Despite strenuous control efforts, hospital-acquired infections still occur – the most common of which is caused by the bacterium Clostridioides difficile, which creates lingering spores and resists alcohol-based hand sanitisers. Surprising findings from a new study in Nature Medicine suggest that the burden of C. diff infection may be less a matter of hospital transmission and more a result of characteristics associated with the patients themselves.
The study team, led by Evan Snitkin, PhD; Vincent Young, MD, PhD; and Mary Hayden, MD, leveraged ongoing epidemiological studies focused on hospital-acquired infections that enabled them to analyse daily faecal samples from every patient within the intensive care unit at Rush University Medical Center over a nine-month period.
Arianna Miles-Jay, a postdoctoral fellow in Dr Snitkin’s lab, analysed 1141 eligible patients, and found that a little over 9% were colonised with C. diff. Using whole genome sequencing at U-M of 425 C. difficile strains isolated from nearly 4000 faecal specimens, she compared the strains to each other to analyse spread. But she found that, based on the genomics, there was very little transmission.
Essentially, there was very little evidence that the strains of C. diff from one patient to the next were the same, which would imply in-hospital acquisition. In fact, there were only six genomically supported transmissions over the study period. Instead, people who were already colonised were at greater risk of transitioning to infection.
“Something happened to these patients that we still don’t understand to trigger the transition from C. diff hanging out in the gut to the organism causing diarrhoea and the other complications resulting from infection,” said Snitkin.
Hayden notes this doesn’t mean hospital infection prevention measures are not needed. In fact, the measures in place in the Rush ICU at the time of the study – high rates of compliance with hand hygiene among healthcare personnel, routine environmental disinfection with an agent active against C. diff, and single patient rooms were likely responsible for the low transmission rate. The current study highlights, though that more steps are needed to identify patients who are colonised and try to prevent infection in them.
Where did the C. diff come from? “They are sort of all around us,” said Young. “C. diff creates spores, which are quite resistant to environmental stresses including exposure to oxygen and dehydration…for example, they are impervious to alcohol-based hand sanitiser.”
However, only about 5% of the population outside of a healthcare setting has C. diff in their gut – where it typically causes no issues.
“We need to figure out ways to prevent patients from developing an infection when we give them tube feedings, antibiotics, proton pump inhibitors – all things which predispose people to getting an actual infection with C. diff that causes damage to the intestines or worse,” said Young.
The team next hopes to build on work on AI prediction for patients at risk of C. diff infection to identify patients more likely to be colonised and who could benefit from more focused intervention.
Said Snitkin, “A lot of resources are put into gaining further improvements in preventing the spread of infections, when there is increasing support to redirect some of these resources to optimise the use of antibiotics and identify other triggers that lead patients harbouring C. diff and other healthcare pathogens to develop serious infections.”
