Known as BARDOT (pronounced bar-DOH'), the machine scans bacteria colonies and generates a distinct black and white "fingerprint" by which they can be identified. BARDOT takes less than 24 hours to pinpoint Salmonella.
"BARDOT allows us to detect Salmonella much earlier and more easily than current methods," said
Salmonella is a major foodborne pathogen that causes salmonellosis, a type of food poisoning with symptoms of diarrhea, fever and abdominal cramps. Salmonellosis can be fatal in young children, the elderly and those with compromised immune systems.
Current Salmonella detection methods can take 72 hours to yield results and often require artificial alteration of the bacteria colonies. But the BARDOT system identifies bacteria colonies by using light to illuminate their natural characteristics, preserving the colonies for later study. The machine can be operated with minimal training and used in locations with limited resources, Bhunia said.
BARDOT, short for "bacterial rapid detection using optical scatter technology," uses a red diode laser to scan bacteria colonies on an agar plate. When the light penetrates a colony, it produces a scatter pattern, a unique arrangement of rings and spokes that resembles the iris of an eye. The pattern is matched against a library of images to identify the type of bacteria.
To test BARDOT's ability to identify Salmonella, Bhunia and his fellow researchers grew bacteria from rinses of contaminated chicken, spinach and peanut butter on agar plates for about 16 hours. After the plates were covered with tiny spherical colonies of bacteria, they placed each plate inside BARDOT - which is about the size of a large microwave oven - and scanned the colonies.
BARDOT identified Salmonella bacteria with an accuracy of 95.9 percent. It also individually distinguished eight of the most prevalent Salmonella serovars - distinct variations within a species of bacteria. Identifying a particular serovar helps trace bacteria to the original source of contamination.
"BARDOT screens quickly and inexpensively," he said. "If you get a positive result for Salmonella, you can do a follow-up test. This can help food processors make more informed decisions."
While many tools can only detect a single kind of bacteria, BARDOT picks out multiple types of disease-causing bacteria on a plate with a single scan, Bhunia said. In addition to Salmonella, BARDOT can identify Escherichia coli, Vibrio, Listeria, Bacillus and many more foodborne pathogens.
"That's the beauty of this system," Bhunia said. "It's so versatile. It can find organisms that you didn't even think about."
The paper was published in mBio and is available at http://mbio.asm.org/content/5/1/e01019-13
The research was conducted using funds from the
BARDOT is commercially available through Advanced BioImaging Systems of
Laser Optical Sensor, a Label-Free On-Plate Salmonella enterica Colony-Detection Tool
3 Bindley Bioscience Center,
We investigated the application capabilities of a laser optical sensor, BARDOT (bacterial rapid detection using optical scatter technology) to generate differentiating scatter patterns for the 20 most frequently reported serovars of Salmonella enterica. Initially, the study tested the classification ability of BARDOT by using six Salmonella serovars grown on brain heart infusion, brilliant green, xylose lysine deoxycholate, and xylose lysine tergitol 4 (XLT4) agar plates. Highly accurate discrimination (95.9%) was obtained by using scatter signatures collected from colonies grown on XLT4. Further verification used a total of 36 serovars (the top 20 plus 16) comprising 123 strains with classification precision of 88 to100%. The similarities between the optical phenotypes of strains analyzed by BARDOT were in general agreement with the genotypes analyzed by pulsed-field gel electrophoresis (PFGE). BARDOT was evaluated for the real-time detection and identification of Salmonella colonies grown from inoculated (1.2102 CFU/30g) peanut butter, chicken breast, and spinach or from naturally contaminated meat. After a sequential enrichment in buffered peptone water and modified
TNS 30TagarumaMar-140213-4636427 30TagarumaMar
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