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Drug resistance

Drug resistance a mutated gene acquired from a harmless microbe can make a pathogenic bacterium drug resistant, claims a study at the Laboratory of Microbiology, Rockefeller University, New York.

A team of scientists led by Alexander Tomasz, showed that bacteria fortify their cell walls using a protein produced by a gene called mecA, and become resistant to antibiotics from the b-lactam group that includes penicillin. These antibiotics work by inhibiting proteins needed to construct cell walls. The research finding could lead to ways to prevent the spread of drug resistance.

Tomasz used the bacterium Staphylococcus aureus to demonstrate his point. This bacterium is a major cause of infection of surgical wounds in hospitals. In the absence of mecA, the bacterium remains susceptible to drugs but if it has the gene, it builds a cell wall even in the presence of antibiotics.

It has been known for some time now that this gene has been acquired from another bacterium called S sciuri, which lives on the skin of domestic and wild animals such as mice and squirrels. S sciuri is fully sensitive to b-lactam antibiotics even though it has the mecA gene. If this gene gets mutated, S sciuri acquires drug resistance. When mutated mecA was introduced in S aureus, it also became resistant to b-lactam antibiotics. What was significant was that the presence of mecA in S aureus did not result in a cell wall similar to that of S sciuri . "Even though the two bacteria use different molecules to make their cell walls, we found that the mecA protein can use what is available to build the cell wall,' says Tomasz. The research appears in a recent issue of Journal of Bacteriology (Vol 187, No 19).

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