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for Staphylococcus infection
Credit: Bill Branson
A new technique could cut hours off the time it takes to diagnose blood infections, according to a report published in mBio.
The
method combines a selective lysis step in which blood cells are destroyed, a centrifugation step to collect any bacteria or
fungi, and a fluorescence step that reveals the “fingerprint” of any
pathogens present in the blood sample.
In tests, this method identified
the species of bacteria or fungi in 96.5% of positive blood culture
samples.
“The primary benefit of getting a rapid identification is making sure the patient is on the right [antibiotic] therapy and to quickly make any needed adjustments to the initial therapy,” said study author John Walsh, of bioMérieux, Inc. in Durham, North Carolina.
Walsh added that the current standard approach to diagnosing bloodstream infections—Gram staining and overnight sub-culture followed by phenotypic ID tests—has limitations that can prevent timely treatment.
Gram staining provides early, low-level information about the type of microorganism present, but it sometimes takes hours to deliver a result, and technicians can make mistakes in the process that provide misleading results.
Other, more specific identification methods are also available for diagnosis, but they can take at least a day or two to produce results, and many require expensive equipment.
So Walsh and his colleagues developed a new technique. With this method, a sample of positive blood culture is treated with lysis buffer, to “pop” the blood cells, then transferred to a specialized optical tube.
Next, the tube is centrifuged, which drives bacteria or fungi down through a liquid density cushion to form a pellet at the bottom of the tube.
Then comes the intrinsic fluorescence spectroscopy. The microbial pellet is irradiated with light ranging from the deep ultraviolet to infrared. This excites certain organic molecules in the microorganisms—tryptophan, NADH, FAD, porphyrins, and others—and causes them to fluoresce in a characteristic way depending on the identity of the microbe.
The exact pattern of fluorescence is then compared with a database of 37 common pathogens to identify the organism present.
“We’re using intrinsic fluorescence to identify the microorganisms,” Walsh noted. “It’s an innate property of most living organisms. Because it’s intrinsic, no reagents are needed for the identification step.”
This removes many of the opportunities for mistakes and lowers test costs, he added.
In tests, this method correctly identified the species in 96.5% of all samples. In the 2.7% of samples for which no species identity was provided, the system was able to correctly identify 67% to the family level, which is often enough information to select an effective therapy.
More than 1000 samples were tested, and the method never gave an incorrect result as to the family level or the Gram type.
Walsh and his colleagues are now working on automating this system with robotics to make it a fully hands-off process. He noted that blood cultures grow in their own time, often producing a positive result at an inconvenient time of the day for clinical labs, so automation could speed up diagnosis significantly.
“Our vision is to have a system that will automatically identify the blood culture isolate within 15 minutes of the culture being called positive,” Walsh said.
If a culture is positive at 2 am, automating this method could make it possible to identify the organism by 2:15 am and send an electronic report to a patient’s physician.
The researchers hope to begin testing and evaluating the feasibility of an automated form of the system in a clinical environment within months. 
for Staphylococcus infection
Credit: Bill Branson
A new technique could cut hours off the time it takes to diagnose blood infections, according to a report published in mBio.
The
method combines a selective lysis step in which blood cells are destroyed, a centrifugation step to collect any bacteria or
fungi, and a fluorescence step that reveals the “fingerprint” of any
pathogens present in the blood sample.
In tests, this method identified
the species of bacteria or fungi in 96.5% of positive blood culture
samples.
“The primary benefit of getting a rapid identification is making sure the patient is on the right [antibiotic] therapy and to quickly make any needed adjustments to the initial therapy,” said study author John Walsh, of bioMérieux, Inc. in Durham, North Carolina.
Walsh added that the current standard approach to diagnosing bloodstream infections—Gram staining and overnight sub-culture followed by phenotypic ID tests—has limitations that can prevent timely treatment.
Gram staining provides early, low-level information about the type of microorganism present, but it sometimes takes hours to deliver a result, and technicians can make mistakes in the process that provide misleading results.
Other, more specific identification methods are also available for diagnosis, but they can take at least a day or two to produce results, and many require expensive equipment.
So Walsh and his colleagues developed a new technique. With this method, a sample of positive blood culture is treated with lysis buffer, to “pop” the blood cells, then transferred to a specialized optical tube.
Next, the tube is centrifuged, which drives bacteria or fungi down through a liquid density cushion to form a pellet at the bottom of the tube.
