A new report from the Centers for Disease Control and Prevention on the deadly drug-resistant bacteria NDM-CRE found a 70% rise in infections in the U.S. between 2019 and 2023. Also known as "nightmare bacteria," NDM-CRE has few effective treatment options and high mortality rates. Brenda Wilson is a professor of microbiology at the University of Illinois Urbana-Champaign and author of the book "Revenge of the Microbes: How Bacterial Resistance is Undermining the Antibiotic Miracle." She talked with News Bureau biomedical sciences editor Liz Ahlberg Touchstone about what causes antimicrobial resistance, NDM-CRE and what steps can be taken to try to slow the spread of antimicrobial resistance.
How do microbes become resistant to antimicrobial agents in the first place?
In any bacterial community there is already a significant portion that are either resistant to or are more tolerant of the presence of antibiotics. When a bacterial population is treated with antibiotics, most of the bacteria in the community indeed will be killed - but, unfortunately, the drug-resistant or drug-tolerant bacteria can survive, grow and then dominate the community.
One of the biggest problems that we are now facing is the spread of antibiotic resistance to bacteria that did not previously have their own resistance. The genes that enable a bacterium to be resistant to a particular antibiotic or class of antibiotics often can be transferred to other nearby bacteria, giving these other bacteria new antibiotic resistance properties. Unfortunately, this gene transfer ability is quite prevalent and can transfer multiple different antibiotic resistance genes, such that some bacteria can acquire multiple resistances.
How big of an emerging problem is this?
Based on estimates from over 200 countries, a study published last year by the Institute for Health Metrics and Evaluation reported that over 1 million annual deaths were attributed to antimicrobial-resistant bacterial infections in 2021. Projections by this study and others anticipate annual deaths from resistant infections to increase to 8-10 million by 2050 with an economic healthcare burden of $100 trillion.
Unfortunately, there are now many bacteria and fungi that are considered multidrug resistant, extensively drug resistant or pan-resistant - that is, they do not respond to any of the common drugs used to treat these infections. Currently, the CDC lists 18 of the most alarming antimicrobial-resistant threats, with six of the 18 costing the U.S. about $5 billion annually. Health care providers must resort to second- and third-choice drugs for treatment when the bacteria are resistant to first-line drugs of choice. Unfortunately, these alternative lines of drugs are often less effective, more toxic and more expensive.
People with antimicrobial-resistant infections require increased time in the hospital for recovery, incur increased medical expenses, more often have severe morbidities and more often die from the infection. Treatment strategies often require combined therapies and altering the timing and dose of the drugs available.
What is the NDM-CRE "nightmare bacteria" the CDC recently issued a report about?
NDM-CRE, or "nightmare bacteria," are a type of Enterobacterales bacteria that are resistant to the drug carbapenem. Carbapenem antibiotics are a "last resort" class of broad-spectrum antibiotics that are used to treat severe infections, for which other commonly used antibiotics do not work. They have the New Delhi metallo-β-lactamase gene, or NDM, making the already multidrug-resistant bacteria now resistant to nearly all antibiotics commonly used to fight these infections. This resistance severely limits treatment options, often leaving none or only a few expensive, IV-administered antibiotics effective against the infection.
NDM-CRE infections are associated with high mortality rates - up to 40-50% - because they often cannot be treated soon enough due to the clinicians needing to find a drug that works. The CDC report has prompted health officials to urge increased testing, stricter infection control and careful antibiotic selection to prevent further spread.
Are there other CRE bacteria or "superbugs" that the CDC is tracking?
Yes. The two most common types of CRE bacteria in the U.S. are carbapenem-resistant Klebsiella species and carbapenem-resistant E. coli. These infections are usually spread in health care settings among more vulnerable patients.
The term "superbug" has been ascribed to several of the top 18 threats listed by the CDC. Two examples of "superbugs" are Mycobacterium tuberculosis, the cause of tuberculosis, and Acenitobacter baumannii, a newly emerged pathogen. Both of these bacteria are naturally resistant to many commonly used antibiotics, but now strains are emerging that are resistant to nearly all antibiotics and even some last-resort drugs. In 2021 Illinois had 254 cases of TB, four of which were multidrug resistant. In 2015, Illinois even had one case of extensively drug-resistant TB.
As far as fungal infections, there is emerging a particularly frightening multidrug-resistant fungus, Candida auris. In 2019, 175 cases of C. Auris were reported in Chicago, and Illinois has had 1,044 cases since then.
What steps can people take to avoid adding to the rise of antimicrobial resistance?
There is an urgent need to improve understanding of appropriate antibiotic usage and stewardship. The major factors that contribute to antimicrobial resistance include the widespread release of antibiotics into the environment that increase the selective pressure of bacteria to acquire resistance genes to survive. This includes things like sewage and agricultural runoff, but also individual health choices, such as overprescription or incorrect prescription by doctors and noncompliance with dosing regimens by patients.
Educational efforts are needed for health professionals, agricultural industry stakeholders, patients and consumers that emphasize proper antibiotic use and preventive medicine such as good hygiene practices, vaccines, clean water, good nutrition and healthy lifestyles. We need to stop or more strictly regulate over-the-counter antibiotic sales and indiscriminate agricultural use. We need to improve water quality, sanitation, and hygiene to reduce disease and prevent antimicrobial resistance spread.
