Increased Community-Associated Clostridioides difficile Infections in Quebec, Canada, 2008–2015

Veronica Zanichelli; Christophe Garenc; Jasmin Villeneuve; Danielle Moisan; Charles Frenette; Vivian Loo; Yves Longtin


Emerging Infectious Diseases. 2020;26(6):1291-1294. 

In This Article


Although the incidence of HA-CDI has been decreasing in Canada since 2009,[12] our study suggests possible emergence of CA-CDI in the province of Quebec because the number, incidence, and proportion of reported cases have been steadily increasing since 2008. This increased incidence contrasts markedly with the overall decreasing trend of HA-CDI incidence after April 2011.

Emergence of CA-CDI has been reported in other countries.[4–6,13] A 2008–2013 study in Finland reported an increase in probable CA-CDI cases at an annual rate of 4.3% compared with a concomitant decrease in HA-CDI cases at an annual rate of 8.1%.[4] In the United Kingdom, an analysis of hospital administrative data detected an increase in the proportion of CDI cases that were community acquired, from 7% in 1998 to 13% in 2010, while the overall incidence of CDI cases fell to less than half of peak rate.[13] The US Veterans Healthcare Administration reported similar findings of an increased proportion of CDI cases that were community-associated (from 8.3% in 2003 to 26.7% in 2014).[5] Electronic patient records analysis in Hong Kong identified a 3-fold increase in the incidence of CA-CDI cases, from 0.86/100,000 population in 2006 to 2.96/100,000 population in 2014.[6] These reports suggest that CA-CDI may be increasing worldwide; however, because the studies relied on retrospective extraction of data that were not specifically collected for CDI surveillance, they may be susceptible to misclassification and reporting biases.[14]

The factors underlying this apparent increase in CA-CDI incidence are unclear. However, we hypothesize that this rise may result from any combination of the following: increased disease severity, leading to a greater proportion of case-patients being hospitalized; increased use of antimicrobial drugs or proton-pump inhibitors in the community; emergence of community-specific novel virulent C. difficile strains; and heightened awareness by physicians to consider the diagnosis of CDI.

Our study has many strengths. We used prospectively collected data from a well-established surveillance program enrolling virtually all persons admitted to acute-care hospitals in the province, thereby limiting selection bias, and we used standardized case definitions to avoid misclassification issues. However, our study also has several limitations. Only persons hospitalized with CA-CDI were reported to the surveillance program; therefore, milder cases were not captured. Thus, the actual incidence of CA-CDI may be underestimated. Because no clinical data regarding patients in whom CDI develops were collected, we cannot characterize patients or investigate potential changes in the affected population. We could not investigate the effect of diagnostic assay modifications on the observed change in trend because this information was not collected. Nucleic acid amplification tests are more sensitive than enzyme immunoassays for detecting toxigenic C. difficile; thus, increased use of these tests could lead to increased CA-CDI incidence rates. However, use of a more sensitive assay would be expected to affect CA-CDI and HA-CDI incidence similarly, whereas these trends are clearly divergent.

In conclusion, CA-CDI incidence in the province of Quebec increased significantly during 2008–2015 despite an overall decrease in HA-CDI incidence. This divergence in trends suggests a need to devote more attention to CA-CDI.