05/22/2012 05:08 pm ET

Scientists Sequence Genomes Of 12 Antibiotic-Resistant Staphylococcus Aureus Strains

Scientists have gained new clues into what makes certain strains of Staphylococcus aureus so resistant to antibiotics.

Researchers from Massachusetts Eye and Ear have sequenced the genomes of all 12 Staph. aureus strains that are resistant to the antibiotic vancomycin, which is considered the "antibiotic of last resort." The sequencing showed that antibiotic resistance emerged independently in each strain, by picking up some genetic material originating from another vancomycin-resistant bacteria.

The finding, published in the journal mBio could lead to more hope for a viable treatment for these antibiotic-resistant Staph strains, researchers said.

There have been at least 12 cases of Staph. aureus that were resistant to vancomycin since 2002, when the first case appeared in Michigan, researchers said. A pattern has emerged with these cases -- most were in the feet and limbs of people with diabetes, and all of them were infected with both MRSA and Enteroccocus (a kind of bacteria known to be resistant to vancomycin).

The researchers, in conjunction with scientists at MIT, Harvard, the University of Maryland, the University of Rochester and the Wellcome Trust Sanger Center, looked at the genome sequences of all the MRSA strains and found just how MRSA was able to pick up the drug-resistant features from the Enteroccocus bacteria

"What we found was that this group of MRSA has properties that appear to make it more social, so they can live with other bacteria like Enterococcus. This would allow those MRSA to more easily pick up new resistances," study researcher Veronica Kos, Ph.D., of Massachusetts Eye and Ear, said in a statement. "The good news is that some of these properties weaken the strain's ability to colonize, and may be limiting their spread."