Zeyu FuFollow

Date of Award

January 2023

Document Type

Open Access Thesis

Degree Name

Master of Public Health (MPH)


School of Public Health

First Advisor

Melinda M. Pettigrew


AbstractIntroduction: The emergence of vancomycin-resistant strains of C. difficile has become a growing concern, as it can lead to treatment failure and increased morbidity and mortality. In this study, we aimed to investigate the prevalence and mechanisms of vancomycin resistance in C. difficile isolates in Connecticut from patients with confirmed C. difficile infection at Yale New Haven Hospital. Methods: We collected 89 stool samples from patients with confirmed C. difficile infection, isolated C. difficile, and performed susceptibility testing on the isolates using the E-strip test method. Isolates with an MIC value below 4 μg/ml were classified as susceptible and isolates with an MIC value above 4 μg/ml were classified as resistant. Whole-genome sequencing (WGS) and gene analysis was performed on 19 isolates and the samples were screened for the presence of vancomycin resistance genes. Results: Antimicrobial susceptibility results showed that the majority of isolates (80/89) are vancomycin susceptible (MIC < 4 μg/ml). Of the remaining 9 vancomycin-resistant isolates, only one had extreme high-level resistance (>256 µg/mL), while the other 8 isolates had low-level resistance. However, we found that only two of the 8 low-level resistant isolates were C. difficile, while the other 6 were either mixed cultures or mis-identified, primarily Enterococcus faecalis (5 isolates). Conclusion: The majority of C. difficile strains are susceptible to vancomycin. The apparent high prevalence of high-level vancomycin-resistant C. difficile may have resulted due to isolation techniques that mis-identify C. difficile. Our study highlights the need for improved methods of isolating C. difficile from stool samples and the importance of implementing proper antimicrobial stewardship practices and surveillance to combat the growing threat of antibiotic resistance in C. difficile infections.


This is an Open Access Thesis.

Open Access

This Article is Open Access