Clostridium bacteria, C. diff, illustration

A new study from researchers at the University of Michigan has provided surprising findings indicating that hospital-onset Clostridioides difficile, or C. diff, infections may come from characteristics associated with the patients themselves and not via hospital transmission. The findings, reported today in Nature Medicine, could help support additional steps needed to help prevent infections in patients.

Hospitals typically expend significant time and effort to protect patients from developing infections while being cared for in the hospital including hand hygiene, environmental sanitation, and isolating infected patients. Yet despite all these established practices, infections that begin in the hospital remain a stubborn problem.

The nine-month study was led by researchers Evan Snitkin, PhD, and Vincent Young, MD, PhD, who are members of the departments of microbiology & immunology and internal medicine/infectious diseases at the University of Michigan Medical School and their colleague Mary Hayden, MD, at Rush University Medical Center. Their research leveraged ongoing epidemiological studies of hospital-acquired infections (HAIs) that provided them with the opportunity to analyze over the course of nine months fecal samples obtained from every patient in the Rush University Medical Center.

The study analyzed more than 1,100 patients and found that slightly more than 9% of the patients were colonized with C. diff. Snitkin Lab postdoc Arianna Miles-Jay, PhD, conducted whole-genome sequencing of 425 C. diff strains isolated from roughly 4,000 fecal samples in order to compare the strains to each other as a method to analyze their spread.

“By systematically culturing every patient, we thought we could understand how transmission was happening,” Miles-Jay said. “The surprise was that, based on the genomics, there was very little transmission.”

In other words, the analysis showed that there was little evidence showing that patients were carrying the same strains of C. diff, which would imply they had acquired the infection while in the hospital. In total, the research team found only six in-hospital transmissions were supported by their data and showed that instead, people who were already colonized with C. diff were at greater risk of moving to an active 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,” said Snitkin.

Hayden noted that these new findings, while eye-opening and counter to previous thinking, do not mean hospitals’ infection prevention protocols are not needed. The researchers noted that 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. However, the new data suggests that more steps may be needed to identify the patients who are already colonized and develop methods that prevent infections from developing.

While acknowledging the hearty nature of C. diff, the investigators noted that only about 5% of people outside the healthcare setting have C. diff in the gut and that it typically causes no issues. However, understanding the risks of these patients once they have entered the hospital setting is the next step to preventing infection. The researchers say their next step is to develop AI models that can help them identify patients who are likely to be colonized and develop interventions that could benefit them.

“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.

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