Doctors Find Cystic Fibrosis Carriers Have Greater Resistance to Typhoid

Cystic fibrosis may be one of the most common hereditary diseases because carriers of the faulty gene have an enhanced natural resistance to typhoid, U.S. doctors report in Nature. The finding could explain why the defective gene is passed on to subsequent generations.

Cystic fibrosis occurs when a child has two defective copies of the gene, one from each parent, that encodes a protein known as cystic fibrosis transmembrane conductance regulator (CFTR). The researchers found that normal CFTR protein is a receptor for Salmonella typhimurium, a gastrointestinal bacterium that causes typhoid fever. But when CFTR is mutated or missing, the bacterium does not bind and the disease is averted. Having one copy of the defective gene does not cause cystic fibrosis, but it does provide protection against typhoid.

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Compiled by Times medical writer Thomas H. Maugh II