Health experts are warning that a new bug which is resistant to antibiotics
has been brought into the UK by patients treated abroad.
The new strains of bacteria, called Enterobacteriaceae, have been identified in UK hospital patients, "a significant proportion of whom had received medical treatment abroad", according to the Health Protection Agency (HPA).
The HPA said that one strain - called NDM-1 (New Delhi Metallo-1) - is "swiftly emerging".
A total of 22 bacteria with the NDM-1 enzyme have been identified from 19 patients at 17 hospitals.
There has been one instance of possible transmission between two patients.
"Critically, at least nine out of 19 affected patients have had recent hospitalisation in India or Pakistan," the HPA said.
One patient received blood treatment in India while two had undergone cosmetic surgery in India.
Others had received renal or liver transplantation in Pakistan.
The HPA said NDM-1 had been repeatedly imported to the UK from the Indian subcontinent, "though there may now also be UK circulation since some affected patients have no immediately identifiable overseas links."
In a statement, it added: "The HPA has been warning for some time of the risk from infections which are more difficult to treat due to antibiotic resistance. The recent emergence of a new group of enzymes (carbapenemases) carried by some bacteria is of concern because these enzymes prevent carbapenem antibiotics from working effectively, making the bacteria resistant to treatment."