A new study by researchers at the University of Utah suggests one of the most common healthcare-associated infections (HAIs) spreads more widely in intensive care units (ICUs) than previously understood.
The findings, published last week in JAMA Network Open, are based on genomic analysis of Clostridium difficile isolates collected from two ICUs in Utah in 2018. The researchers were aiming to quantify rates of C difficile spread across the two ICUs and describe transmission dynamics. C difficile causes severe diarrhea and is a leading cause of HAIs around the world, accounting for 223,000 hospitalizations and 12,800 deaths in the United States each year.
While most genomic studies of C difficile transmission in hospitals analyze patient samples, this study also included sampling of healthcare provider (HCP) hands and the hospital environment to understand how the pathogen moves between patients and hospital surfaces. What the researchers found was that nearly 8% of admitted patients had C difficile that was genetically linked to another patients, and that movement of the pathogen was more than threefold higher than if they had relied on patient sampling alone.
"There's a lot going on under the hood that we're just not seeing," senior study author Michael Rubin, MD, PhD, an epidemiologist and infectious disease specialist at the University of Utah, said in a university press release.
Expanded sampling captures more C diff transmission
During the 13-week study, researchers collected daily samples from three patient body sites, three surfaces in patient rooms (patient touch surfaces, HCP touch surfaces, and toilet surfaces), and hands or gloves of HCPs who cared for the patient. They then conducted whole genome sequencing (WGS) on both toxigenic and nontoxigenic C difficile isolates to identify transmission clusters (defined as isolates with two or fewer single nucleotide variants between them). Nontoxigenic C difficile strains are usually not associated with infection and not included in most surveillance studies.
A total of 7,000 samples were collected across 278 unique ICU admissions over the course of the study, with 177 patients consenting to body-site sampling. From those samples, researchers recovered 178 C difficile isolates—46 from patient body sites, 87 from patient rooms, 1 from a shared environmental surface, and 44 from HCP hands.
There's a lot going on under the hood that we're just not seeing.
WGS analysis identified seven transmission clusters involving 22 (7.7%) of 287 occupant stays. Of the clusters, two included isolates from two distinct occupants' body sites, suggesting patient-to-patient transmission, while two others included environmental or HCP hand isolates and patient isolates, which means a patient acquired from or shed the pathogen into the environment or the hands of an HCP caring for another occupant. The remaining 3 included isolates from environmental surfaces from multiple occupant stays. Only two of the 22 clustered occupant stays involved sequential occupants of the same room.
"Importantly, 5 of these transmission clusters (71.4%) would have been missed without the expanded sampling of environmental surfaces and HCP hands because they did not include patient body site isolates from multiple occupant stays," the study authors wrote.
The authors note that most of the C difficile isolates were nontoxigenic and that only two patients, both in the same hospitals, were identified as having C difficile infection. But the fact that so many of the transmission clusters included isolates from environmental surfaces and HCP hands suggests C difficile transmission in ICUs has been underestimated in previous studies, and it could indicate lapses in infection prevention and control that could allow for the spread of toxigenic C difficile.
"What I'm hoping we get from this paper is that health care providers put a greater emphasis on infection prevention measures and adhere to them as much as they possibly can," Rubin said.
