The antibiotic-resistant enzyme, the carbapenemase NDM-1, has been appearing in recent headlines across the globe. For that reason, the Healthy Travel Blog requested some perspective on the situation from Dr. Vanya Gant, a Specialist in Infectious Diseases and Microbiology in London.  Here are his thoughts on the background, risk and future of this “superbug.”  

NDM-1 is one of several enzymes which destroy carbapenem antibiotics such as meropenem, imipenem, doripenem and ertapenem and are therefore called carbapenemases. By breaking down the carbapenem groups of antibiotics, these can no longer be relied on to treat infections. NDM-1 stands for New Delhi metallo-beta-lactamase 1.

The carbapenem group of antibiotics are powerful antibiotics for treating Gram negative bacteria (coliform bacteria such as E.coli and Klebsiella species) which can cause urinary tract infections, and are responsible for a considerable proportion of Hospital Acquired Infections.

The genetic material that leads to the production of the carbapenemase enzyme is found on a small mobile element (referred to as a plasmid – a sort of virus within a bacterium) that can easily pass from one bacterium to another. This ability to transmit from one bacterium to another implies that there is an alarming potential for it to spread among many other bacterial populations.

Q: Is this the first time that a carbapenemase has been described?

No. Other carbapenemases called VIM, KPC and OXA have been identified in Klebsiella species. These have caused problems in Greece, Turkey, USA and Israel.

Q: Where do these come from?

The rise of another antibiotic resistance enzyme, ESBL (extended spectrum β lactamase), which made Gram negative bacteria resistant to the cephalosporins, has led to an increase in the use of the carbapenems. This in turn has provided a selection pressure for carbapenem resistance to emerge, and is yet another example of the remarkable ability of bacteria to adapt and eventually become resistant to new antibiotics. This is made much easier by the existence of these “bacterial viruses” called plasmids, which can transmit easily from bacterium to bacterium.

Q: What is the risk of this enzyme?

It means that a very effective class of antibiotics may no longer be used for treatment of infection.

What’s more, it would appear that the plasmid carrying this resistance also carries resistance to other antibiotics. This means that once predictably powerful and active antibiotics such as the modern penicillins and cephalosporins, and other antibiotic classes such as the quinolones (such as ciprofloxacin), and the aminoglycosides (such as gentamicin – a hospital antibiotic) may not always work.

Q: Can NDM-1 still be treated?

The bacteria carrying the NDM-1 resistance enzyme remain sensitive to individual aminoglycosides and aztreonam, and many, if not most, isolates remained susceptible to colistin and tigecycline. Combinations of antibiotics are used to treat it.

Q: Are there new antibiotics that could help?

While there is large investment in research to find new antibiotics, currently there are no plans to approve or license one that could provide a single solution.

Q: How is it spread?

NDM-1 can spread from person to person in hospitals, hence the importance of environmental cleaning and hygiene as well as individual personal hygiene. In India it has spread outside hospitals through contaminated water in which people bathe, wash clothes and also defecate.

Q: Why is it a problem?

Ultimately, NDM-1 strains could produce dangerous infections that would spread rapidly from person to person and be almost impossible to treat.

Human air travel and migration allow bacteria and their plasmids to be transported rapidly between countries and continents. Much of this dissemination is undetected with resistant clones carried in the normal human flora (in their intestines mostly) and only becoming evident when they are the source of endogenous infections.

NDM-1 is widespread in India and Pakistan and has arrived in several distant countries as a result of global travel. While a particular issue for the UK, medical tourism for procedures such as transplants, pregnancy care and cosmetic surgery, has been a contributing factor for other developed nations.

The potential for wider international spread of NDM-1 plasmids and other similar novel antibiotic resistance genes to become endemic worldwide is clear and frightening.

Q: What can be done to stop it?

Individuals must be aware of the possibility that they may pick these strains up if they receive medical care in India and Pakistan.

It is currently extremely unlikely that they will pick these strains up in other countries — even though they have been found, they continue to be very rare.

It remains axiomatic that the best way to protect oneself against these resistant organisms is to be very aware of one’s own personal hygiene, and to make sure that wherever possible any healthcare received is from accredited units offering the very best levels of infection control and antibiotic stewardship.

Author: Dr. Vanya Gant
Dr. Vanya Gant, PhD, FRCP FRCPath is a specialist in Infectious Diseases and Microbiology.  He is Divisional Clinical Director for Infection at University College London Hospitals Trust in London, England.  In addition to patient care and clinical service redesign, Dr. Gant develops new techniques and materials for combating infection. He has appeared in several Public service and independent programs on matters of infection and microbiology, some of which he co-wrote.  In his free time, he enjoys and plays music, rides fast motorcycles, pilots paragliders, cooks and is an aspiring dance music DJ.