Why NDM Carbapenemases Are Spreading in AMR Gram-Negative Infections

"Why NDM Carbapenemases Are Spreading in AMR Gram-Negative Infections" takes up the question of what makes New Delhi metallo-beta-lactamase such a formidable threat. New Delhi metallo-beta-lactamase (NDM) has become a defining threat in gram-negative resistance because of how quickly it has spread and diversified, yet it has not displaced the KPC problem clinicians already know. Dr. Tamma opens with national surveillance data showing a steep rise in NDM-producing Enterobacterales across multiple states, including New York City, where NDM has overtaken KPC as the predominant carbapenemase.

Dr. Shields traces NDM from its first description in the late 2000s to its current presence across dozens of bacterial species and roughly 100 variants. He explains that no commercially available beta-lactamase inhibitor targets NDM, and that while metallo-beta-lactamases spare aztreonam, NDM frequently travels on plasmids alongside serine beta-lactamases that hydrolyze it, which is why aztreonam alone is not a reliable answer. The panel then explores the properties behind NDM's success. Dr. Shields describes its mobility across transposons and diverse plasmid types, contrasting it with the largely clonal global spread of KPC. Dr. Tamma adds that NDM anchors to the outer membrane, resists degradation, can be packaged into outer membrane vesicles for transfer between species, and in newer variants requires less zinc to remain active.

Dr. Haidar reflects that NDM producers are harder to treat and less predictable than KPC producers, and that he now considers them regularly in a health system where they were once an afterthought. Dr. Shields notes cases without classic risk factors, suggesting community transmission. Dr. Pogue closes with a counterpoint, emphasizing that KPC rates have held steady rather than declining. Clinicians therefore need to keep both carbapenemases on their radar, because the therapeutic considerations for each are fundamentally different.

Next, Dr. Pogue and Dr. Shields weigh the evidence and logistics behind "Aztreonam-Avibactam for AMR NDM-Producing Enterobacterales."