Questions & Answers on NDM-1
What is NDM-1?
How does it spread?
Where has it spread so far?
Why is it a major healthcare risk?
How is NDM-1 different from other types of carbapenemases?
What can be done to prevent it?
Can it be treated?
What is NDM-1 ?
- NDM-1 is a Metallo Beta-Lactamase essentially found in Enterobacteriaceae (principally E. coli and K. pneumoniae).
- NDM-1 stands for New Delhi Metallo-beta-lactamase-1, since it was first identified in a Swedish patient of Indian origin, who had been admitted to hospital in New Delhi, India in 2008.
- The NDM-1 gene produces an enzyme which makes bacteria resistant to almost all beta-lactams including carbapenems (imipenem, meropenem, ertapenem, doripenem). Carbapenems are powerful, broad-spectrum antibiotics, which are often considered to be the last line of defence against multi-resistant strains of bacteria, such as E. coli and K. pneumoniae.
How does it spread ?
- The gene for NDM-1 is found on plasmids (DNA strands), which can easily spread from one strain of bacteria to another, particularly in patients receiving antibiotic treatment.
Where has it spread so far ?
- So far, the large majority of cases have been reported in India, Pakistan and Bangladesh.
- However, since mid-August 2010, additional cases have been reported worldwide except for Central and South America: Australia, Austria, Belgium, Canada, Denmark, China, France, Germany, Hong Kong, Italy, Japan, Kenya the Netherlands, Norway, Singapore, South Korea, Sweden, the Sultanate of Oman, Taiwan, the United Kingdom and the United States.
- Several cases have also revealed the origin of patients or hospitalization stays as being in Balkan countries (Bosnia, Kosovo, Montenegro and Serbia). This is the case for patients from Austria, Belgium, Denmark and Germany.
- Cases found outside of the Indian sub-continent have been linked to patients recently receiving medical care or cosmetic surgery in that region.
Why is it a major healthcare risk ?
Lack of effective antibiotics
- NDM-1 bacteria are resistant to most antibiotics (fluroquinolones, aminoglycosides and beta-lactams), except tigecycline and colistin.
- However, several cases of colistin-resistant K. pneumoniae (5 in US, 1 in Hungary, 2 in Greece and 1 in Korea all in 2010) have been reported, meaning such very serious infections are now only treatable by a single remaining drug: tigecycline.
Bogdanovich T. et al. Clin Infect Dis. 2011 ;53 :373-376
http://cid.oxfordjournals.org/content/53/4/373.full.pdf+html
- Furthermore, in August 2011, the first case of a patient infected with E. coli carrying NDM-1 who developed tigecycline resistance was reported (J. Antimicrob. Chemother. (2011) doi: 10.1093/jac/dkr337). http://jac.oxfordjournals.org/content/early/2011/08/16/jac.dkr337.extract
Colistin continued to work, and the patient recovered. But now tigecycline resistance will pose an additional threat.
- Currently, there are few new antibiotics against Gram-negative bacteria in development and none that are effective against NDM-1.
High risk of rapid NDM-1 transmission
- The NDM-1 type of plasmidic resistance means it can transfer easily to other bacteria and has been identified in several different and unrelated bacterial strains. Transmission can be accelerated by “medical tourism”, and by the high level of population exchanges between India and Pakistan and other countries around the globe. NDM-1 is found in E. coli - the most frequent cause of urinary tract infections, which is commonly found in the community. The fact that E. coli is a typical community-acquired bacteria may also accelerate the spread of NDM-1 resistant strains, since the resistance is not limited to the healthcare setting. The spread of this new resistance gene is strongly facilitated by the following conditions:
- low level of hygiene
- overpopulation
- hot, humid climate
- widespread over-the-counter use of antibiotics.
How is NDM-1 different from other types of carbapenemases?
- There is no major difference from other carbapenemases (same shortage of antibiotics), except that NDM-1 occurs in E. coli, therefore presenting a greater risk factor since it could potentially migrate in the community.
What can be done to prevent it?
- Standard infection control / hygiene measures applied in the case of nosocomial or community-acquired infections can be applied to reduce the transmission of NDM-1.
Healthcare setting
Key measures for prevention are:
- increased screening (particularly all patients transferred from overseas hospitals)
- isolation of carriers and reinforced hygiene measures
- prudent use of antibiotics
- monitoring and surveillance of antibiotic resistance
Individual precautions
Actions which can help to reduce the transmission of E. coli and therefore NDM-1 include:
- frequent, thorough handwashing
- cleanliness when preparing and consuming food
- reinforcing precautions when in contact with persons with a urinary tract infection/diarrhea
- reinforcing contact precautions if you yourself have a urinary tract infection/diarrhea
Can it be treated?
- It is difficult to treat patients infected by bacteria which harbour this new resistance mechanism, since NDM-1 is highly resistant to almost all antibiotics, including carbapenems. Currently, it appears that two antibiotics (tigecycline and colistin) are still effective, but resistance can occur (see paragraph on “Lack of Effective Antibiotics” above). The severity of infections involving NDM-1 can vary from mild to fatal.
Where can I learn more?
 Carbapenem resistance and NDM-1 -Q&A from the UK Health
Protection Agency
> Read more
 CDC MMWR (Morbidity and Mortality Weekly Report) June 25, 2010 /
Vol.59 / No.24 / Page 250
> Read more
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