Reduced Vancomycin Susceptibility in C difficile Leads to Worse Patient Outcomes

The use of oral vancomycin to treat Clostridioides difficile infection (CDI) has increased recently, which may lead to the development of resistance. Previous research showed that mutations in the VanSR system can cause increased resistance to vancomycin and decreased effectiveness in vitro.

One study, presented as an abstract at this week’s 2023 MAD-ID Annual Antimicrobial Stewardship Meeting, sought to describe the epidemiology of reduced vancomycin susceptibility in clinical isolates and its impact on CDI patient outcomes.

The study was presented by lead author Taryn Eubank, PharmD, BCIDP, and recruited adult patients hospitalized with CDI. Included patients were hospitalized in 1 of 14 hospitals across the Houston area between 2017-2021. The patients were treated with vancomycin monotherapy, initiated within 48 hours of CDI diagnosis.

The investigators collected and analyzed stool samples for reduced vancomycin susceptibility, defined by minimum inhibitory concentrations (MIC) >2 mg/L. MICs were measured by agar dilution, in accordance with Clinical & Laboratory Standards Institute (CLSI) guidelines.

The other study objective was a 30-day sustained clinical response (SCR), defined as a composite endpoint of day 14 cure, absence of 30-day disease recurrence, and being alive at day 30.

A total of 300 isolates were collected, and of them, 102 (34.4%) exhibited reduced vancomycin susceptibility. At 18% (n = 54), ribotype F027 was the most common in the cohort and had the highest rate of reduced susceptibility at 77.4% (n = 41).

Patients with severe or fulminant disease and non-susceptible strains had significantly lower 30-day sustained clinical response rates. VanSR mutations were found in a majority of isolates, suggesting a molecular mechanism for the reduced susceptibility.

The investigators concluded that a high proportion of clinical C diff isolates exhibited heightened MICs to vancomycin. They emphasized the need for further research to better understand these mechanisms.

This study, “Reduced Vancomycin Susceptibility in Clostridioides difficile is Associatedwith Lower Rates of 30-day Sustained Clinical Response,” was presented as an abstract at the 2023 MAD-ID Annual Antimicrobial Stewardship Meeting.