A microbe in battle gear

Carries an arsenal of 45 drug-resistant genes

Published: Wednesday 15 February 2006

a pathogen that is a common cause of hospital infections may well be able to defend itself against attack by any antibiotic, according to a study conducted by researchers from the Structural and Genomic Information Laboratory at France's National Center for Scientific Research.

The bacterium, Acinetobacter baumannii, was fully susceptible to antibiotics about three decades ago. But over the years, it has acquired drug-resistant genes from other bacterial pathogens like Pseudomonas, Salmonella and Escherichia.

For the study, the research team compared the genomes of two A baumannii strains, one fully susceptible to antibiotics and one highly resistant. The resistant bacterium, present in an epidemic form in several French healthcare facilities, is associated with a mortality of 26 per cent of infected patients.

The group found that the resistant strain has 45 genes coding for drug resistance -- the highest found in any bacterial pathogen. Seventeen of the 45 genes have been identified for the first time. Usually, foreign genes occur in genetic material outside the pathogen's chromosome. But in A baumannii, they were present in the chromosome. "It is like the A baumannii genome is 'anticipating' any antibacterial challenge by setting up some kind of easily accessible 'shelves' to store the antibacterial resistances genes," says Jean-Michel Claverie, who led the study.

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