Sniffing-out smell of disease in feces: 'Electronic nose' for rapid detection of Clostridum difficile infection

This image depicts from lef to right Dr Martha Clokie, Professor Andy Ellis and Professor Paul Monks from the University of Leicester with the mass spectrometer. Credit: University of Leicester

A fast-sensitive "electronic-nose" for sniffing the highly infectious bacteria C-diff, that causes diarrhea, temperature and stomach cramps, has been developed by a team at the University of Leicester.

Using a mass spectrometer, the research team has demonstrated that it is possible to identify the unique 'smell' of C-diff which would lead to rapid diagnosis of the condition.

What is more, the Leicester team say it could be possible to identify different strains of the disease simply from their smell -- a chemical fingerprint -- helping medics to target the particular condition.

The research is published on-line in the journal Metabolomics.

Professor Paul Monks, from the Department of Chemistry, said: "The rapid detection and identification of the bug Clostridium difficile (often known as C-diff) is a primary concern in healthcare facilities. Rapid and accurate diagnoses are important to reduce Clostridum difficile infections, as well as to provide the right treatment to infected patients.

"Delayed treatment and inappropriate antibiotics not only cause high morbidity and mortality, but also add costs to the healthcare system through lost bed days. Different strains of C. difficile can cause different symptoms and may need to be treated differently so a test that could determine not only an infection, but what type of infection could lead to new treatment options."

The new published research from the University of Leicester has shown that is possible to 'sniff' the infection for rapid detection of Clostridium difficile. The team have measured the Volatile Organic Compounds (VOCs) given out by different of strains of Clostridium difficile and have shown that many of them have a unique "smell." In particular, different strains show different chemical fingerprints which are detected by a mass spectrometer.

The work was a collaboration between University chemists who developed the "electronic-nose" for sniffing volatiles and a colleague in microbiology who has a large collection of well characterised strains of Clostridium difficile.

The work suggests that the detection of the chemical fingerprint may allow for a rapid means of identifying C. difficile infection, as well as providing markers for the way the different strains grow.

Professor Monks added: "Our approach may lead to a rapid clinical diagnostic test based on the VOCs released from faecal samples of patients infected with C. difficile. We do not underestimate the challenges in sampling and attributing C. difficile VOCs from fecal samples."

Dr Martha Clokie, from the Department of Microbiology and Immunology, added: "Current tests for C. difficile don't generally give strain information -- this test could allow doctors to see what strain was causing the illness and allow doctors to tailor their treatment."

Professor Andy Ellis, from the Department of Chemistry, said: "This work shows great promise. The different strains of C-diff have significantly different chemical fingerprints and with further research we would hope to be able to develop a reliable and almost instantaneous tool for detecting a specific strain, even if present in very small quantities."

Source: University of Leicester

How llamas' unusual antibodies might help in the fight against HIV/AIDS

Llamas contribute to the fight against AIDS. Credit: Nika Stropakke, CC-BY

Most vaccines work by inducing an immune response characterized by neutralizing antibodies against the respective pathogen. An effective HIV vaccine has remained elusive so far, but researchers have continued to make progress, often employing innovative methods. A study published on December 18th in PLOS Pathogens reports that a combination of antibodies from llamas can neutralize (destroy) a wide range of circulating HIV viruses.

After initial disappointment that HIV vaccine candidates were unable to elicit neutralizing antibodies, researchers found that some HIV-infected individuals did produce such antibodies. The current challenge is therefore to find safe and effective vaccine formulations (as opposed to HIV infection) that trigger the development of neutralizing antibodies that can recognize and prevent infection with all or most circulating HIV subtypes.

Many known neutralizing antibodies are directed against a specific part of the virus that binds to the CD4 receptor on the human target cells, and structural biology studies indicated that the site is a narrow groove. Antibodies in most mammals are relatively large proteins made up of two copies of two different individual parts (or chains), and bulkiness might be one reason why neutralizing antibodies are rare. Llamas are a notable exception: besides the common four-chain antibodies they also produce smaller ones made up of only two of the four chains. Robin Weiss, an HIV expert, and Theo Verrips, a llama antibody expert, therefore started working with this unconventional research animal.

Laura McCoy (working with Weiss at University College London, UK) led an international group of researchers to test immunization protocols and the resulting immune response in llamas. Having previously identified one particular HIV neutralizing llama antibody, for this study the researchers immunized two additional llamas and identified a total of three new neutralizing antibodies. The four HIV neutralizing llama antibodies target different parts of the CD4-binding site of the virus, and the researchers could show that when used in combination, rather than interfering with each other, they are more potent and can neutralize all of the 60 different HIV strains tested.

To understand how the llama immunization--which included two sets of four sequential vaccine injections per animal--worked, the researchers sequenced many copies of antibody-coding genes from blood cells collected after the first set of immunizations and after a further four rounds of vaccination. They also looked at the "naïve" antibody repertoire from seven llamas that had not been vaccinated. The results suggest that the neutralizing antibodies were not part of the pre-immunization repertoire, nor were they detectable after the first vaccination round. Rather, they were generated as immune cells repeatedly encountered the vaccine and responded by maturing specific antibodies that can recognize it.

While it is encouraging that broadly neutralizing antibodies were found in all of the immunized llamas, they are present only at low concentrations in the blood, and so fail to meet the goal for a protective HIV vaccine. Nonetheless, the researchers conclude that the llama model has allowed them to examine the generation of four broadly neutralizing antibodies induced by vaccination, which has not been possible in any other species.

Source: PLOS.