Then comes the intrinsic fluorescence spectroscopy. The microbial pellet is irradiated with light ranging from the deep ultraviolet to infrared. This excites certain organic molecules in the microorganisms—tryptophan, NADH, FAD, porphyrins, and others—and causes them to fluoresce in a characteristic way depending on the identity of the microbe.
The exact pattern of fluorescence is then compared with a database of 37 common pathogens to identify the organism present.
“We’re using intrinsic fluorescence to identify the microorganisms,” Walsh noted. “It’s an innate property of most living organisms. Because it’s intrinsic, no reagents are needed for the identification step.”
This removes many of the opportunities for mistakes and lowers test costs, he added.
In tests, this method correctly identified the species in 96.5% of all samples. In the 2.7% of samples for which no species identity was provided, the system was able to correctly identify 67% to the family level, which is often enough information to select an effective therapy.
More than 1000 samples were tested, and the method never gave an incorrect result as to the family level or the Gram type.
Walsh and his colleagues are now working on automating this system with robotics to make it a fully hands-off process. He noted that blood cultures grow in their own time, often producing a positive result at an inconvenient time of the day for clinical labs, so automation could speed up diagnosis significantly.
“Our vision is to have a system that will automatically identify the blood culture isolate within 15 minutes of the culture being called positive,” Walsh said.
If a culture is positive at 2 am, automating this method could make it possible to identify the organism by 2:15 am and send an electronic report to a patient’s physician.
The researchers hope to begin testing and evaluating the feasibility of an automated form of the system in a clinical environment within months.
for Staphylococcus infection
Credit: Bill Branson
A new technique could cut hours off the time it takes to diagnose blood infections, according to a report published in mBio.
The
method combines a selective lysis step in which blood cells are destroyed, a centrifugation step to collect any bacteria or
fungi, and a fluorescence step that reveals the “fingerprint” of any
pathogens present in the blood sample.
In tests, this method identified
the species of bacteria or fungi in 96.5% of positive blood culture
samples.
“The primary benefit of getting a rapid identification is making sure the patient is on the right [antibiotic] therapy and to quickly make any needed adjustments to the initial therapy,” said study author John Walsh, of bioMérieux, Inc. in Durham, North Carolina.
Walsh added that the current standard approach to diagnosing bloodstream infections—Gram staining and overnight sub-culture followed by phenotypic ID tests—has limitations that can prevent timely treatment.
Gram staining provides early, low-level information about the type of microorganism present, but it sometimes takes hours to deliver a result, and technicians can make mistakes in the process that provide misleading results.
Other, more specific identification methods are also available for diagnosis, but they can take at least a day or two to produce results, and many require expensive equipment.
So Walsh and his colleagues developed a new technique. With this method, a sample of positive blood culture is treated with lysis buffer, to “pop” the blood cells, then transferred to a specialized optical tube.
Next, the tube is centrifuged, which drives bacteria or fungi down through a liquid density cushion to form a pellet at the bottom of the tube.
Then comes the intrinsic fluorescence spectroscopy. The microbial pellet is irradiated with light ranging from the deep ultraviolet to infrared. This excites certain organic molecules in the microorganisms—tryptophan, NADH, FAD, porphyrins, and others—and causes them to fluoresce in a characteristic way depending on the identity of the microbe.
The exact pattern of fluorescence is then compared with a database of 37 common pathogens to identify the organism present.
“We’re using intrinsic fluorescence to identify the microorganisms,” Walsh noted. “It’s an innate property of most living organisms. Because it’s intrinsic, no reagents are needed for the identification step.”
This removes many of the opportunities for mistakes and lowers test costs, he added.
In tests, this method correctly identified the species in 96.5% of all samples. In the 2.7% of samples for which no species identity was provided, the system was able to correctly identify 67% to the family level, which is often enough information to select an effective therapy.
More than 1000 samples were tested, and the method never gave an incorrect result as to the family level or the Gram type.
Walsh and his colleagues are now working on automating this system with robotics to make it a fully hands-off process. He noted that blood cultures grow in their own time, often producing a positive result at an inconvenient time of the day for clinical labs, so automation could speed up diagnosis significantly.
“Our vision is to have a system that will automatically identify the blood culture isolate within 15 minutes of the culture being called positive,” Walsh said.
If a culture is positive at 2 am, automating this method could make it possible to identify the organism by 2:15 am and send an electronic report to a patient’s physician.
The researchers hope to begin testing and evaluating the feasibility of an automated form of the system in a clinical environment within months.