DNA test can quickly identify pneumonia in severe COVID-19 patients

LONDON

Cambridge scientists have developed a simple DNA test that can quickly identify secondary infections in COVID-19 patients, who have double the risk of developing pneumonia while on ventilation.

Mechanical ventilation is often the only way to keep patients with the most severe forms of COVID-19 alive, as doctors use anti-inflammatory therapies to treat their inflamed lungs, the researchers said.

However, these patients are susceptible to further infections from bacteria and fungi that they may acquire while in hospital –- so called 'ventilator-associated pneumonia'.

Now, researchers at the University of Cambridge and Cambridge University Hospitals NHS Foundation Trust have developed a DNA test to quickly identify these infections and target antibiotic treatment as needed.

The test, described in the journal Critical Care, gives doctors the information they need to start treatment within hours rather than days, fine-tuning treatment as required and reducing the inappropriate use of antibiotics.

The researchers noted that this approach, based on higher throughput DNA testing, is being rolled out at Cambridge University Hospitals and offers a route towards better treatments for infection more generally.

"Early on in the pandemic we noticed that COVID-19 patients appeared to be particularly at risk of developing secondary pneumonia, and started using a rapid diagnostic test that we had developed for just such a situation," said Andrew Conway Morris from Cambridge's Department of Medicine.

"Using this test, we found that patients with COVID-19 were twice as likely to develop secondary pneumonia as other patients in the same intensive care unit," said Conway, co-author of the research.

The team noted that COVID-19 patients are thought to be at increased risk of infection for several reasons.

According to the researchers, these severe COVID-19 cases tend to spend more time on a ventilator than patients without COVID-19, due to the amount of lung damage.

Many of these patients also have a poorly-regulated immune system, where the immune cells damage the organs, but also have impaired anti-microbial functions, increasing the risk of infection, the researchers explained.

They said confirming a pneumonia diagnosis is challenging, as bacterial samples from patients need to be cultured and grown in a lab, which is time-consuming.

The new test takes an alternative approach by detecting the DNA of different pathogens, which allows for faster and more accurate testing.

The test, developed at Addenbrooke's hospital in collaboration with Public Health England, uses multiple polymerase chain reaction (PCR) which detects the DNA of the bacteria and can be done in around four hours, meaning there is no need to wait for the bacteria to grow.

"Often, patients have already started to receive antibiotics before the bacteria have had time to grow in the lab," said Morris.

"This means that results from cultures are often negative, whereas PCR doesn't need viable bacteria to detect -- making this a more accurate test," he said.

The Cambridge test runs multiple PCR reactions in parallel, and can simultaneously pick up 52 different pathogens, which often infect the lungs of patients in intensive care.

At the same time, the researchers said, it can also test for antibiotic resistance. — PTI

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