Verification of direct methods for detection of carbapenemase producing Enterobacteriaceae from blood cultures

Abstract

Background: The aim of the study was to evaluate blood modified carbapenem inactivation method (mCIM) and automated susceptibility via VITEK2 compact system directly from positive blood culture bottles. Methods: The study was carried out using 54 strains positive for carbapenemase genes (OXA-48 type, KPC-type, NDM-type, and VIM-type) by multiplex PCR and 30 strains negative for these genes as controls, these strains were inoculated into blood culture bottles and then tested phenotypically for carbapenem resistance by mCIM and Vitek2 AST directly from the blood culture bottle. Results: MCIM was positive for all tested CPE strains and negative for the control strains with a 100% sensitivity, specificity and agreement with the PCR results. While vitek2 system had a sensitivity of 96%. Conclusion: Both methods save time when performed directly from the blood culture bottle that should guide appropriate administration of antimicrobials targeting bloodstream infections caused by carbapenemase producing Enterobacteriaceae. The mCIM is superior in being inexpensive requires basic reagents available in all microbiology laboratories with minimal processing compared to other tests and gives positive results with different  carbapenemase classes.