Methods: We performed a retrospective cohort study of 56 patients who experienced a recurrent episode of C. difficile infection more than 8 weeks after the index episode (classified as new infection). Multiple colony typing (five colonies per sample) of toxigenic C. difficile isolates retrieved from the index and second episode was performed by multi-locus sequencing technique (MLST) to characterize role of mixed infections in recurrent CDI .
Results: 31 (55%) of the 56 patients tested had no discordance in MLST strain type between the index and relapse episodes. Multiple colony typing could be successfully performed in 23/25 remaining cases. 18 patients (32%) had discordant MLST strain types between episodes, but with unique MLST strain types across the five colonies that were tested, suggesting new infection rather than relapse. Mixed infection with 2 MLST strains during the initial episode was detected in 5 patients; 4 (7%) among these had a subsequent relapse due to one of original infecting strains. 1 patient (1.79%) had new infection due to a strain distinct from all the original infecting strains.
Conclusion: Mixed infection was seen in 9% of all CDI episodes in our cohort. Relapse attributed to mixed infection was suspected to occur in 7% of cases of recurrent CDI that occur more than 8 weeks after the index episode.
N. E. Babady, None
M. Kamboj, None
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