784 - A Novel Method to Assess Virulence of Clostridioides difficile: Focus on C. difficile Ribotype 106

Background: Clostridioides difficile ribotype (RT) 106 has emerged as one of the most commonly isolated strains in the USA and worldwide.  However, studies investigating clinical outcomes associated with this strain are lacking. The purpose of this study was to compare disease severity, clinical cure, and recurrence rates associated with CDI caused by RT106 vs two other comparator strains.

Methods: This multicenter study (20 hospitals) assessed hospitalized patients infected with C. difficile RT106 compared to patients infected with a known hypervirulent strain (RT027) and a strain associated with less virulence (RT014-020). Electronic medical records were reviewed by investigators blinded to RT. Disease severity was calculated using the 2017 IDSA/SHEA guidelines, initial clinical cure was defined as resolution of symptoms by day 6 of treatment, and recurrence assessed 90-days after the initial positive toxin test.  All isolates were ribotyped using PCR fluorescent ribotyping.

Results: A total of 380 patients with CDI aged 66 ± 17 years (Female: 59.5%; White: 70.5%) infected with RT 106 (115/380; 30.3%), RT027 (116/380; 30.5%), and RT014-020 (149/380; 39.2%) were included. Approximately half of the patients had severe CDI (47.6%).  Disease severity was highest for RT027 (59.3%) followed by RT014-020 (45%), and RT106 (41.2%). Clinical cure rates were lowest for RT027 (74.8%) followed by RT106 (77.8%), and RT014-020 (85.5%).  90-day recurrence rates were highest for RT027 (20.7%) followed by RT106 (13.3%), and RT014-020 (8.7%). Compared to RT014-020, virulence increased with RT106 (OR:1.10; 95% CI: 0.67-1.8) and RT027 (OR: 2.0: 95% CI: 1.2-3.5) was noted.

Conclusion: Our novel analysis method established RT106 as a moderately virulent C. difficile strain vs. comparator ribotypes. This study presents a novel method for comparing clinical outcomes for emerging ribotypes.