CDC Warns of Sharp Rise in Drug-Resistant ‘Nightmare Bacteria’

• A new CDC report found a sharp increase in infections caused by a dangerous “nightmare bacteria.”
• Carbapenemase-producing carbapenem-resistant Enterobacterales (CP-CRE) are bacteria capable of neutralizing powerful antibiotics.
• CP-CRE bacteria are very difficult to treat and potentially deadly, capable of causing pneumonia and bloodstream infections, among other symptoms.

A new CDC report shows that infections caused by multi-drug-resistant bacteria known colloquially as “nightmare bacteria” surged in the United States from 2019 to 2023.

Carbapenem-resistant Enterobacterales (CRE), which include bacteria such as E. coli and Klebsiella pneumoniae, are resistant to carbapenems, a “last line” class of broad-spectrum antibiotics used to treat severe infections, including those caused by other drug-resistant bacteria.

Within CRE exists an even more dangerous subset of bacteria known as carbapenemase-producing carbapenem-resistant Enterobacterales (CP-CRE). These variants produce an enzyme called carbapenemase, which enables them to break down carbapenem antibiotics, neutralizing the drugs before they can work, leaving doctors with limited options for treatment.

The CDC report, published in Annals of Internal Medicine, identified a specific type of CP-CRE, known as New Delhi metallo-β-lactamase (NDM-CRE), as the major driver of new infections. NDM-CRE is resistant to newer antibiotics developed specifically for the treatment of carbapenem-resistant infections.

Between 2019 and 2023, CP-CRE clinical cultures reported by US surveillance networks in 29 different states — and representing more than one-third of the U.S. population — rose by 69%. Across that same timeframe, the incidence of NDM-CRE infections increased by 461%.

“This sharp rise is concerning as we face a growing threat that limits our ability to treat some of the most serious bacterial infections that patients can get,” Danielle A. Rankin, PhD, an epidemiologist at the CDC and first author of the report, told Healthline.

A separate CDC report estimated that CRE was responsible for 12,700 infections and 1,100 deaths in 2020.

In addition to being harder to treat due to the presence of the carbapenemase enzyme, NDM-CRE is also capable of spreading its genes to other bacteria, including different species, allowing them to rapidly acquire resistance. As more bacteria acquire resistance, the infection becomes more difficult to contain.

Under normal circumstances, CP-CRE infection is unlikely for healthy individuals. Like other drug-resistant bacteria, CP-CRE spreads primarily in hospitals and other healthcare environments.

“This increase that we’re seeing is within patients in healthcare facilities. This is not in the community, this is among our sickest-of-sick patients,” Rankin said.

Individuals most at risk for CP-CRE infection are those who:

• require a ventilator to breathe
• use invasive medical devices, such as urinary or intravenous catheters
• are already taking long courses of antibiotics
• have weakened immune systems

CP-CRE can affect different systems in the body defending on the site of the infection, so it may present in a variety of different ways.

“There are no specific symptoms to CRE,” Rankin said.

• bloodstream infections
• wound infections
• meningitis

CP-CRE is resistant to nearly all available antibiotics. Due to how difficult it is to treat, surveillance and prevention are important factors in mitigating the risks of this devastating infection.

“Detecting these infections early and quickly is imperative to prevent further complications, including mortality. This allows us to choose the appropriate antibiotic, which must be tailored to the carbapenemase type,” said Marnie L. Peterson, PharmD, PhD, outreach coordinator for Antimicrobial Stewardship with the Center for Infectious Disease Research and Policy (CIDRAP) at the University of Minnesota. Peterson wasn’t involved in the CDC report.

“Limited antibiotic options mean a complicated decision for clinicians in customizing antibiotics to the patient’s specific conditions, such as renal and hepatic insufficiencies or allergies,” she added.

Both humans and animals can unknowingly carry CRE on their bodies without showing symptoms, passing it to others in a process known as colonization.

Preventing the spread of CRE in healthcare facilities relies on a multi-pronged approach that includes surveillance (i.e., identifying, reporting, and tracking), as well as hygiene and sanitization of surfaces and tools.

Regular handwashing is one of the most important things individuals can do to limit the spread.

Even otherwise healthy individuals should be meticulous with hand hygiene in hospitals and care facilities.

“Healthy individuals are part of this strengthened awareness and prevention strategy. They should be aware of the increasing risk of antibiotic resistance due to NDM-CRE and prevention, especially if they are caregivers to immunocompromised and elderly individuals,” Peterson said.

Antimicrobial resistance (AMR) is a broad term that describes when different microbes (bacteria, viruses, fungi, and parasites) develop resistance to drugs designed to kill them.

This phenomenon is frequently called the “silent pandemic,” because it is a growing healthcare crisis with little public awareness.

While C. diff itself is typically not a resistant bacterium, it causes infection by exploiting dysregulation of the gut microbiome caused by antibiotic usage.

A systematic forecast published in The Lancet in 2024 estimated that 39 million people could die from antibiotic-resistant bacterial infections by 2050. In that year alone, an estimated 1.91 million people could die from bacterial AMR, an increase of nearly 70% per year compared to 2021.

To combat this “silent pandemic,” major public health organizations, including the CDC and WHO, have invested in antimicrobial stewardship — efforts aimed at improving antibiotic prescribing practices and reducing overuse.

“Antibiotic stewardship has progressed exponentially in the past five years due to the formation of interdisciplinary teams who have access to better testing and diagnostic tools, as well as improved research methodologies,” said Peterson.