Correspondence in the March edition of The Lancet Infectious Diseases looks at the possible explanations for the detection of NDM-1 carbapenemase (providing super-resistance) in bacteria from patients who had visited the group of countries in southeastern Europe commonly known as The Balkans (including Bosnia, Serbia, Kosovo and Montenegro). The letter is by the same authors that wrote the Lancet Infectious Diseases NDM-1 paper in 2010 and include Dr David Livermore and Dr Neil Woodford (Health Protection Agency, UK) and Professor Timothy Walsh (University of Cardiff, UK).
Letters to The Lancet Infectious Diseases in December 2010 reported cases of patients infected by bacteria with NDM-1 in various countries worldwide. While most had been to the Indian subcontinent (consistent with the paper mentioned above), a small minority from Belgium, Denmark and Germany had not been to the Indian subcontinent but had visited Balkan countries. Struelens and colleagues reported that, among 55 patients with blaNDM-1 positive bacteria and a travel history, 31 had visited the Indian subcontinent and five had visited these Balkan countries. Some of these cases reported by Struelens were the same as those reported directly to The Lancet Infectious Diseases.
The authors offer two explanations for this; the first being that NDM-1 appeared independently in both this region of southeastern Europe and the Indian subcontinent. Alternatively, the NDM-1 enzyme, which was already circulating in India in 2006 (versus the first Balkan-linked case in 2007) could have been imported from the subcontinent to southeastern Europe. They refer to a paper by Ivanoski and colleagues about patients from southeastern Europe travelling to Pakistan for commercial kidney transplants, many with poor outcomes and frequent infection. They say: "At least four of the UK patients with NDM-1-positive bacteria had a history of renal transplant in Pakistan. Medical tourism of this sort could have introduced NDM-1 to the Balkans."
They conclude by saying there are insufficient data to confirm or refute either hypothesis, and more extensive genetic analysis of the flanking genetic sequences around the NDM-1 gene in these samples will be necessary to gain more evidence. They conclude: "If these sequences are different, the Balkan cases likely represent a second (independent) gene escape; if they are identical, then import to the Balkans is the more probable explanation. But this hypothesis cannot be definitively proven without a clear epidemiological trail."
While not part of the Correspondence, the authors additionally suggest that surveillance to determine the extent of carbapenem resistance in Enterobacteriaceae in these countries of southeastern Europe would be an appropriate first step. Microbiologists in these countries should, say the authors, be encouraged to generate data that will lead to fuller understanding of the epidemiology of NDM-1-positive bacteria.
Contact Dr David Livermore via the Health Protection Agency, UK press office. T) +44 (0) 208 327 7097 Kathryn.swan@hpa.org.uk
For full Correspondence, see: http://press.thelancet.com/tlidndm1letter.pdf
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Journal
The Lancet Infectious Diseases