HOW BACTERIA DETECT ANTIBIOTICSAn antibiotic kills bacteria by punching holes in its cell wall.But many opportunistic bacteria, such as those that cause lungdisease in people with cystic fibrosis, protect themselvesagainst penicillin and other beta-lactam antibiotics by makingbeta-lactamase, a destructive enzyme. Researchers writing intoday's edition of Science present an initial understanding ofthe means by which the bacteria detects the antibiotic in thefirst place.

This could lead to a more efficient screening of new antibiotics,said Staffan Normack, one of the authors and chairman of themolecular biology department at Washington University in StLouis.

To turn on the gene for the destructive enzyme, most bacteriamust be exposed to the antibiotic. An exception is a bacteriawith a certain mutation in the Amp-D gene, which constantlyproduces the enzyme. Researchers found that in the Amp-Dmutant bacteria there is less cross-linking between theglycopeptide chains of the cell wall. Normack said this impliesthat the bacteria detects the antibiotic by way of the changes itcauses in cell wall structure.

The researchers are now searching for substances that willblock this cell-wall detection, thus preventing bacteria frombecoming resistant to antibiotics. -- Rachel Nowak


Measuring the level of two "surrogate markers" in the blood ofpatients infected with the AIDS virus could serve as a way toevaluate the effectiveness of anti-viral medications.Researchers at the University of California, San Francisco,report in the Jan. 12 issue of the British Medical Journal thatthis could be a useful means of measuring the effectiveness ofdrugs in infected individuals even before the humanimmunodeficiency virus (HIV) develops into AIDS.

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