Faced with an alarming spike in syphilis cases, a group of American doctors recently deployed an experimental strategy: asking high-risk patients to take a single pill of a common antibiotic after unprotected sex in an attempt to prevent infection.
San Francisco has become the first U.S. public health authority to issue official guidelines recommending the strategy following the release of two studies showing that doxycycline can slash rate of transmission of the life-threatening disease.
In July, a US study found that taking a single dose of doxycycline within 72 hours of having sex without using a condom reduced the risk of contracting syphilis, chlamydia and gonorrhea by more than 60% in women. people at high risk of contracting sexually transmitted infections. .
This week, a French study evaluating the use of doxycycline and the meningococcal B vaccine to prevent bacterial STIs, both in combination and separately, reported similar results. The trials raised hopes that antibiotics could become a powerful tool in the fight against disease.
“This is a major step forward in the fight against STIs,” said Yazdan Yazdanpanah, director of the French agency ANRS, which funded the study.
He said the positive trial results should lead to changes in global health recommendations to prevent syphilis, chlamydia and gonorrhea.
Physicians working in sexual health said the rollout of doxycycline was needed because of soaring rates of infections transmitted during sex, prompting US officials to warn of a ” sexual health crisis.
The number of syphilis cases in the United States jumped by more than a quarter last year to 171,000, the highest level in more than 70 years, according to the Centers for Disease Control and Prevention.
But the strategy has raised concerns among some experts, who argue that prescribing doxycycline to prevent bacterial STIs could build resistance to an antibiotic also used to prevent malaria and treat other types of infections.
“Having more options to prevent bacterial STIs among high-risk groups is certainly needed and the study data to prevent syphilis and chlamydia is quite compelling,” said Professor Cindy Liu, chief medical officer at the Antibiotic Resistance Action Center at George Washington University. health school.
“But we need to address the concern that this could trigger an increase in doxycycline-resistant MRSA and compromise the usefulness of the antibiotic,” she said, referring to the infection caused by the staph bacteria. “I think we need more data on this, as well as on the evolution of antibiotic-resistant bacterial STIs.”
Liu said San Francisco authorities’ advice to doctors on doxycycline should place more emphasis on the need for patients to be regularly tested for STIs. The study showed that doxycycline was less effective in preventing gonorrhea, which is on the verge of becoming incurable and can increase the risk of contracting HIV.
Gonorrhea, which causes pain and inflammation, has accumulated resistance to seven antibiotics since treatments became widely available in the 1930s. One of the only treatments is an injectable antibiotic called ceftriaxone.
Some experts also worry that using doxycycline to prevent STIs could compromise the use of condoms, which most doctors believe should remain the primary tool for controlling the spread of sexual diseases.
But others say condom use has fallen sharply among high-risk groups, such as men who have sex with men. This is mainly due to the roll-out of PrEP, a once-a-day pill that protects people against HIV infection. This underscores that new tools are urgently needed to halt the spread of STIs, they say.
“People are already using off-label doxycycline – it’s not just being used in these studies, mainly because some patients really need this intervention,” said Troy Grennan, associate professor in the Division of Infectious Diseases at the Institute. University of British Columbia.
He said it was important to continue studying antimicrobial resistance and to send a message that doxycycline should be a targeted intervention for a small number of people. “It’s not a one-size-fits-all STI prevention strategy for everyone,” said Grennan, who has prescribed doxycycline to some high-risk patients.
Researchers have been studying the effect of doxycycline on STIs for several years, but it was the preliminary results of a US study presented in July, involving just over 500 people in high-risk groups, that guest San Francisco public health authorities will issue new guidelines.
The treatment was 88% effective in preventing chlamydia infection in HIV-negative people and 87% effective for syphilis, although its ability to stop gonorrhea was a more modest 55%, according to the study, which did not has not yet been peer reviewed. .
The trial found that a fifth of people diagnosed with gonorrhea were resistant to doxycycline and this increased over the course of the study. There was no evidence of resistance in syphilis or chlamydia.
Annie Luetkemeyer, director of medicine and infectious diseases at the University of California, San Francisco and principal investigator of the study, said more surveillance data from communities where doxycycline was prescribed was needed to determine whether the strategy would increase antibiotic resistance.
“We are reassessing the impact. . . on control bacteria like Staph aureus, commensal Neisseria (found in the throat) and bacteria in the gut,” she said.
The CDC said it was “excited” by the early results of the UCSF study, which was funded by the National Institutes for Health. But Leandro Mena, director of the CDC’s division of STD prevention, said the agency wants to review the full data and consider the issue of antimicrobial resistance before giving official guidance to doctors.
Mena said the agency was also encouraged by a recent study which suggested that a vaccine targeting meningitis had shown promise in reducing the risk of gonorrhea infections by up to 40%. Even a partially effective vaccine could have a significant effect on reducing transmission rates, he said.
“If we could have a vaccine that could effectively reduce the risk of getting these infections. You know that would be the Holy Grail,” added Mena.