Two Distinct Patterns of Clostridium difficile Diversity Across Europe Indicating Contrasting Routes of Spread.

Background: Rates of Clostridium difficile infection vary widely across Europe, as do prevalent ribotypes. The extent of Europe-wide diversity within each ribotype, however, is unknown.

Methods: Inpatient diarrheal fecal samples submitted on a single day in summer and winter (2012-2013) to laboratories in 482 European hospitals were cultured for C. difficile, and isolates the 10 most prevalent ribotypes were whole-genome sequenced. Within each ribotype, country-based sequence clustering was assessed using the ratio of the median number of single-nucleotide polymorphisms between isolates within versus across different countries, using permutation tests. Time-scaled Bayesian phylogenies were used to reconstruct the historical location of each lineage.

Results: Sequenced isolates (n = 624) were from 19 countries. Five ribotypes had within-country clustering: ribotype 356, only in Italy; ribotype 018, predominantly in Italy; ribotype 176, with distinct Czech and German clades; ribotype 001/072, including distinct German, Slovakian, and Spanish clades; and ribotype 027, with multiple predominantly country-specific clades including in Hungary, Italy, Germany, Romania, and Poland. By contrast, we found no within-country clustering for ribotypes 078, 015, 002, 014, and 020, consistent with a Europe-wide distribution. Fluoroquinolone resistance was significantly more common in within-country clustered ribotypes (P = .009). Fluoroquinolone-resistant isolates were also more tightly clustered geographically with a median (interquartile range) of 43 (0-213) miles between each isolate and the most closely genetically related isolate, versus 421 (204-680) miles in nonresistant pairs (P < .001).

Conclusions: Two distinct patterns of C. difficile ribotype spread were observed, consistent with either predominantly healthcare-associated acquisition or Europe-wide dissemination via other routes/sources, for example, the food chain.