Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New method to diagnose sepsis is faster, cheaper

19.11.2013
A new method could cut hours off the time it takes to diagnose blood infections while also eliminating the need for complicated manual processing and expensive equipment, according to a report to be published in mBio®, the online open-access journal of the American Society for Microbiology, on November 19.

The method combines a selective lysis step in which blood cells in the sample are destroyed, a centrifugation step to collect any bacteria or fungi in the sample, and a fluorescence step that analyzes the particular fingerprint of any pathogens present in the sample.


This is a graphic included with the press release.

Credit: John Walsh et al.

Tests show the method correctly identifies the species of bacteria or fungi in 96.5 % of positive blood culture samples, crucial information for doctors to provide the appropriate drugs for their patients.

"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," says co-author John Walsh of bioMérieux, Inc. in Durham, North Carolina. Patients with bloodstream infections are usually in very serious condition, says Walsh, and faster identification of the organism causing the infection can help get patients on the most effective antibiotics faster and save lives. Proper diagnosis is also important from the perspective of antibiotic stewardship: using more appropriate, targeted antibiotics reduces the risk of contributing to the spread of resistance to broad-spectrum antibiotics.

Walsh says the current standard approach to diagnosing bloodstream infections, Gram staining and overnight sub-culture followed by phenotypic ID tests, have 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.

In the technique developed by Walsh et al., a sample of positive blood culture is treated with lysis buffer to "pop" the blood cells, then transferred to a specialized optical tube. The tube is centrifuged, which drives bacteria or fungi, which are denser than the solution, down through a liquid density cushion to form a pellet at the bottom of the tube.

Then comes the intrinsic fluorescence spectroscopy (IFS): the microbial pellet is irradiated with light ranging from the deep ultraviolet to infrared, which excites certain organic molecules in the microorganisms, including 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 compared with a database of 37 of the most common known pathogens to identify the organism present.

"We're using intrinsic fluorescence to identify the microorganisms. It's an innate property of most living organisms. Because it's intrinsic, no reagents are needed for the identification step," which removes many of the opportunities for mistakes and lowers test costs, says Walsh.

Testing in a controlled laboratory study shows the method can correctly identify the species in 96.5% of all test samples, and 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. Among over a thousand samples tested, the method never gave an incorrect result as to the family level or the Gram type.

Walsh says the research and development team in Durham is actively working on automating the system with robotics to make it a fully hands-off process. Blood cultures grow in their own time, often producing a positive result at an inconvenient time of the day for clinical labs, he points out, 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," says Walsh. If a culture is positive at 2 AM, he says, 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. They hope be begin testing and evaluating the feasibility of an automated form of the system in a clinical environment within months.

Rapid ID Procedure: An overall schematic of the simple three-step process (lyse-spin-read) is given in Figures 1a-c. Briefly, a 2.0 mL sample of warm (35-37oC) positive broth is removed from the test blood culture bottle and added to 1.0 mL of warm (35-37oC) selective lysis buffer (0.45% w/v Brij-O10 in 0.3M CAPS, pH 11.7), contained in a 15 mL screw capped polypropylene tube. The mixture was vortexed for 5 seconds at maximum speed and then placed in a 35-37oC waterbath for 60 seconds. After an additional 1-2 second vortex, 1.0 mL of the lysate was removed and layered onto a single 5/16 inch diameter polypropylene ball (CIC Ball Co.) floating on the surface of 0.5 mL of a solution of 24% w/v cesium chloride + 0.005% w/v Pluronic F-108 + 10 mM HEPES, pH 7.4 contained within an optical micro-centrifuge tube. The polypropylene ball was used to control the layering process and create an undisturbed interface. The tube was sealed with a screw-cap and centrifuged for 2 minutes at 10,000 rpm at 20-25oC in a microcentrifuge with A-8-11 swing-out rotor.

mBio® is an open access online journal published by the American Society for Microbiology to make microbiology research broadly accessible. The focus of the journal is on rapid publication of cutting-edge research spanning the entire spectrum of microbiology and related fields. It can be found online at http://mbio.asm.org.

The American Society for Microbiology is the largest single life science society, composed of over 39,000 scientists and health professionals. ASM's mission is to advance the microbiological sciences as a vehicle for understanding life processes and to apply and communicate this knowledge for the improvement of health and environmental and economic well-being worldwide.

Garth Hogan | EurekAlert!
Further information:
http://www.asmusa.org
http://mbio.asm.org

More articles from Life Sciences:

nachricht Bare bones: Making bones transparent
27.04.2017 | California Institute of Technology

nachricht Link Discovered between Immune System, Brain Structure and Memory
26.04.2017 | Universität Basel

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Bare bones: Making bones transparent

27.04.2017 | Life Sciences

Study offers new theoretical approach to describing non-equilibrium phase transitions

27.04.2017 | Physics and Astronomy

From volcano's slope, NASA instrument looks sky high and to the future

27.04.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>