Between 2019 and 2023, the prevalence of NDM-producing carbapenem-resistant Enterobacterales (NDM-CRE) in the United States skyrocketed by 461 percent. These bacteria, which are notoriously difficult to treat because they resist even the most potent antibiotics, were once rare. Now, they are a fixture of the American healthcare landscape.

For years, the question was whether this surge was a diffuse, random phenomenon or a targeted, manageable threat. New data presented this week at the ASM Microbe 2026 conference provides the answer: it is the latter. By decoding the genetic blueprints of more than 8,000 NDM-CRE samples, CDC researchers have confirmed that the crisis is being driven by a small, predictable group of "high-risk clones."

The Genetic Blueprint of an Outbreak

The investigation, led by the CDC’s Division of Healthcare Quality Promotion in collaboration with the Antimicrobial Resistance Laboratory Network (AR Lab Network), utilized whole genome sequencing to map the evolution of these pathogens. The findings are stark. Roughly 50 percent of the cases were traced to Klebsiella pneumoniae, while another 31 percent were linked to Escherichia coli.

These are not random environmental bacteria. They are well-documented hospital-associated pathogens that have evolved to carry the NDM gene, which confers resistance to carbapenems—a class of antibiotics often reserved as a last resort for severe infections.

"The spread of these nearly untreatable bacteria is being driven by a small number of highly successful bacterial strains that have acquired NDM," said Richard Stanton, Ph.D., a bioinformatician at the CDC. "New resistant strains can emerge quickly once they acquire these genes."

The Emergence of ST45

Perhaps the most concerning discovery in the genomic data is the rapid rise of a specific K. pneumoniae lineage known as ST45. This clone only began to appear in the surveillance data in 2022, yet it has already established itself as a significant threat.

ST45 appears to be a master of adaptation, carrying a plasmid—a mobile piece of DNA—that allows it to share drug-resistance genes with other bacteria. This ability to "trade" resistance markers means that even if hospitals manage to contain one strain, the genetic machinery for resistance can jump to another, effectively staying one step ahead of clinical interventions.

Key Takeaways

  • Concentrated Threat: The 461% increase in NDM-CRE is not a random spike; it is driven by a handful of "high-risk" bacterial clones, primarily K. pneumoniae and E. coli.
  • Genomic Surveillance Works: The AR Lab Network’s use of whole genome sequencing across all 50 states allowed researchers to identify the emergence of the ST45 lineage in near real-time.
  • Strategic Pivot: Because the spread is concentrated in specific clones, the CDC is shifting its focus toward targeted diagnostics and infection control protocols specifically designed to neutralize these high-risk lineages.

What Experts Say

Public health officials argue that the era of broad, generalized infection control is ending. Instead, the focus must shift toward precision surveillance. By identifying these high-risk clones the moment they enter a hospital system, labs can trigger specialized containment protocols before a localized cluster becomes a regional outbreak.

"Additional, new high-risk clones can also rapidly emerge, making it important to recognize these emerging threats through genomic surveillance," Stanton noted. The goal is to move from reactive reporting to proactive identification, using the AR Lab Network to flag these specific genetic signatures as soon as they appear in patient samples.

As the CDC continues to integrate this genomic data into state-level public health responses, the next critical test will be the implementation of these findings in hospital clinical workflows. By the end of 2026, the agency expects to have standardized protocols in place that allow local labs to use this sequencing data to trigger immediate, targeted isolation procedures, effectively closing the window of opportunity for these high-risk clones to move from patient to patient.