Antibiotic disc agar plates following enrichment broth versus direct plating onto ChromID® agar plates for surveillance of multidrug-resistant bacterial colonization: A comparative prospective study.

Abstract

Introduction: It remains unclear whether incorporating a pre-enrichment step in broth media enhances the sensitivity of culture-based methods for recovering multidrug-resistant organisms (MDRO) from surveillance swabs specimens.

Methods: This prospective study included 364 surveillance swabs specimens. The performance of antibiotic disc agar plates following enrichment broth was compared with direct plating onto ChromID® agar plates. Additionally, 17 specimens were tested by the BIOFIRE® Blood Culture Identification 2 (BCID2) Panel to assess its added value for MDRO detection.

Results: ESBL-producing Enterobacterales were recovered from 35/288 specimens after enrichment in broth and from 33/288 specimens using ChromID® ESBL agar. Carbapenemase-producing organisms were recovered from 7/288 specimens following enrichment and from 6/288 specimens using ChromID® bi-plate CARBA SMART. Vancomycin-resistant enterococci (VRE) were recovered from 7/288 specimens after enrichment and from 3/288 specimens using ChromID® VRE agar. Molecular testing additionally detected two VRE isolates missed by culture-based methods.

Conclusion: Pre-enrichment in broth media mostly increases VRE detection while no substantial improvement was observed for the recovery of ESBL- or carbapenemase-producing bacteria.