Assessing Vancomycin and Metronidazole Susceptibility for CDI

Although CDI remains the most common healthcare-associated infection, antimicrobial resistance surveillance for C difficile remains limited.

As such, a team at the University of Houston College of Pharmacy examined hospitalized CDI patient samples from 2 Greater Houston Area health systems to further understand potential vancomycin (VAN) and metronidazole (MTZ) resistance.

“Of 355 isolates analyzed, 18% and 26% were resistant to MTZ and VAN, respectively,” the investigators wrote. “MTZ MICs ranged from 0.25 – 8 mg/L, with a MIC50 of 0.25 mg/L and a MIC90 of 2 mg/L. VAN MICs ranged from 0.5 – 16 mg/L, with a MIC50 of 2 mg/L and a MIC90 of 4 mg/L. RT F027 demonstrated increased resistance to both VAN and MTZ. A subgroup analysis based on location exhibited numerically higher susceptibility rates at community institutions versus hospitals in the TMC.”

The study, “A Multi-institutional C difficile Antibiogram for Vancomycin and Metronidazole Susceptibility,” was presented at the 24th Annual Making a Difference in Infectious Disease (MAD-ID) Meeting 2022 in Orlando, Florida from May 18-21.

Contagion spoke to study coauthor Taryn Eubank, PharmD, BCIDP, Infectious Diseases Research fellow, University of Houston College of Pharmacy at the MAD-ID meeting who provided insights on the study and some of the takeaways looking at susceptibility testing.