Evaluating Vancomycin Susceptibility Trends Against Clinical Enterococcus Faecalis Isolates in a New York City Health-system
Faculty Mentor
Jaclyn Cusumano, Olivia Gladys Funk
Major/Area of Research
Pharmacy, Infectious Disease
Description
Introduction: Enterococcus faecalis vancomycin resistance (VRE) is emerging, with mortality rates up to 21%. Isolates with elevated penicillin minimum inhibitory concentrations (MIC; 4-8 μg/mL) are more likely to be VRE, emphasizing the importance of understanding susceptibility patterns, and accurately predicting them. Our research aims to investigate the current susceptibility patterns of E. faecalis isolates against vancomycin and the predictability of MicroScan Walkaway.
Methods: Across a New York City health-system, 46 E. faecalis blood isolates were selected from July 2019 to June 2021. Of the isolates, 10 were penicillin-susceptible (MIC ≤2 μg/mL) and 36 were borderline penicillin-resistant (MIC 4-8 μg/mL), from which we chose 24 VRE isolates. Vancomycin MICs were determined via broth microdilution (BMD) per CLSI standards and were categorized as resistant, intermediate or susceptible (MIC ≥32 μg/mL, 8-16 μg/mL or ≤4 μg/mL, respectively). MIC susceptibility categories were compared between BMD and MicroScan Walkaway results in 44 isolates. Categorical agreement was the number of isolates with the same susceptibility interpretation. Errors were considered very major (susceptible by MicroScan, resistant by BMD), major (resistant by MicroScan, susceptible by BMD) or minor (intermediate by one, resistant/susceptible by the other). Acceptable performance was defined as ≤1.5% very major errors, ≤3.0% major errors or an overall category error ≤10%.
Conclusions: Overall, 52.2% of isolates were VRE, and of the borderline penicillin-resistant isolates, 66.7% were VRE. When determining the performance of MicroScan, The categorical agreement between MicroScan and BMD was 95.5%. There were two (4.5%) major errors and no very major or minor errors identified. Our findings show that about half of our isolates were VRE and we observed a positive correlation between VRE and borderline penicillin-resistant isolates. Overall, MicroScan did not demonstrate acceptable performance in predicting vancomycin MICs.
Evaluating Vancomycin Susceptibility Trends Against Clinical Enterococcus Faecalis Isolates in a New York City Health-system
Introduction: Enterococcus faecalis vancomycin resistance (VRE) is emerging, with mortality rates up to 21%. Isolates with elevated penicillin minimum inhibitory concentrations (MIC; 4-8 μg/mL) are more likely to be VRE, emphasizing the importance of understanding susceptibility patterns, and accurately predicting them. Our research aims to investigate the current susceptibility patterns of E. faecalis isolates against vancomycin and the predictability of MicroScan Walkaway.
Methods: Across a New York City health-system, 46 E. faecalis blood isolates were selected from July 2019 to June 2021. Of the isolates, 10 were penicillin-susceptible (MIC ≤2 μg/mL) and 36 were borderline penicillin-resistant (MIC 4-8 μg/mL), from which we chose 24 VRE isolates. Vancomycin MICs were determined via broth microdilution (BMD) per CLSI standards and were categorized as resistant, intermediate or susceptible (MIC ≥32 μg/mL, 8-16 μg/mL or ≤4 μg/mL, respectively). MIC susceptibility categories were compared between BMD and MicroScan Walkaway results in 44 isolates. Categorical agreement was the number of isolates with the same susceptibility interpretation. Errors were considered very major (susceptible by MicroScan, resistant by BMD), major (resistant by MicroScan, susceptible by BMD) or minor (intermediate by one, resistant/susceptible by the other). Acceptable performance was defined as ≤1.5% very major errors, ≤3.0% major errors or an overall category error ≤10%.
Conclusions: Overall, 52.2% of isolates were VRE, and of the borderline penicillin-resistant isolates, 66.7% were VRE. When determining the performance of MicroScan, The categorical agreement between MicroScan and BMD was 95.5%. There were two (4.5%) major errors and no very major or minor errors identified. Our findings show that about half of our isolates were VRE and we observed a positive correlation between VRE and borderline penicillin-resistant isolates. Overall, MicroScan did not demonstrate acceptable performance in predicting vancomycin MICs.