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Complete Sequence Of Staph Bacterium Genome Described

The complete genetic sequence of Staphylococcus aureus, a bacterium that is a major source of infection in human beings and one of the most resistant organisms in hospital-acquired infections, is described in this week's issue of The Lancet.

This important event in the history of infectious disease not only reveals for the first time how S. aureus causes such devastating damage to human beings, but also points to important new targets for drug development.

Keiichi Hiramatsu and colleagues from the Department of Bacteriology, Juntendo University, Tokyo, Japan, sequenced two strains of S. aureus. One was a meticillin-resistant form of the bacterium (MRSA): the other was a vancomycin-resistant variant.

Their findings fall into four key clinically important areas:

* First, the complex complement of genes in S. aureus has been partly acquired from many different organisms, ranging from other bacteria to Homo sapiens. This remarkable characteristic, combined with repeated duplication of genes coding for "superantigens," has produced a bacterium with immense infective power.

* Second, critical antibiotic-resistance genes exist as "mobile genetic elements" or "plasmids." In an accompanying commentary (p. 1218), Dlawer Ala'Aldeen and Hajo Grundmann point out that these mobile pieces of genetic material have the worrying potential to spread between strains of S. aureus as well as across species boundaries.

* Third, Hiramatsu and colleagues have discovered five new classes of genes -- "pathogenicity islands" -- that produce potentially lethal toxins responsible for, among other conditions, toxic-shock syndrome. Finally, these investigators have found 70 new virulence-factor candidates that could become targets for new drug development.

Hiramatsu and colleagues also speculate that the S. aureus genome sequence, especially the superantigens it encodes, "might shed light on research into Kawasaki's disease and other inflammatory diseases of unknown cause."

Ala'Aldeen and Grundmann conclude that these findings are "a major contribution to the understanding of ... this important pathogen."

[Contact: Prof. Keiichi Hiramatsu, Dr. Dlawer Ala'Aldeen]

20-Apr-2001

 

 

 

 

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