New Delhi Metallo-beta-lactamase (NDM-1) is an enzyme that makes bacteria resistant to a broad range of beta-lactam antibiotics. These include the antibiotics of the carbapenem family, which are a mainstay for the treatment of antibiotic-resistant bacterial infections. The gene for NDM-1 is one member of a large gene family that encodes beta-lactamase enzymes called carbapenemases.
Bacteria that have these genes are often referred to in the news media as "superbugs" because infections caused by them are difficult to treat. Indeed, the United Kingdom's Health Protection Agency has reported that "most isolates with NDM-1 enzyme are resistant to all standard intravenous antibiotics for treatment of severe infections."

NDM-1 was first identified in December 2009 in a patient hospitalised in New Delhi with an infection caused by Klebsiella pneumoniae. It was later detected in bacteria in India, Pakistan, the United Kingdom, the United States, and Canada. The most common bacteria that make this enzyme are Gram negative such as Escherichia coli and Klebsiella pneumoniae, but the gene for NDM-1 can spread from one strain of bacteria to another by horizontal gene transfer.

Enzyme function

Structure of the carbapenem backbone.Carbapenems are a class of beta-lactam antibiotics which are capable of killing most bacteria by inhibiting the synthesis of one of their cell wall layers. The carbapenems were developed to overcome antibiotic resistance mediated by bacterial beta-lactamase enzymes. However, the blaNDM-1 gene produces NDM-1,which is a carbapenemase beta-lactamase - an enzyme that hydrolyzes and inactivates these carbapenem antibiotics.

Origin and spread

The NDM-1 enzyme was named after New Delhi, the capital city of India, as it was first described by Yong et al. in December 2009 in a Swedish national who fell ill with an antibiotic-resistant bacterial infection that he acquired in India. The infection was unsuccessfully treated in a New Delhi hospital and after the patient's repatriation to Sweden, a carbapenem-resistant Klebsiella pneumoniae strain bearing the novel gene was identified. The authors concluded that the new resistance mechanism "clearly arose in India, but there are few data arising from India to suggest how widespread it is." In March 2010 a study in a hospital in Mumbai found that the majority of carbapenem-resistant bacteria isolated from patients carried the blaNDM-1 gene.

In May 2010 a case of infection with E. coli expressing NDM-1 was reported in Coventry in the United Kingdom.Indian responseThe Indian health ministry has disputed the conclusion of the August 2010 Lancet study that the gene originated in India or Pakistan, describing this conclusion as "unfair" and stating that Indian hospitals are perfectly safe for treatment.
Indian politicians have described linking this new drug resistance gene to India as “malicious propaganda” and blamed multinational corporations for what they describe as selective malignancy. A Bharatiya Janata Party politician has instead argued that the journal article is bogus and represented an attempt to scare medical tourists away from India.
The Indian Ministry of Health released a statement "strongly refuting" naming the enzyme "New Delhi". The primary author of the 2010 Lancet study, who is based in the University of Madras, has stated that he does not agree with the part of the article that advises people to avoid elective surgeries in India.

Patient zero

In August 2010, the first reported death due to a bacteria expressing the NDM-1 enzyme was recorded as a Belgian man who had become infected, while being treated in a hospital in Pakistan. He died despite being administered colistin, a powerful antibiotic. A doctor involved in his treatment said, "He was involved in a car accident during a trip to Pakistan. He was hospitalized with a major leg injury and then repatriated to Belgium, but he was already infected".

Read about antibiotic resistance also superbugs and bacteria

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