Deadly hospital infection may have surprising origin

Deadly Clostridioides difficile infections may not result from transmission, but from within the infected patient themselves, a new study shows.

Hospital staff spend a significant amount of time working to protect patients from acquiring infections while they are being cared for in the hospital. They employ various methods from hand hygiene to isolation rooms to rigorous environmental sanitation.

Despite these efforts, hospital-onset infections still occur—the most common of which is caused by the bacterium C. diff, the culprit of almost half a million infections in the United States each year.

For the study, published in Nature Medicine, researchers led by Evan Snitkin, and Vincent Young, both members of the microbiology and immunology and internal medicine/infectious diseases department at the University of Michigan Medical School and Mary Hayden, of Rush University Medical Center, leveraged ongoing epidemiological studies focused on hospital-acquired infections that enabled them to analyze daily fecal 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 Snitkin’s lab, analyzed the over 1,100 patients in the study, and found that a little over 9% were colonized with C. diff. Using whole genome sequencing of 425 C. difficile strains isolated from nearly 4,000 fecal specimens, she compared the strains to each other to analyze spread.

“By systematically culturing every patient, we thought we could understand how transmission was happening. The surprise was 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 colonized 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 diarrhea and the other complications resulting from infection,” Snitkin says.

This doesn’t mean hospital infection prevention measures are not needed, Hayden says. In fact, the measures in place in the Rush ICU at the time of the study—high rates of compliance with hand hygiene among health care 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 colonized and try to prevent infection in them.

“They are sort of all around us,” says 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 sanitizer.”

However, only about 5% of the population outside of a health care 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,” says Young.

The team next hopes to build on work investigating the use of AI models to predict patients at risk of C. diff infection to identify patients who are likely to be colonized and who could benefit from more focused intervention.

“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 optimize the use of antibiotics and identify other triggers that lead patients harboring C. diff and other health care pathogens to develop serious infections,” Snitkin says.

Source: University of Michigan