April 02, 2008

Resistant super bugs defeat doctors

Drug-resistant super bugs have foreclosed treatment options for critically ill patients and forced doctors to prescribe medicines banned 20 years ago because of severe side effects.

But some of these microbes have quickly developed resistance to even these older drugs, says a new study.

"Doctors in many countries have gone back to using old antibiotics abandoned 20 years ago because their toxic side effects were so frequent and so bad," said Matthew Falagas of Tufts University, Massachusetts.

One such super bug is Acinetobacter, which has challenged doctors worldwide by becoming resistant even to these older and more dangerous medicines.

Colistin, an antibiotic discovered 60 years ago, was recently salvaged to treat patients with Acinetobacter infections, said Falagas, who presented the study at the Society for General Microbiology's meeting in Edinburgh.

"It was successful for a while, but now it occasionally fails due to recent extensive use that has caused the bacteria to become resistant to all available antibiotics," he said.

Greek researchers have shown that Acinetobacter is a more serious threat than previously thought - it doesn't just cause severe infections, it kills many more patients than doctors had realised. Acinetobacter can cause pneumonia, skin and wound infections and in some cases meningitis.

The scientists have also identified a whole range of drug resistant strategies being used by the bacteria.

These include the production of compounds that can inactivate the drug treatments, cell pumps that can bail out the drug molecules from inside bacterial cells making them ineffective, and mutating the drug target sites.

"There have already been severe problems with critically ill patients due to Acinetobacter baumannii infections in various countries," Falagas informed.

"In some cases we have simply run out of treatments and we could be facing a pandemic with important public health implications."

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