Chlamydia's Toxin-Producing Gene Identified

A team of US and Canadian researchers have identified a toxin-producing gene in Chlamydia trachomatis, a bacterium that is a leading cause of sexually transmitted disease. The discovery could lead to new strategies for detecting, treating and possibly preventing chlamydia infection, according to findings published in the Proceedings of the National Academy of Sciences (11.20.01; 98: 13984-13989).

Chlamydia infection often produces a chronic inflammatory reaction. Since the 1940s, scientists had suspected that the bacterium might cause this inflammation by producing some sort of toxin. "The presence of a 'toxin-like' effect had long been suspected but never shown," explained Dr. Robert Belland, the study's lead author and researcher at the National Institutes of Health. Belland and his colleagues identified the toxin-producing gene by comparing two strains of C. trachomatis and studying cells infected by the bacteria. They believe that delivery of the toxin into host cells occurs very early in chlamydia infection and plays a major role in the cell damage caused by the bacterium. Their discovery would not have been possible, Belland said, without the previous sequencing of the genome of C. trachomatis and related bacteria. "Availability of genomic sequence information for a number of these organisms allowed for a comparative genomic approach to identification of the toxin gene," he explained.

The toxin produced by chlamydia, the investigators found, is very similar to a poison released by Clostridium difficile, a bacterium that infects the large intestine. Although the toxin's specific role is unclear at this point, the discovery opens the door to the development of new approaches to chlamydia prevention and treatment, such as the design of vaccines and drug treatments that target the toxin, Belland said. "The toxin may also be an important target in the design of new diagnostic tests for the presence of the organism," he added. Chlamydia infects an estimated 3 million people in the United States each year. Women with untreated chlamydia infection can develop pelvic inflammatory disease, infertility and other problems, and also face an increased risk of HIV infection.

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