A new CDC report shows infections caused by multi-drug-resistant bacteria nicknamed “nightmare bacteria” surged in the United States from 2019 to 2023. Carbapenem-resistant Enterobacterales (CRE) — which include E. coli and Klebsiella pneumoniae — are resistant to carbapenems, a last-line class of broad-spectrum antibiotics used for severe infections. Within CRE, carbapenemase-producing CRE (CP-CRE) are especially dangerous because they produce an enzyme, carbapenemase, that breaks down these antibiotics, leaving clinicians with few treatment options.
The CDC study, published in Annals of Internal Medicine, identified New Delhi metallo-β-lactamase–producing CRE (NDM-CRE) as the main driver of new infections. NDM-CRE is resistant even to some newer drugs developed for carbapenem-resistant infections. From 2019 to 2023, CP-CRE clinical cultures reported by U.S. surveillance networks across 29 states — covering more than one-third of the U.S. population — rose by 69%, while NDM-CRE incidence rose by 461%.
This rise is particularly concerning because CP-CRE and NDM-CRE are difficult to treat and can cause pneumonia, bloodstream infections, wound infections, meningitis, and urinary tract infections. A separate CDC estimate attributed 12,700 infections and 1,100 deaths to CRE in 2020. NDM-CRE can also transfer resistance genes to other bacteria, allowing rapid spread of resistance across species.
CP-CRE transmission occurs mainly in hospitals and healthcare settings and is less likely in the general community. The infections are occurring among very ill patients; the increased rates are concentrated in healthcare facilities. People at highest risk include those who require a ventilator, use invasive medical devices (urinary or intravenous catheters), receive prolonged courses of antibiotics, or have weakened immune systems.
Symptoms vary by site of infection; there are no specific signs unique to CRE. It may present as urinary tract infection symptoms, respiratory infection or pneumonia, bloodstream infection, wound infection, or meningitis. Early detection is critical to choose appropriate therapy, which must be tailored to the specific carbapenemase type and to patient factors like kidney or liver function and allergies.
CRE spreads by direct contact with infected or colonized people, contaminated surfaces, and medical equipment; rare animal-to-human transmissions have been documented. Both people and animals can carry CRE without symptoms (colonization), potentially passing it to others.
Preventing CRE in healthcare settings requires surveillance (identifying, reporting, and tracking cases), strict hygiene and sanitization of surfaces and instruments, and rigorous handwashing. Even healthy visitors and caregivers should practice meticulous hand hygiene in hospitals and care facilities, especially when caring for immunocompromised or elderly patients.
Antimicrobial resistance (AMR) refers to microbes — bacteria, viruses, fungi, and parasites — becoming resistant to drugs that previously controlled them. Often called a “silent pandemic,” AMR is a growing crisis with limited public awareness. A 2024 Lancet forecast estimated that by 2050 up to 39 million people could die from antibiotic-resistant infections, with about 1.91 million deaths in that year alone.
To combat AMR, public health organizations including the CDC and WHO support antimicrobial stewardship programs to improve antibiotic prescribing and reduce overuse. Stewardship has advanced in recent years through interdisciplinary teams, better diagnostic tools, and improved research, which help clinicians choose appropriate therapies and slow the spread of resistance.
