06:20am Wednesday 23 August 2017

Faster tests for lung infections

Cardiff scientists have developed a new diagnostic approach offering an unprecedented rapid and accurate diagnosis of lung infections in patients with cystic fibrosis – a disease affecting around 9000 people in the UK.

The breakthrough, they believe, will have a transformative impact on the life quality of the 80 to 95% of cystic fibrosis patients who will eventually die of respiratory failure caused by chronic bacterial infection of the lungs.

Knowing exactly what’s going wrong in patients’ lungs means that clinicians can begin treating infections immediately with the correct course of antibiotics, giving patients a better and quicker chance of recovery. This also has important implications for reducing multi-drug resistance caused by the unnecessary prescription of antibiotics.

People living with the cystic fibrosis are prone to lung infections made up of multiple disease-causing bacteria, such as the multi-drug resistant Pseudomonas, and unless identified and treated quickly will deteriorate rapidly.

According to the researchers – a collaborative team from Cardiff and the University Hospital of South Manchester NHS Foundation Trust – the current method for diagnosing bacterial infection, which relies on culture tests, hasn’t changed substantially in over half a century.

As well as being time-consuming and costly, they say the method is flawed and in 11% of cases fails to detect the deadly bacteria present in infection, of which there are hundreds in any given patient lung sample.

Published today in the Journal of Clinical Microbiology, the team demonstrates how a simple genetic test can rapidly identify lung infections in cystic fibrosis patients and offer a more accurate assessment of all the bacteria species present.

The new test uses DNA isolated from lung samples by a method routinely applied across the UK for diagnosis of viral infections. Using this readily available DNA in a joined-up testing approach could, researchers say, revolutionise the future of microbial infection diagnosis.

In addition, the early detection of virulent strains of bacteria is critical to containing the spread of infection in hospitals and clinics.

DNA isolated from clinical samples is already used by scientists to detect viruses, such as influenza, in public health virology laboratories. Repurposing this technique for the diagnosis of bacterial infection in cystic fibrosis patients, using gene data from patient DNA, could also be applied to other respiratory conditions such as asthma and chronic pulmonary disorder.

Professor Eshwar Mahenthiralingam, from the University’s School of Biosciences, has studied cystic fibrosis lung infections for over 20 years and is recognised as a leader in the study of problematic antibiotic resistant bacteria. He said:

“From research studies carried out over the last 10 years, we have known that lung infections in people with cystic fibrosis are caused by multiple bacteria, but routine diagnosis in public health labs still do not account for this sample diversity.

“By taking advantage of existing virology sample processing methods, and applying simple bacterial genetic tests, we can accurately diagnose infections with very problematic antibiotic-resistant bacteria.

“Better diagnosis of these infections will improve treatment, quality of life and survival for people with cystic fibrosis. These tests could feasibly be rolled out across the NHS immediately.

“The next phase of our study will seek to evaluate how well the diagnostic scheme performs in bringing standards of care benefits to people with cystic fibrosis, and will assess how much it will save in terms of costs for the NHS.”

Professor Alexander McAdam, a pathologist from Harvard University’s Boston Children’s hospital, said:

“Characterization of bacterial populations in the lungs of patients with cystic fibrosis by genetic methods will very likely be part of clinical care of these patients.

“These methods reveal more about these bacterial populations than we can readily determine using conventional culture methods. Unfortunately, most of the genetic methods are technically difficult and will be hard to use in clinical laboratories.

“This study is important because it describes a method that could be used more readily by clinical laboratories.” 

Janet Allen, Director of Research and Care at the Cystic Fibrosis Trust, said:

“The results of this study move scientists a step closer to providing a faster technique for more accurately detecting the nature of bacteria infecting the lungs of people with cystic fibrosis. 

“Cystic fibrosis makes lungs vulnerable to infections which scar and damage them and lead to a vicious circle of more infection and inflammation. On average a person with cystic fibrosis loses 2% of their lung function per year over the course of their lifetime, and they are left relying on supplementary oxygen, machines to help them breathe and eventually lung transplants.

“This development would enable clinicians to more quickly characterise the microbiome in the lung.  Furthermore, it could be extended to detect viruses and possibly explore the relationship between viral infections and bacterial infections.

“Further work is now needed to investigate how this technique can be incorporated into existing diagnostic processes.”

Cardiff University


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