Chlamydia detection and (maybe) protection.

Chlamydia detection and (maybe) protection

Even its victims may never have heard of it, but Chlamydia trachomatis is the most common sexually transmitted disease agent in the United States. It is also one of the most damaging. The severity of the problem has prompted guidelines for its detection, published in the April 4 JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION, as well as investigations into possible defenses against infection. A report at the recent meeting of the American Society of Microbiologists (ASM) confirms that, in the laboratory, an ingredient in most spermicides prevents chlamydial infection of cells.

The problem with detecting chlamydia is that it is often painless: Asymptomatic in up to 70 percent of the women it infects, it can cause infertility before infection is discovered. "Ideally, you'd like to do universal screening," says researcher H. Hunter Handsfield of the Seattle-King County Department of Public Health, who helped formulate the detection guidelines. But until recently, the only dependable test for chlamydia was expensive, difficult and largely unavailable outside of major medical centers. New immunologic tests that detect the Chlamydia trachomatis bacteria in genital secretions (SN:5/m/83, p.296) are better suited to clinic use, but the cost of the tests is still a stumbling block -- especially, Handsfield and his colleagues note, "in public clinics that serve the populations at highest risk."

In a study of 1,059 women at two family-planning clinics, the researchers found that five characteristics could identify women likely to be infected with chlamydia. The characteristics: no more than 24 years old; having had a new sex partner within the preceding two months; having a purulent cervical discharge; bleeding during parts of the vaginal exam; and using a nonbarrier method of contraception, or no contraception at all. Testing any woman with two or more of these risk factors, they say, would have caught 90 percent of the chlamydial infections at the clinics while reducing the number of women tested by 35 percent.

"What we've shown is if you narrow the net any more than that, you're going to miss a lot of cases," says Handsfield. "Chlamydia infections cross social lines, and a lot of people who don't appear to be at risk...really are."

Chlamydial infection can be effectively treated with antibiotics. But protected by the dificulty of detection, the bacteria have apparently spread at increasing rates over the last decade, according to the Centers for Disease Control in Atlanta; there are now more than 4.5 million new cases of chlamydia each year. The bacteria cause urethritis and other infections in men, whose infection can also be asymptomatic. In women, chlamydia-caused pelvic inflammatory disease can scar fallopian tubes and result in infertility or ectopic pregnancy. Babies born to infected women can develop eye infections and pneumonia.

But some good news: At the recent ASM meeting came confirmation of last year's reports that nonoxynol-9, the active ingredient in most spermicides and in a commercially available contraceptive sponge, has an anti-chlamydial effect in mouse cells in vitro. Researcher P. Blakeney Wyrick of the University of North Carolina at Chapel Hill adds a word of warning to her team's results: If an infected woman uses spermicide shortly before a test for chlamydia. The lack of bacteria in the vaginal canal could lead to a false negative diagnosis.

According to Michael Rosenberg at Family Health International in Research Triangle Park, N.C., early clinical trials are bearing out in vitro research. In women at high risk of infection, he told SCIENCE NEWS, "75 percent of infections, roughly, are prevented by use of the [contraceptive] sponge."