C. difficile may not originate from external transmission but from the infected patient itself. Hospital staff work hard to protect patients from infection during their stay. They work to prevent infection through practices ranging from hand hygiene to the use of isolation rooms and strict cleaning procedures. However, even with these measures in place, nosocomial infections still occur, the most common of which is caused by Clostridium difficile (C.diff), which is responsible for nearly 500,000 infections in the United States each year.
Surprising findings from a new study in Nature Medicine suggest that the burden of Clostridium difficile infection may not be a problem of nosocomial transmission but rather the result of characteristics associated with the patients themselves.
The research team is led by Dr. Evan Snitkin. Vincent Young, MD, of the Departments of Microbiology and Immunology and Internal Medicine/Infectious Diseases at the University of Michigan Medical School, and Mary Hayden, MD, of Rush University Medical Center, used ongoing epidemiological research focused on hospital-acquired infections to allow them to analyze daily stool samples from every patient in Rush University Medical Center's intensive care unit over a nine-month period.
Arianna Miles-Jay, a postdoctoral researcher in Dr. Snitkin's lab, analyzed more than 1,100 patients in the study and found that just over 9 percent were colonized with C. difficile. Using whole-genome sequencing of 425 C. difficile strains isolated from nearly 4,000 stool samples at the University of Michigan, she compared the strains to each other to analyze transmission.
"By systematically culturing samples from each patient, we thought we could understand how transmission occurs. Surprisingly, based on the genomics, the transmission rate was very low."
Essentially, there is little evidence that strains of C. difficile are the same from one patient to another, meaning acquired within a hospital setting. In fact, there were only six genome-supported transmissions during the study period. Conversely, people who are already colonized are at greater risk of becoming infected.
"Something is happening in these patients that we still don't understand that causes C. difficile in the gut to transform into microorganisms that cause diarrhea and other infectious complications," Snitkin said.
That doesn't mean no hospital infection prevention measures are needed, Hayden noted. In fact, the measures taken in the Rush ICU at the time of the study - high compliance with hand hygiene by medical staff, routine environmental disinfection with anti-C. The current study highlights that although more needs to be done to identify colonized patients and attempt to prevent their infection.
Where does C. difficile come from? "They are all around us, and C. difficile produces spores that are highly resistant to environmental stressors, including exposure to oxygen and dehydration... For example, they are not affected by alcohol-based hand sanitizer."
However, only about 5% of the non-healthcare population has C. difficile in their guts - and it usually doesn't cause any problems.
"We need to figure out ways to prevent patients from developing infections when we give them tube feedings, antibiotics, proton pump inhibitors — all of which can make people susceptible to C. difficile infection, which can lead to intestinal damage or worse," Yang said.
Next the team hopes to build on its work investigating the use of artificial intelligence. Models predict patients at risk for C. difficile infection to identify patients who are likely to be colonized and who could benefit from more targeted intervention.
"Significant resources are being devoted to further improving prevention of the spread of infection, and there is growing support for directing some of these resources to optimizing antibiotic use and identifying other triggers that lead patients to harbor C. difficile and other bacteria," Snitkin said.