Asymptomatic C diff Associated With Pathogen Reservoir, Affecting Carriers, Patients, Employees in ICU

A ceiling mounted hospital directional sign highlighting the way towards the intensive care unit – 3D render
Genomically-confirmed assessments of the risk for CDI found that asymptomatic carriers serve as viral reservoirs in clinical settings.

Asymptomatic carriers of Clostridioides difficile infections (CDI) are active reservoirs in nosocomial environments, according to data published in Clinical Infectious Diseases.

For the first time, genomically-confirmed assessments of the risk for CDI from asymptomatic carriage of toxin-encoding strains were conducted and found relative risk for CDI with asymptomatic carriage of a toxin-encoding strain was 9.32 (95% CI, 3.25-26.7).      

CDIs are among the most prevalent infections in hospital settings, especially in the intensive care unit (ICU). However, the risk of developing active CDI from asymptomatic carriage of C diff is not well understood.  Investigators therefore undertook ICU surveillance for C diff to examine the risks associated with asymptomatic C diff carriage.

A genomic screening pilot collected 2432 vancomycin-resistant Enterococci (VRE) swabs from 1897 patients in the ICU. In total, 172 C diff isolates were identified in 143 patients. Swabs and stool samples were genome sequenced, while spatial-temporal data from hospital records were used to assess genomically-identified clusters for potential transmission events.

In infected patients and asymptomatic carriers, genomic analyses identified a diverse set of strains. Results revealed that 7.4% of patients in the ICU were asymptomatic carriers of C diff, and 69% of isolates carried an intact toxin locus; 96% of C diff isolates were toxin-encoding. Rates of CDI in asymptomatic carriers of toxin-encoding strains were 5.3% compared with 0.57% in non-carriers. The relative risk for CDI with asymptomatic carriage of a toxin-encoding strain was 9.32 (95% CI, 3.25-26.7). The occurrence of asymptomatic transmission events was supported by genomic identification of clonal clusters and spatial-temporal overlaps in 13 of 28 cases.

“Asymptomatic carriers of C diff provide a significant and hidden pathogen reservoir that can have adverse effects for carriers, other patients, and healthcare workers,” the researchers wrote. Furthermore, their work demonstrates constructive use of existing hospital surveillance programs and nationally available genomic tools and resources to undertake ICU surveillance for CDI. “Leveraging this model, institutions can make informed decisions regarding the utility of screening to reduce CDI incidence,” they concluded.

Disclosure: One study author declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.


Worley J, Delaney ML, Cummins CK, DuBois A, Klompas M, Bry L. Genomic determination of relative risks for Clostridioides difficile infection from asymptomatic carriage in ICU patients. [published online July 17, 2020]. Clin Infect Dis. doi: 10.1093/cid/ciaa894