Could save many lives from common COVID complication
University
of Cambridge
For
patients with the most severe forms of COVID-19, mechanical ventilation is
often the only way to keep them alive, as doctors use anti-inflammatory
therapies to treat their inflamed lungs. 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,
a team of scientists and doctors at the University of Cambridge and Cambridge
University Hospitals NHS Foundation Trust, led by Professor Gordon Dougan, Dr
Vilas Navapurkar and Dr Andrew Conway Morris, have developed a simple DNA test
to quickly identify these infections and target antibiotic treatment as needed.
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 are
reported in the journal Critical Care.
Patients who need mechanical ventilation are at significant risk of developing secondary pneumonia while they are in intensive care. These infections are often caused by antibiotic-resistant bacteria, and are hard to diagnose and need targeted treatment.
"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 co-author Dr Andrew Conway Morris from Cambridge's Department of Medicine
and an intensive care consultant. "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.
The
test 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
antobiotics 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."
The
test -- which was developed with Dr Martin Curran, a specialist in PCR diagnostics
from Public Health England's Cambridge laboratory -- 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,
it can also test for antibiotic resistance.
"We
found that although patients with COVID-19 were more likely to develop
secondary pneumonia, the bacteria that caused these infections were similar to
those in ICU patients without COVID-19," said lead author Mailis Maes,
also from the Department of Medicine. "This means that standard antibiotic
protocols can be applied to COVID-19 patients."
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.
This
study was funded by the National Institute for Health Research Cambridge
Biomedical Research Centre.
