Syphilis, a sexually transmitted disease that is on the rise in the United States, may be developing resistance to one of the antibiotics used to treat it, according to a federal study released on Thursday.
Health officials in San Francisco documented eight cases in 2002 and 2003 in which single oral doses of azithromycin apparently failed to cure the infection, according to a report published by the Centers for Disease Control and Prevention.
All of the patients were gay males and five were infected with HIV, the virus that causes AIDS. They were subsequently treated successfully with either doxycycline or penicillin, the antibiotic preferred by the CDC for syphilis treatment.
The San Francisco City Clinic has since dropped use of azithromycin in most cases of primary, secondary or early-latent syphilis, said Dr. Samuel Mitchell, a CDC epidemiologist and one of the authors of the study.
Untreated syphilis can cause arthritis, heart disease, insanity and death as well as miscarriages, stillbirths and severe infections in newborn babies. It also has been shown to help spread HIV.
The apparent failure of azithromycin is a blow to infectious disease specialists, who had hoped that a single 1-gram or 2-gram dose would provide a more convenient and better treatment for many syphilis infections.
On the rise in the U.S.
Several studies have shown that the treatment was effective in patients who were not infected with HIV. It is also much easier to administer than benzathine penicillin, which is usually injected into patients.
“The downside of azithromycin becoming less useful is that it will probably limit our ability to do in-the-field or prophylactic treatment,” said Mitchell, who urged doctors still prescribing the drug for syphilis to closely follow patients.
The study came just three days after the Atlanta-based CDC reported that the nation’s syphilis rate likely had risen for the third consecutive year, mostly due to a rise in infections among gay and bisexual men.
In 2003 there were 7,082 confirmed cases of primary and secondary syphilis, the initial stages of the disease, compared with 6,862 cases in 2002, according to preliminary CDC data. The rate of syphilis rose to 2.5 cases per 100,000 people from 2.4 cases per 100,000 during the period.
The CDC estimated that 60 percent of the cases last year occurred among men who had sex with men, compared with 5 percent in 1999.
