Staph Bacteria Are Active Gene Swappers

W A S H I N G T O N, July 9 -- The bacteria that cause serious and sometimesfatal staph infections are able to swap genes with relatives inorder to adapt to new environments and cause even greater medicalmischief, a study shows.

Researchers using a new technology to analyze the gene structureof bacteria found that Staphylococcus aureus can easily exchangegenes with other bacteria strains and can acquire resistance toantibiotics within a very short time.

Staphylococcus aureus, or staph, is an extremely troublesomebacterium that causes a variety of illnesses. It is a major causeof hospital-acquired infection. Staph causes such things as thescalded skin disease that strikes infants, toxic shock syndrome andsystemic blood poisoning called sepsis.

Drug-Resistant Staph

Antibiotics once controlled the bacteria, but strains of staphare now resistant to the drugs.

"This is the first time we've been able to do such an extensivegenetic comparison of these strains of Staphylococcus aureus,"said Dr. James M. Musser, senior author a study appearing Tuesdayin the Proceedings of the National Academy of Sciences.

Musser is head of a bacterial research lab at the NationalInstitute of Allergy and Infectious Disease's Rocky MountainLaboratories in Hamilton, Mont. NIAID is one of the NationalInstitutes of Health.

In the study, Musser and his colleagues analyzed the genes of 36of the most troublesome strains of staph and concluded thatvirtually any of the bacteria's 2,817 strains could acquire thegenes to become resistant to antibiotics.

"This is occurring at a far more greater frequency than weanticipated," said Musser. "The drug-resistant strains can becreated many times. It is not a single strain that is created onceand then spreads."

Instead, he said the genetic combination that providesresistance can arise independently in many different places, manydifferent times.

Such an easy evolution of drug resistance "has sent a wave ofterror through people responsible for public health," said Dr.Abigail A. Salyers, a microbe researcher at the University ofIllinois, Urbana. "They know this organism will become a majorpathogen if antibiotics no longer work."