How to detect NDM-1 producers.

Area of Science:

• Microbiology
• Infectious Diseases
• Antimicrobial Resistance

Background:

• New Delhi metallo-beta-lactamase 1 (NDM-1) producing Enterobacteriaceae are increasingly prevalent worldwide.
• These NDM-1 producers can act as both pathogens and colonizers of normal flora, posing challenges for infection control.
• Effective screening methods are crucial to identify and manage the spread of NDM-1 producing bacteria.

Purpose of the Study:

• To evaluate the efficacy of different culture media for screening NDM-1 producing Enterobacteriaceae.
• To identify reliable methods for detecting NDM-1 producing strains in clinical settings.
• To assess the role of NDM-1 producers as colonizers and pathogens for infection control purposes.

Main Methods:

• Twenty-seven NDM-1 positive Enterobacteriaceae isolates of global origin were analyzed.
• Antimicrobial susceptibility testing was performed, including combined disk diffusion (IMP/IMP + EDTA) and Etest MBL.
• Automated Vitek2 system and PCR with specific primers were used for verification of NDM-1 production.
• ChromID ESBL and CHROMagar KPC culture media were evaluated for their detection capabilities.

Main Results:

• Susceptibility to carbapenems varied among the NDM-1 producing isolates.
• Combined disk diffusion, Etest MBL, and Vitek2 accurately identified NDM-1 producers, confirmed by PCR.
• ChromID ESBL demonstrated excellent detection levels with low limits of detection (8 × 10^0 to 5 × 10^2 CFU/ml).
• CHROMagar KPC showed higher limits of detection (1 × 10^1 to 5 × 10^5 CFU/ml) but is suitable for outbreak follow-up.

Conclusions:

• ChromID ESBL is a highly effective medium for screening NDM-1 producing Enterobacteriaceae carriers.
• CHROMagar KPC can be utilized for monitoring NDM-1 producer outbreaks.
• Molecular methods provide reliable verification of NDM-1 producing colonies identified on screening media.