What does NDM (New Delhi metallo-beta-lactamase) stand for?

NDM (New Delhi Metallo-Beta-Lactamase) Definition and Significance

NDM stands for New Delhi metallo-beta-lactamase, which is a metallo-β-lactamase enzyme first identified in 2007 in a patient who had been hospitalized in New Delhi, India. 1

Characteristics of NDM

• NDM enzymes are typically encoded on plasmids (mobile genetic elements) that can be easily transmitted between different bacterial species, contributing to their rapid global spread 1
• NDM belongs to Class B metallo-β-lactamases (MBLs) in the Ambler classification system, alongside other MBLs such as VIM and IMP 2
• NDM-producing bacteria have been identified worldwide with highest prevalence in the Indian subcontinent, though cases are increasing globally 1
• Currently, 40 NDM variants have been identified in different bacterial strains across the globe due to substitutions of single or multiple amino acids 3

Clinical Significance

• NDM enzymes confer resistance to carbapenems and almost all β-lactam antibiotics, with the exception of monobactams (aztreonam) 4, 5
• NDM-producing bacteria are particularly worrisome due to their ability to hydrolyze all classes of β-lactams and the inability of classic serine β-lactamase inhibitors to inhibit them 2
• NDM is often associated with resistance to many other classes of antibiotics, creating multidrug-resistant or even pan-resistant infections 5, 6
• NDM-producing bacteria can cause various infections including:
  • Urinary tract infections 1
  • Bloodstream infections 1, 6
  • Pneumonia 1
  • Wound infections 1

Diagnostic Considerations

• Rapid testing should be used to identify specific carbapenemase families (including NDM) in carbapenem-resistant Enterobacterales (CRE) to guide appropriate treatment 2
• Commonly used phenotypic tests cannot specifically identify NDM, requiring molecular approaches as reference methods for detecting blaNDM 5

Treatment Implications

• Knowledge of the molecular mechanism responsible for carbapenem resistance is crucial because each class of enzymes confers variable susceptibility profiles requiring different treatment strategies 2
• For infections caused by NDM-producing bacteria, ceftazidime-avibactam combined with aztreonam is the preferred first-line treatment, showing significantly lower 30-day mortality rates (19.2% versus 44%) compared to other therapies 7
• Cefiderocol may also be considered as an alternative option for NDM-producing infections 7, 4
• Most NDM-producing isolates are only susceptible to limited antibiotics such as tigecycline, colistin, and polymyxin B 1

Infection Control

• Aggressive infection control measures are essential to prevent spread of NDM-producing organisms 1
• Key infection control strategies include contact precautions, dedicated medical equipment, enhanced environmental cleaning, and active surveillance in high-risk units 1

Understanding NDM and its implications is crucial for clinicians to appropriately diagnose, treat, and prevent the spread of these highly resistant organisms.