NDM-1 refers to a gene’s protein product that some bacteria make. A bacterial strain that carries NDM-1 will be resistant to even some of the strongest antibiotics.

Few current antibiotics can combat bacteria that have the NDM-1 gene, making it potentially dangerous.

NDM-1 stands for New Delhi metallo-ß-lactamase-1. A medical team first isolated the gene in a Swedish patient of Indian origin who traveled to India in 2008.

What led to the emergence of NDM-1 in India is not clear.

This superbug is widespread in India, and, by 2015, researchers and medical experts detected it in more than 70 countries worldwide.

In this article, we explore the nature and possible dangers of bacteria with the NDM-1 gene.

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An NDM-1 superbug is resistant to almost all antibiotics.

The NDM-1 protein product itself does not cause disease, but it has the potential to change the characteristics of bacteria.

The gene makes bacteria resistant to antibiotics. In this way, it can lead to a range of conditions, such as a urinary tract, bloodstream, or wound infections and pneumonia.

Carbapenems are among the most powerful antibiotics. Healthcare professionals use them as a last resort for many bacterial infections, such as those that E. coli and Klebsiella pneumoniae cause.

The NDM-1 gene allows the bacterium to produce an enzyme that neutralizes the activity of these antibiotics.

The Centers for Disease Control and Prevention (CDC) have classified NDM-1 and another similar protein called KPC as emerging issues in the field of infectious diseases.

A bacterium carrying the NDM-1 gene is considered a very powerful superbug.

The NDM-1 protein is different from the protein product that characterizes methicillin-resistant Staphylococcus aureus (MRSA), another superbug. MRSA are a Gram-positive bacteria, while the bacteria that carry NDM-1 are Gram-negative, a different classification of bacteria.

The World Health Organization (WHO) is concerned that NDM-1 could see in “the doomsday scenario of a world without antibiotics.”

Before the discovery of antibiotics in 1928, many people died because of infections that are now avoidable.

NDM-1 raises fears that diseases in the future will not respond to antibiotics. If NDM-1 crosses over into other bacteria, secondary diseases will emerge, causing a health crisis as they spread around the world.

The WHO suggest that a woman who is pregnant, for example, could develop a kidney infection that transfers into the bloodstream with a strain containing NDM-1. In this case, no treatment options would be available that are safe for a woman during pregnancy.

The NDM-1 gene causes bacteria to produce an enzyme called a carbapenemase. Carbapenemase renders many preferred types of antibiotic ineffective, including carbapenems.

Carbapenem antibiotics are extremely powerful drugs that can counter the activity of highly resistant bacteria for which other antibiotics have not been effective. Even
carbepenems are ineffective in cases of NDM-1.

A bacterium with a plasmid containing the NDM-1 protein product has the potential to be resistant to many current antibiotics, as well as newer antibiotics that could become available in the near future.

Research is on-going into possible solutions to NDM-1.

The plasmid containing the genetic code for NDM-1 can move from one strain of bacteria to another through a process known as horizontal gene transfer (HGT).

If NDM-1 jumps to a bacterium that is already antibiotic-resistant, dangerous infections could emerge. These would spread rapidly between people and might not be treatable.

In 2010, researchers became aware that some strains of bacteria, such as E. coli and Klebsiella pneumoniae, carry the gene that produces NDM-1. They have since learned that horizontal gene transfer (HGT) between bacteria that express KPC and NDM-1 is possible.

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Scientists expect that secondary NDM-1 viruses will spread without a person having come into contact with India.

The people who discovered the NDM-1 protein named it after New Delhi, the Indian capital. The gene for this is widespread in bacteria found in India and Pakistan, especially in hospitals.

It initially occurred mainly in India and Pakistan, and specifically in New Delhi, where the climate encourages its persistence year round. Since then, it has occurred in drinking water and the holy rivers of India, such as the Ganges.

Bacteria expressing NDM-1 have surfaced in countries around the world, including the United States, Japan, Australia, and the United Kingdom, in patients who spent time in India, traveled through it, or have family members there.

Some people carried the infection home after traveling to India or Pakistan for cosmetic surgery, as this type of treatment is less expensive in Asia.

However, the ability of the NDM-1 gene to spread to other kinds of bacteria means that scientists are expecting to see numerous secondary cases in other countries that do not have links to time spent in India.

At the moment, the only way to combat the spread of bacteria expressing NDM-1 is through the following measures:

  • surveillance
  • quickly identifying and isolating patients with the bacteria
  • disinfecting hospital equipment
  • following hand-hygiene procedures in hospitals

So far, patients with NDM-1-related infections have been treated on a case-by-case basis, with a combination of medications, but few effective and no oral treatments are available for many of the infections caused by NDM-1.

Some strains of bacteria are totally resistant to virtually all kinds of antibiotic.

In 2014, Morad Hasssani of the Albert Einstein College of Medicine in New York, NY, called on “all stakeholders in this public health crisis” to do their part, including an increase in research budgets, increased responsibility and commitment from pharmaceutical companies, and new approaches from medical scientists.

Since 2001, the WHO has urged health professionals to reduce the use of antibiotics and bring down the risk of resistance in bacterial diseases. This also involves keeping carbapenem use to a minimum.

The Center for Disease Dynamics, Economics and Policy note that “antibiotic resistance is a direct result of antibiotic use.” Europe, Canada, and the United States have reduced their use of antibiotics in recent years, but usage is still increasing in India, Sub-Saharan Africa, Latin America, and Australia.

Even as medical use of antibiotics reduces, concerns remain about the agricultural use of antibiotics, as these might enter the human system in food and leak into the environment.

The NDM-1-expressing superbug is a potentially dangerous bacterium that could become resistant to many types of antibiotic, spreading quickly.

NDM-1 refers to a gene product present in some bacteria that counters antibiotics. If bacteria expressing this gene start to spread, treatment using currently available measure will not be possible.

The first signs of the bug occurred in India and have spread through travel. Overuse of antibiotics increasing the risk of NDM-1 expression and transferring to other bacteria through a process called HGT.

Surveillance, the isolation of patients with the infection, and good hospital hygiene are the only protective measures available at present.


Am I at risk of catching a superbug?


Risks associated with coming into contact with a superbug typically include admission to a hospital with poor antibiotic stewardship practices, travel to a high-risk location, and having received many different antibiotics.

While not always avoidable, these risk factors can increase the likelihood of coming in contact with a superbug.

You can reduce your risk by taking antibiotics precisely as recommended by a doctor and obtaining preventative care in an outpatient setting when possible.

Daniel Murrell, MD Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.
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