New superbug genes sure to spread, US expert says

A little loop of genes that give bacteria the power to resist virtually all known antibiotics is spreading quickly and likely to cause doctors headaches for years to come, an expert predicted on Wednesday.

They come on the equivalent of a genetic memory stick - a string of genes called a transmissible genetic element.

Bacteria, unlike higher forms of life, can swap these gene strings with other species and often do so with wild abandon.  This one is called New Delhi metallobeta-lactamase 1 or NDM-1 for short and Dr Robert Moellering of Harvard Medical School and Beth Israel Deaconess Medical Centre in Boston predicts it will cause more trouble in the coming years.

"What makes this enzyme so frightening is not only its intrinsic ability to destroy most known beta-lactam antibiotics but also the company it keeps,'' Moellering wrote in a commentary in the New England Journal of Medicine.

First described in 2008, NDM-1 has been found in a wide variety of bacterial types, including the Enterobacteriaceae family, klebsiella and Escherichia coli, all of which are common and cause a range of infections.

British researchers reported in August infections involving NDM-1 had been found in patients in Bangladesh, India, Pakistan and Britain.

"In addition, isolates of Enterobacteriaceae-containing NDM-1 have now been characterized in the United States, Israel, Turkey, China, India, Australia, France, Japan, Kenya, Singapore, Taiwan, and the Nordic countries," Moellering wrote.

Antibiotic-resistant bacteria are nothing new -- virtually all strains of the common Staphylococcus bacteria are now resistant to penicillin. Almost as soon as penicillin was introduced in the 1940s, bacteria began to develop resistance to its effects, prompting researchers to develop many new generations of antibiotics.

But their overuse and misuse have helped fuel the rise of drug-resistant "superbugs." The US Centres for Disease Control and Prevention says most infections that people get while in the hospital resist at least one antibiotic.

For example, half of all Staphylococcus aureus infections in the United States are resistant to penicillin, methicillin, tetracycline and erythromycin. Methicillin-resistant staph aureus or MRSA killed an estimated 19,000 people in the United States alone in 2005.

NDM-1 resists many different types of antibiotic. In at least one case, the only drug that affected it was colistin, a toxic older antibiotic.

"Thus far, the majority of isolates in countries throughout the world can be traced to subjects who have traveled to India to visit family or have received medical care there," Moellering wrote.

"However, the ability of this genetic element to spread rapidly among Enterobacteriaceae means that there will almost certainly be numerous secondary cases throughout the world that are unrelated to travel to the Indian subcontinent."

Experts have been warning for years that poor hospital practices and the overuse of antibiotics spread dangerous bacteria, but practices are changing only slowly.

"The fact that there is widespread nonprescription use of antibiotics in India, a country in which some areas have less than ideal sanitation and a high prevalence of diarrheal disease and crowding, sets the ideal stage for the development of such resistance," Moellering wrote.