A simple DNA test has been developed that can identify secondary infections in Covid-19 patients who have double the risk of developing pneumonia while on ventilation than non-Covid-19 patients.

Ventilator-associated pneumonia are often caused by antibiotic-resistant bacteria, and are hard to diagnose and need targeted treatment.

The test, developed at Addenbrooke's hospital in collaboration with Public Health England, 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.

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.

The results have been published in Critical Care and show how the test can run multiple polymerase chain reactions (PCR) in parallel. It can also simultaneously pick up 52 different pathogens, which often infect the lungs of patients in intensive care. At the same time, it can also test for antibiotic resistance.

Covid-19 patients are at risk of developing secondary pneumonia

Dr Andrew Conway Morris from Cambridge's Department of Medicine and an intensive care consultant said: "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.

"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."

Covid-19 patients are thought to be at increased risk of infection for several reasons. Due to the amount of lung damage, these severe Covid-19 cases tend to spend more time on a ventilator than patients without Covid-19. In addition, 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.

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

This is one of the first times that this technology has been used in routine clinical practice and has now been approved by the hospital. The researchers anticipate that similar approaches would benefit patients if used more broadly.