NDM-1 (New Delhi metallo-beta-lactamase)

  • Medical Author:

    Sandra Gonzalez Gompf, MD, FACP is a U.S. board-certified Infectious Disease subspecialist. Dr. Gompf received a Bachelor of Science from the University of Miami, and a Medical Degree from the University of South Florida. Dr. Gompf completed residency training in Internal Medicine at the University of South Florida followed by subspecialty fellowship training there in Infectious Diseases under the directorship of Dr. John T. Sinnott, IV.

  • Medical Editor: Charles Patrick Davis, MD, PhD
    Charles Patrick Davis, MD, PhD

    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

What Is CRE?

CRE (carbapenem-resistant Enterobacteriaceae) bacteria are members of related bacterial genera that are commonly found almost everywhere in the world, often colonizing humans and animals (living in or on humans and animals mucosal surfaces, gastrointestinal tracts, and on some areas on the skin). However, CRE possess a unique genetic makeup that allows the bacteria to make an enzyme that protects CRE bacteria from a powerful antibiotic: carbapenem. The most notable genera that can share and even transfer this genetic trait to other members of the Enterobacteriaceae are E. coli and Klebsiella pneumoniae. Because these bacteria generate similar problems for patients (especially treatment difficulties), most investigators simply group them together and term them CRE bacteria (some researchers term those bacteria that produce the enzyme carbapenemase CP-CRE bacteria). Similar types of components are termed KPC (Klebsiella pneumoniae carbapenemase) and NDM (New Delhi metallo-beta-lactamase).

NDM-1 facts

  • NDM-1 stands for a gene that produces New Delhi metallo-beta-lactamase in certain bacteria that cause infections. This is a substance that destroys the commonest types of antibiotics.
  • Bacteria with the NDM-1 gene are part of a larger group of superbug bacteria that are extremely hard to treat and can spread easily in hospitals. Most NDM-1 strains are resistant to all commonly used antibiotics.
  • Specific testing for NDM-1 is not routinely available.
  • NDM-1 has been reported most commonly from India and Pakistan. It is spreading throughout the world as people travel from country to country.
  • The first three cases of NDM-1 in the United States were reported in June 2010.
  • NDM-1 is carried by bacteria that commonly inhabit the bowel. Strains spread from person to person through contact with contaminated hands or items.
  • Washing or disinfecting hands frequently and wearing protective clothing in hospitals lowers the risk of spreading or getting NDM-1. In hospitals, hand hygiene is critical. Patients with NDM-1 are also placed in private rooms, and health-care workers wear gowns and gloves when entering.
  • To reduce the risk of resistant bacteria, doctors and hospitals must use antibiotics wisely and only when needed.
  • Bacteria that express NDM-1 usually have other resistance factors, such as carbapenemases. Thus, most NDM-1 strains are resistant to all commonly used antibiotics.
  • Routine antibiotic-sensitivity testing can detect resistance to beta-lactam antibiotics. Specific testing for NDM-1 is not routinely available. Fortunately, it is not necessary to determine if carbapenem resistance is specifically due to NDM-1 because treatment is guided by the antibiotic-sensitivity testing.

What is NDM-1?

Antibiotics are medicines that kill bacteria (not viruses or fungi). There are different groups of antibiotics, based on how they work to kill bacteria. Beta-lactam antibiotics (or beta-lactams) are the largest group of antibiotics used against common infections. Carbapenems are another class of antibiotics typically used as a last resort when beta-lactams no longer work.

When bacteria are no longer killed by an antibiotic, they are called resistant to that antibiotic. Some bacteria are resistant to so many antibiotics there are few or no treatments left. These are often called "superbugs."

The beta-lactam group includes penicillins and cephalosporins. There are many types of beta-lactamases. Bacteria can become resistant by producing substances that destroy beta-lactams; these are beta-lactamases. The carbapenem antibiotics are destroyed by carbapenemases. Few bacteria have resistance to carbapenems. Carbapenems are often the last resort antibiotic for resistant bacteria that beta-lactams can no longer kill.

NDM-1 stands for the carbapenemase New Delhi metallo-beta-lactamase-1. It is produced by bacteria containing the resistance gene blaNDM-1. There are many types of carbapenemases that destroy penicillins, cephalosporins, and the last resort carbapenems, mostly produced by a large group of bacteria called Enterobacteriaceae. These carbapenemase-producers are also called carbapenem-resistant Enterobacteriaceae or CRE bacteria. NDM-1 bacteria are only one of the many CRE that threaten health today.

NDM-1 infection was first recognized in 2009, in residents or travelers from India and Pakistan. Antibiotic use in India is poorly restricted, and it appears likely that overuse of carbapenems allowed NDM-1 to develop. Medical tourism may cause NDM-1 to spread among countries. Medical tourism refers to people who travel to a country to get medical care that is not available or is more expensive in their own country. The three first cases of NDM-1 infection in the United States were identified in June 2010 in Americans who had recently sought medical care in India. Vacation and business travel have also played a role in introducing NDM-1 bacteria into countries outside of the Indian subcontinent. Cases have now been detected in many countries, including Great Britain, Canada, Sweden, Australia, Japan, and the United States. The number of cases is growing, and the concern is that these highly resistant bacteria could replace more antibiotic-susceptible strains. If this happens, many of the antibiotics that have been developed over the last 80 years will be useless. There are few new ways to kill bacteria that have not already been discovered, and it is feared that infections will return us to the days before antibiotics existed. Currently, NDM-1 bacteria are found mostly in health-care facilities, where antibiotics are used frequently. Therefore, these strains have also acquired resistance genes against other classes of antibiotics. These bacteria are true superbugs resistant to virtually all commonly used antibiotics.

NDM-1 and other resistant bacteria spread from person to person through contact with contaminated hands or items. Good hand hygiene is critical in hospitals to prevent the spread of bacteria and viruses. This includes washing hands with plain soap and water (antibacterial soap causes more resistance) or disinfecting hands with alcohol-based sanitizer.

Most NDM-1 strains must be treated with an older antibiotic called colistin, which had fallen out of use because it can be toxic to kidneys. Some strains may be treatable with the antibiotic aztreonam, or a newer one, tigecycline (Tygacil).

Although NDM-1 has gotten a lot of attention, other CREs with different enzymes have been identified and have spread. This includes the CRE Klebsiella pneumoniae species, also called KPC.

Medically Reviewed by a Doctor on 9/23/2016

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