A significant relationship exists between environmental exposures and colonization.
Clostridioides difficile (C diff) is a particularly resilient bacterium that causes thousands of challenging-to-treat infections each year in the United States. The US Centers for Disease Control and Prevention (CDC) estimates that there are roughly 500,000 cases per year in the United States and that 20% of patients with C diff will get it again. Of those recently diagnosed with the bacterium, 1 in 11 over the age of 65 years will die with a health care-associated C diff infection within a month of diagnosis.
C diff challenges health care and infection prevention efforts as most cases often occur during or following antimicrobial treatments. Commonly associated with exposure in a health care setting, the dynamics of C diff transmission make prevention efforts difficult.
To better understand the full spectrum of exposure and transmission, investigators examined the role of exposure to other environmental factors, such as livestock, and C diff infection or colonization at the time of hospital admission. Their findings were published in JAMA Network Open.
The research team employed a retrospective cohort study approach to evaluate over year of data from a hospital in Milwaukee, Wisconsin. Patients underwent C diff screening at hospital admission and main outcomes were those who tested positive within 72 hours of admission (ie those would be considered to have acquired C diff from the community and not health care-associated).
The authors noted that “among registries that include the incidence of C diff infection, only 65% of cases in the United States and 74% of those in Europe were reported to be associated with the health care environment.”
During the study period at Froedtert Memorial Lutheran Hospital, a total of 4617 C diff screening tests were performed. Investigators collected information from patients on sociodemographic and economic variables and also environmental exposures. These exposures were assessed via the patient’s address and the team used geocoding to determine how far they lived from the nearest business location, which was focused on livestock farms, meat processing plants, farm raw materials services, and sewage treatment facilities.
After exclusions, there were a total of 3043 patients, of whom 10.4% (318) were colonized at their first admission to the hospital. The mean age of the cohort was 62 years and roughly 33% of studied patients were over 70 years of age. Of the patients who were colonized on admission, 33.3% had been previously hospitalized within 6 months.
The investigators found that those non-hematology/oncology patients who were recently hospitalized had a 70% higher probability of being colonized, “while increased distance between patient residence and the nearest livestock farm was associated with a significant decrease in the probability of colonization”.
The team assessed the association between environmental and health care exposures by calculating adjusted probabilities for C diff colonization for various scenarios of residential distance to livestock farms and previous hospitalizations.
The authors found that " the independent effect of residential distance to livestock farms was substantial; regardless of health care exposure, the probability of colonization more than doubled for those living 1 mile from a livestock farm compared with those living 50 miles from a livestock farm. Specifically, the probability of colonization increased from 6.5% among those living 50 miles from a livestock farm to 15.7% among those with previous hospitalization and from 4% to 10.6% among those without a recent hospitalization.” Comorbidities played a factor in those patients admitted to a non-hematology/oncology unit, increasing the odds of colonization by more than 4 times.
Overall, this study is immensely important in that it reveals the significant of residential proximity to livestock farms plays a significant role in increasing risk of C diff colonization. For those patients admitted to non-hematology/oncology unit, residential proximity to livestock farms doubled their probability of C diff colonization.
Understanding this relationship is not only critical for working to reduce such exposures, but sheds light on the One Health dynamics of C diff colonization. Further efforts should work to study this complex relationship but also work these findings into hospital admission screening efforts, and even potentially diagnostic.