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• Posted September 20, 2023

Patient-to-Patient Transmission Not to Blame for Most C. Difficile Infections in Hospitals

A deadly infection associated with hospitalization may not be the fault of the hospital, but may instead stem from the patients themselves, a new study suggests.

Infection caused by the bacterium Clostridioides difficile, or C. diff, is still common in hospitals, despite extensive infection control procedures. The new research may help explain why that's so.

Among more than 1,100 patients at a Chicago hospital, a little over 9% were "colonized" with C. diff. Analysis of nearly 4,000 fecal specimens showed very little evidence that the strains of C. diff from one patient to the next were the same, which would imply in-hospital acquisition.

But only six possible patient-to-patient transmissions were found. Instead, people who already carried the bug without symptoms were at greater risk of transitioning to symptomatic infection, the researchers said.

In fact, patients who already had C. diff hanging out in their guts were at 24-times greater risk for developing a health care-onset C. difficile infection than non-carriers.

"Our findings suggest that measures in place in the 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 effective in preventing C. diff transmission," said lead researcher Evan Snitkin, an associate professor in the Department of Microbiology and Immunology at the University of Michigan Medical School.

"This indicates that to make further progress in protecting patients from developing C. diff infections will require improving our understanding of the triggers that lead patients asymptomatically carrying C. diff to transition to having infections," Snitkin said.

According to the U.S. Centers for Disease Control and Prevention, nearly half a million C. diff infections occur in the United States each year. Between 13,000 and 16,000 people die from the bacterium, which causes watery diarrhea and inflammation of the colon. Many of these infections and deaths have been blamed on transmission between hospitalized patients.

However, past work has consistently shown that the majority of C. diff infections in hospitals could not be explained by transmission from other patients with infections, Snitkin said. His team came to the same conclusion after analyzing daily fecal samples from every patient in the intensive care unit at Rush University Medical Center in Chicago over nine months.

These findings don't mean hospital infection prevention measures are not needed. In fact, they were likely responsible for the low transmission rate, Snitkin said. More steps, however, are needed to identify patients who carry C. diff and try to prevent infection, he said.

Hannah Newman is senior director of infection prevention at Lenox Hill Hospital in New York City.

"When a person is exhibiting symptoms, it is easy to identify and begin the necessary infection prevention strategies to prevent spread," said Newman, who had no part in the study. However, "sometimes a patient can have C. diff in their gut but not experience symptoms. We call this colonization."

What exactly triggers active infection in people who carry C. diff isn't clear but antibiotic use is suspected to play a role.

"These findings suggest that while we should continue our current infection prevention strategies, attention should also be given to identifying the individuals who are asymptomatic carriers and finding ways to reduce their risk of developing an infection, like carefully optimizing antibiotic usage and recognizing other risk factors," Newman said.

Snitkin said antibiotic usage isn't the only culprit. "There is support for antibiotic disruption of the microbiota being one type of trigger event, but there is certainly more to it than that, as not every patient who carries C. diff and receives antibiotics will develop an infection," he said.

Older patients and those who have been hospitalized before are at the greatest risk of carrying C. diff, said Donna Armellino, senior vice president of infection prevention at Northwell Health in Manhasset, N.Y.

"Many patients are already colonized," said Armellino, who was not involved with the study. "A lot of their normal flora in their GI tract can be altered either through surgery or antibiotics or some other mechanism, and then symptoms occur and that's when they are treated with antibiotics."

According to background notes in the study, only about 5% of the population outside of a health care setting has C. diff in their gut -- where it typically causes no issues.

Armellino said the hospital can control the environment but not whether a patient is carrying C. diff. And it's not usual practice to give patients antibiotics to prevent a C. diff infection before it occurs, although "this definitely needs to be studied."

She also suggested that perhaps the patient-to-patient transmission rate was so low in this research because the ICU they studied had private rooms, noting patients in many hospitals share bathrooms and are in close proximity.

The report was published Sept. 18 in the journal Nature Medicine.

More information

For more on C. diff, see the U.S. Centers for Disease Control and Prevention.

SOURCES: Evan Snitkin, PhD, associate professor, microbiology and Immunology, University of Michigan Medical School, Ann Arbor; Hannah Newman, MPH, senior director, infection prevention, Lenox Hill Hospital, New York City; Donna Armellino, RN, senior vice president, Infection Prevention, Northwell Health, Manhasset, N.Y.; Nature Medicine, Sept. 18, 2023