New Delhi Metallo-Beta-Lactamase (NDM) Infections
NDM infections are caused by bacteria producing the New Delhi metallo-beta-lactamase enzyme, which confers resistance to almost all beta-lactam antibiotics including carbapenems, creating a serious public health threat with limited treatment options. 1, 2
What is NDM?
- NDM (New Delhi metallo-beta-lactamase) is a metallo-β-lactamase enzyme first identified in 2007 in a patient who had been hospitalized in New Delhi, India 1
- It belongs to Class B metallo-β-lactamases (MBLs) that require zinc ions for their catalytic activity 3
- Currently, at least 40 NDM variants have been identified across the globe due to amino acid substitutions 4
- NDM enzymes are typically encoded on plasmids (mobile genetic elements) that can be easily transmitted between different bacterial species 1, 2
Bacteria Carrying NDM
- NDM has been identified in over 60 bacterial species across 11 bacterial families 2
- The predominant carriers are Klebsiella pneumoniae and Escherichia coli 2
- Common sequence types for K. pneumoniae carrying NDM include ST11, ST14, ST15, and ST147 2
- Common sequence types for E. coli carrying NDM include ST167, ST410, and ST617 2
- The enzyme can be transmitted to other Enterobacteriaceae and other genera of bacteria 1
Epidemiology
- NDM-producing bacteria have been identified worldwide with highest prevalence in:
- The Indian subcontinent
- The Middle East
- The Balkans 2
- Most blaNDM-carrying plasmids belong to limited replicon types (IncX3, IncFII, or IncC) 2
- In the United States, NDM cases are still relatively rare but increasing 1
- International travel and hospitalization in endemic regions are significant risk factors 1
Clinical Significance
- NDM-producing bacteria can cause various infections including:
- Urinary tract infections
- Bloodstream infections
- Pneumonia
- Wound infections 1
- These infections are associated with high mortality rates due to limited treatment options 5
- NDM-producing bacteria often carry multiple resistance determinants, making them resistant to many other antibiotic classes beyond beta-lactams 2
Detection
- Commonly used phenotypic tests cannot specifically identify NDM 2
- Lateral flow immunoassays can specifically detect NDM 2
- Molecular approaches remain the reference methods for detecting blaNDM genes 2
- Modified Hodge test may be weakly positive but is not specific for NDM 1
- Rapid testing to identify specific carbapenemase families (KPC, NDM, VIM, OXA-48-like) is strongly recommended to guide appropriate treatment 1
Treatment Options
- For infections caused by metallo-β-lactamase (MBL)-producing CRE, including NDM:
- Most NDM-producing isolates are only susceptible to limited antibiotics such as:
- Tigecycline
- Colistin
- Polymyxin B 1
- Combination therapy is often required for severe infections 1
- No specific NDM inhibitors have been approved for clinical use 2
Infection Control
- Aggressive infection control measures are essential to prevent spread 1
- Key infection control strategies include:
- Contact precautions (gowns and gloves) for all patient care 1
- Dedicated medical equipment 1
- Enhanced environmental cleaning 1
- Point-prevalence surveys of epidemiologically linked patients 1
- Active surveillance in high-risk units 1
- Limiting unnecessary antibiotic exposure through antimicrobial stewardship 1
- Patients with history of NDM colonization or infection should have their medical records flagged for future admissions 1
- Healthcare facilities should avoid exposing wounds, injection sites, and catheters to tap water, as water systems can harbor these organisms 1
Public Health Implications
- NDM-producing bacteria represent a severe challenge in healthcare settings 2
- Economic burden is significant due to prolonged hospitalizations and limited treatment options 5
- Coordinated efforts between healthcare facilities are required for effective management 5
- U.S. and international efforts to control carbapenem-resistant Enterobacteriaceae (CRE) are critical to protect public health 1