Neighborhood Antibiotic Use Linked to Community-Associated C. difficile in Older Adults

Neighborhoods with higher antibiotic utilization had higher rates of community-associated Clostridioides difficile infection (CA-CDI) among older adults, according to an ecological study of 1,520 neighborhoods in Ontario, Canada, published in Clinical Infectious Diseases.

The investigators noted that hospital-associated C. difficile infection (CDI)  incidence has declined in Canada and the US while CA-CDI incidence has remained high. To their knowledge, no previous study had examined neighborhood-level antibiotic utilization and its association with CDI incidence.

The study included Ontario residents aged 66 years or older without a recent acute care or emergency department exposure from 2017 to 2023 and identified 19,757 CA-CDI cases. Antibiotic utilization varied substantially across neighborhoods, with a median of 21.1 days of therapy per 1,000 person-days (interquartile range, 16.7-25.6). After adjustment for 8 demographic and healthcare covariates, each increase of 10 days of therapy per 1,000 person-days was associated with a higher CA-CDI rate (rate ratio, 1.13; 95% CI, 1.09-1.18).

Associations strengthened with the CDI risk of the antibiotic class. Per 10-point increase in days of therapy per 1,000 person-days , adjusted rate ratios were 1.08 for low-risk agents; 1.26 for moderate-risk agents, including amoxicillin-clavulanate, fluoroquinolones, and first- and second-generation cephalosporins; and 1.73 for high-risk agents, clindamycin and third- and fourth-generation cephalosporins. The high-risk estimate was imprecise (95% CI, 1.13-2.66), and these agents were relatively infrequently prescribed. The analysis did not establish a clear association for no-risk agents. The proportion of residents hospitalized in the prior year was the strongest predictor of neighborhood CDI rates, whereas the proportion living in long-term care was not associated.

The authors suggested that tracking and reducing neighborhood-level antibiotic exposure may be a valuable addition to antimicrobial stewardship. They noted that the ecological design could not verify individual antibiotic exposure before CDI, that residual confounding is possible, that the population was limited to older adults, and that some hospital-acquired cases were likely classified as community-associated.

Source: Hakin K, Daneman N, Hernandez A, et al. Association between neighbourhood-level antibiotic utilization and the rate of community-associated C. difficile (CA-CDI) infection: an ecological study. Clin Infect Dis. Published online October 19, 2026. doi:10.1093/cid/ciag661