In August of 2010 The Lancet published a study (see NDM-1: A New Acronym To Memorize) by Walsh, Toleman, Livermore, et al. chronicling the emergence and spread from the Indian sub-continent of a new enzyme – dubbed NDM-1 (New Delhi metallo-ß-lactamase-1) - that can confer resistance to certain gram negative bacteria like E.coli and Klebsiella against a class of antibiotics called carbapenems.
Carbapenems are newer generation beta-lactam antibiotics (that includes imipenem, meropenem, doripenem, and ertapenem) that are usually reserved as an antibiotic of last resort.
Of particular concern, this enzyme is carried by a plasmid – a snippet of portable DNA - that can be transferred to other types of bacteria (see Study: Adaptation Of Plasmids To New Bacterial Species).
Since then, scattered variants of NDM-1 have begun to emerge; NDM-2, NDM-4, and NDM-5.
Last September, an EID Journal letter called New Delhi Metallo-β-Lactamase 4–producing Escherichia coli in Cameroon, gave a description of the recent rise of these new variants.
Since 2010, 3 NDM-1 point-mutation variants have been described (3–5). The first variant, NDM-2, was identified from an Acinetobacter baumannii isolate collected from a patient transferred from a hospital in Egypt to Germany (4).
Subsequently, a clonal dissemination of NDM-2–producing A. baumanni was described in Israel (6). The second variant, NDM-4, which was identified in Escherichia coli from a patient hospitalized in India, possessed a higher carbapenemase activity compared with NDM-1 (5).
The most recent variant, NDM-5, was identified in E. coli from a patient who had a history of hospitalization in India (3).
While detections of these NDM variants remain rare, today Hong Kong announced their first detection of NDM-4 in a patient recently returned from India.
Tuesday, January 15, 2013
Issued at HKT 20:06
The Public Health Laboratory Services Branch (PHLSB) of the Centre for Health Protection (CHP) of the Department of Health confirmed today (January 15) a case of New Delhi metallo-β-lactamase-4 (NDM-4) Carbapenemase-producing Enterobacteriaceae in a 73-year-old man.
The patient with chronic illness travelled to New Delhi, India, on December 26, 2012. He developed symptoms of fever, shortness of breath and productive cough on December 28 and therefore sought medical attention at a local hospital without hospitalisation.
Upon arrival in Hong Kong, he sought medical consultation from another private doctor on January 3, 2013 and was admitted to Princess Margaret Hospital (PMH) on January 8. The clinical diagnosis was bronchitis and he was discharged on January 10. His condition remains stable.
The patient's rectal swab grew NDM-4 Carbapenemase-producing Enterobacteriaceae, as confirmed by the PHLSB.
His family contacts are asymptomatic. The CHP's investigation is under way.
This is the 18th detected case of NDM Carbapenemase-producing Enterobacteriaceae in Hong Kong and is the first NDM-4 case reported to the CHP.
"NDM-4 is a variant of NDM found in India," a CHP spokesperson said.
Like with MRSA, carriage of NDM bacteria does not necessarily mean infection, but asymptomatic carriers can still spread it to contacts and to the environment.
The rise of antibiotic resistance - including these emerging NDM enzymes - has long been linked to the overuse and misuse of antibiotics. A practice that is still widespread in many parts of the world, but is particularly rampant on the Indian sub-continent.
Citing a lack of doctors and low family incomes, the Indian government (see India: Still Looking For A Policy On Antibiotics) has been slow to stop the sale of antibiotics to the public without a doctor’s prescription.
For more on the importance of proper antibiotic stewardship, you may wish to revisit these earlier blogs.
And Maryn’s SUPERBUG Blog, part of Wired Science Blogs, continues to provide the best day-to-day coverage of these issues.