Bacteria incriminated by their odour

Researchers in Taiwan and the US have developed a device that uses the volatile organic compounds released by bacteria to identify the bacteria as they are cultured. When fully developed, this single-step gadget could trump the speed of current clinical techniques.

Sepsis and other bloodstream infections are very dangerous and need immediate treatment. It is therefore essential to detect microorganisms in human blood quickly to decide the most effective treatment.

Blood cultures are currently used to detect if bacteria are present in a patient’s blood. This takes 24 hours or more just to reveal if a sample contains bacteria. Further tests reveal the identity of the bacteria and show which antibiotics can kill them. This multi-step process can take several days, and in the meantime patients are often treated with antibiotics presumptively, which can induce side effects in the patient as well as antibiotic resistance in the bacteria.

The device, devised by James Carey at the National University of Kaohsiung and colleagues, can simultaneously detect and identify microorganisms. It uses a colorimetric sensing array attached to a bottle where the sample is cultured. Each bacterial species releases different mixtures of volatile organic compounds during their growth and 36 chemical dyes present on the array change colour based on the gases released. Chemometric analysis of these colour changes reveals which strain of bacteria is present.

Chemometric analysis of colour changes reveals which strain of bacteria is present

Carey says the device will save lives since it can tell the type of bacteria present in blood in the same time it takes clinicians to find if bacteria are even present. However, the system does not work if more than one species is present and does not directly show the antibiotics needed for treatment.

‘This [device] works in a single step and can detect and identify microorganisms in liquid media, which can change a clinical diagnosis,’ says Sung Lim a colorimetric sensor array specialist at Specific Technologies in California, US. He adds that it should be tested on more bacterial types to demonstrate its high sensitivity and selectivity.

The authors now plan to develop the device to work on real blood samples.

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