Findings from a study by researchers from the University of Iowa highlights the potential role of the home environment in Clostridioides difficile transmission.
Using data from a commercial insurance claims database, the researchers found that the incidence of C difficile infection (CDI) among individuals living with a family member who had CDI was more than 12 times greater than the incidence in those without prior family exposure. The incidence rate was even higher in certain groups less likely to have other risk-increasing exposures.
The results of the study appeared Jun 26 in JAMA Open Network.
While the level of absolute CDI risk attributable to the household transmission was extremely low, the authors of the study say the findings may have practical implications for preventing the spread of CDI in households.
CDI can be spread in the community
C. difficile infection (CDI) is a common, typically hospital-acquired infection that is mainly associated with antibiotic use and healthcare settings. While antibiotics create the conditions that allow for C difficile to flourish in the gut and cause infection, spores shed by infected patients (through fecal matter) and can be spread by healthcare workers and are frequently found on *bed rails, in the patient bathrooms, and other parts of the hospital environment.
(*High touch areas can be easily contaminated with Clostridioides difficile (C. difficile, C. diff.) spores) cdf note.
Those spores are often difficult to eliminate because they are resistant to many cleaning agents.
In 2017, according to the most recent data from the Centers for Disease Control and Prevention, there were an estimated 223,900 CDI cases in hospitalized patients.
But not all CDI cases start in hospitals. Some studies have found that CDI can be transmitted outside of healthcare settings, with persistent contamination of the household environment occurring in patients with documented infection. Others have found household pets colonized with the bacterium.
To better understand the potential role of household C difficile transmission, the University of Iowa researchers used a large population-based, commercial insurance claims data set to examine whether family members of CDI patients had a greater risk of acquiring the infection. Limiting the analysis to households with two or more family member enrolled in the same insurance plan for an entire month, they grouped individuals into four categories based on CDI status and family exposure to CDI: (1) CDI and prior family exposure, (2) no CDI and prior family exposure, (3) CDI and no family exposure, and (4) no CDI and no family exposure.
The primary outcome of the case-control study was the incidence of CDI in a given monthly enrollment stratum. Aside from exposure to CDI diagnosed in a family member, other CDI exposure risks were considered, including prior hospitalization, age, and antibiotic use. The researchers also conducted a separate analysis for CDI diagnosed in hospital or outpatient settings.
Higher risk from family exposure
Analysis of data covering 2001 through 2017 found that 224,818 CDI cases, representing 194,424 enrollees, occurred in families with at least two enrollees. Of these, 1,074 CDI cases (0.48%) occurred following a diagnosis in a separate family member, representing possible transmission. In general, the index cases of CDI tended to occur in older enrollees (ages 45 to 64 years), while the CDI cases that represented potential transmission events occurred in children.
A comparison of the incidence rate ratio (IRR) between individuals with and without family exposure showed that prior family exposure was significantly associated with an increased incidence of CDI (IRR, 12.47; 95% confidence interval [CI], 8.86 to 16.97) even after controlling for other risk factors. This was the second-highest IRR behind hospital exposure (IRR, 16.18; 95% CI, 15.31 to 17.10).
Increased CDI incidence was also associated with age (IRR, 9.90; 95% CI, 8.93 to 10.98 for people over age 65 compared with those aged 0 to 17) and antibiotic use (IRR, 7.78; 95% CI, 7.33 to 8.25 for people on high-CDI-risk antibiotics compared with no antibiotics).
When the researchers looked at subgroups of CDI cases less likely to be attributed to hospital exposure, they found that the IRR associated with family exposure was even higher—16.00 (95% CI, 11.72 to 21.22) for community-onset CDI and 21.74 (95% CI, 15.12 to 30.01) for community-onset CDI without prior hospitalization.
“For individuals with family exposure, the risk for being diagnosed with CDI remained consistent after controlling for CDI risk factors and different model specifications,” the authors wrote. “Together, these results suggest that individuals with family exposure may be at greater risk for acquiring CDI than those without exposure and highlight the importance of the shared environment in the transmission and acquisition of C difficile.”
The authors note that because they were not able to conduct whole-genome sequencing, they cannot confirm whether CDI cases within families represent identical strains. They also said the study is limited by the reliance on insurance claims data, which do not provide all the details necessary to determine attributable risk.
Despite the low absolute risk of acquiring CDI from a family member, the authors suggested that cleaning shared bathrooms with effective cleaning agents could be a practical way to minimize transmission risk.
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