1669. A US Based National Surveillance Study for the Susceptibility and Epidemiology of Clostridioides difficile Associated Diarrheal Isolates with Special Reference to Ridinilazole: 2020-2021
Authors: McDermott Laura A , Thorpe Cheleste M , Goldstein Ellie , Schuetz Audrey , Johnson Stuart , Gerding Dale N , Carroll Karen C , Garey Kevin W , Lancaster Chris , Walk Seth , Duperchy Esther , Snydman David R , Gluck Linda , Bourdas Dimitrios 
Published: December 2022

Abstract

Background
We have previously reported on a US based national surveillance study from 6 geographically dispersed medical centers for the susceptibility and epidemiology of C. difficile isolates. This current survey was conducted with isolates collected in 2020-21 with specific attention to the susceptibility to ridinilazole as well as nine comparators.
A summary of the susceptibilities of 300 isolates of C. difficile tested against 10 antimicrobial agents

Methods
in 2020-21 C. difficile isolates or stools from patients with C. difficile toxin positive antibiotic associated diarrhea were collected in 6 US medical centers and referred to a central lab. After confirmation of 300 isolates antibiotic susceptibilities were determined by agar dilution method (CLSI M11-A9) against 10 agents listed in Table below. Ribotyping was performed by PCR capillary gel electrophoresis on all isolates.

Results
A summary of the susceptibilities of the 300 isolates against 10 antimicrobial agents are shown in the Table. The most common ribotype was 014-020 (14.4% compared to 11.8% in 2016), followed by 106 (10%, compared to 15% in 2016), 027 (10% compared to 13.1% in 2016), 002 (8% compared to 8.5% in 2016, 078-126 (4.3% compared to 1.3% in 2016). Ridinilazole was very potent against all isolates collected in the US with an MIC 90 of 0.25 mcg/ml, including against all the hypervirulent ribotypes as well as those isolates with antibiotic resistances to other antibiotics in the test panel.

Conclusion
Ridinilazole showed excellent in-vitro activity against C. difficile isolates in the US, independent of ribotype. There has been a striking change in ribotype distribution compared to 2016, accompanied by a reduction in C. difficile resistance to moxifloxacin and imipenem.

Disclosures
Cheleste M. Thorpe, MD, Actelion: Grant/Research Support|Deinove: Advisor/Consultant|General Mills: Grant/Research Support|Merck: Grant/Research Support|Pfizer: Grant/Research Support|Summit: Advisor/Consultant|Summit: Grant/Research Support Stuart Johnson, M.D., Ferring Pharmaceuticals: Membership on Ferring Publication Steering Committee|Ferring Pharmaceuticals: Employee|Summit Plc: Advisor/Consultant Dale N. Gerding, MD, Destiny Pharma plc.: Advisor/Consultant Karen C. Carroll, MD, Abbott Diagnostics: Advisor/Consultant|BD Diagnostics: Advisor/Consultant|BD Diagnostics: Grant/Research Support|BioRad, Inc: Grant/Research Support|Meridian Biosciences: Grant/Research Support|Roche Diagnostics: Advisor/Consultant|Scanogen, Inc: Advisor/Consultant|Scanogen, Inc: Grant/Research Support|Thermo Fisher, Inc: Advisor/Consultant Kevin W. Garey, PharmD, MS, Acurx: Grant/Research Support|cidara: Advisor/Consultant|cidara: Grant/Research Support|Paratek: Grant/Research Support|Seres Health: Grant/Research Support|Summit: Grant/Research Support Esther Duperchy, PhD, Summit Plc: Employee David R. Snydman, MD, Merck: Advisor/Consultant|Merck and Company: Grant/Research Support|Prolacta: Advisor/Consultant|Prolacta: Grant/Research Support|Seres: Advisor/Consultant|Seres Health: Grant/Research Support|Summit Plc: Grant/Research Support|Takeda: Advisor/Consultant|Takeda: Grant/Research Support|Visterra: Advisor/Consultant.