling first-line treatment in or out, the researchers said.
Although at proof-of-concept stage, the researchers said their system, which was powered by a simple battery, was suitable for rapid detection in different settings.
“We can see this being used easily not only in hospitals, but also in GP clinics and at patient bedsides,” lead author Vinoth Kumar Rajendran, of Macquarie University, said.
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