A global study of C. difficile isolates worldwide found a very high prevalence of the bacteria on shoe soles.
Clostridioides difficile is the leading cause of healthcare-associated infections, but it is often only studied in healthcare settings. A study by the University of Houston and presented virtually at IDWeek explored environmental reservoirs that may assist in C. difficile transmission, examining the strain type and prevalence.
From 2014-2017, investigators collected environmental swabs from healthcare settings, public areas, and shoe soles. To be considered positive for C. difficile, samples had to exhibit growth on CCFA plates and PCR test positive for toxin genes and fluorescent PCR ribotyping (RT). Investigators compared rate of C. difficile positivity and associated RT distribution between settings. They specifically examined shoe soles for their potential role in environmental transmission.
Investigators gathered a total of 11986 unique samples, obtained primarily from the US (n=11002; 92%), with a minority from 11 other countries including Taiwan (n=22) and India (n=187). Samples were from outdoor environments (n=2992), private residences (n=2772), shoe soles (n=1420), public buildings (n=1104), and acute care settings (n=3698).
The C. difficile positivity rate was 26%, similar between sampling sites in and outside of the US. The most prevalent RTs were F014-020 (16.4%), F106 (14.9%), and FP310 (11%).
In the US, private residences (26.2%) and outdoor environments (24.1%) had significantly higher positivity rates than public buildings (17.2%). However, in a Texas-based sub-analysis (n=8571), positivity rates were highest in outdoor spaces (27%) and slightly lower in private residences and healthcare buildings (both 24%).
At 45%, shoe soles had the highest positivity rate, with similar RT distribution between shoe soles and environmental samples.
The investigators concluded by recommending community stewardship efforts to reduce the risk of C. difficile infection in healthcare and non-healthcare sites. Shoe sole sampling, which produced shocking results, may be a useful method of testing for emerging epidemic strains.