Research highlights advantages and dangers of doxy-PEP for STI prevention

Taking a dose of the oral antibiotic doxycycline after a high-risk sexual encounter has dramatically lowered the incidence of sexually transmitted infections (STIs) in locations the place the technique is being tried.

Regardless of its effectiveness, the brand new technique, often called doxy-PEP, might include dangers, particularly with power use. Consultants fear in regards to the influence on the group of intestine micro organism, also called the microbiome, and the potential that the antibiotic will give rise to resistant strains of micro organism. 

Now, utilizing metagenomic sequencing to see the influence of doxycycline on the intestine microbiome of those that took it regularly for six months, UC San Francisco researchers have discovered each reassurance and potential trigger for concern. 

Doxy-PEP didn’t have a lot influence on the general composition of bacterial communities in gastrointestinal tracts. However scientists famous indicators of resistance constructing in opposition to tetracycline, the category of antibiotic that doxycycline belongs to, which might make it much less efficient. 

The examine seems Oct. 3 within the journal Nature Drugs. 

Whereas doxy-PEP didn’t seem to have world impacts on the intestine microbiome, it did have impacts on the antimicrobial resistance of intestine micro organism, each by way of the proportion of tetracycline class resistance genes and the quantity that have been turned on, or expressed.”

Chaz Langelier, Affiliate Professor, Drugs, Division of Infectious Illnesses, College of California – San Francisco

San Francisco’s high-profile STI prevention function 

Doxy-PEP is brief for doxycycline post-exposure prophylaxis, and it includes taking two 100-milligram drugs inside 72 hours of condomless intercourse.

Prompted by early promising medical trial outcomes, San Francisco grew to become the primary metropolis within the nation in October of 2022 to suggest doxy-PEP to homosexual and bisexual males and transgender ladies with a historical past of getting unprotected encounters with a number of companions.

In March of 2024, the San Francisco Division of Public Well being launched outcomes exhibiting that after a few 12 months, the method halved the incidence of chlamydia and early syphilis. In June, the U.S. Facilities for Illness Management and Prevention (CDC) issued tips recommending doxy-PEP for these teams. It was the primary new STI prevention software to be adopted in a long time. 

However the widespread use of antibiotics raises considerations about resistance and the potential dangerous influence on intestine well being, particularly the steadiness of micro organism and different microbes. Disruption can result in diarrhea, nausea, fever and abdominal pain; and till now, there had been very restricted analysis into these unwanted effects. 

Working with the Chan Zuckerberg Biohub and scientists in Washington and Georgia, UCSF researchers studied members from the current doxy-PEP medical trial in San Francisco and Seattle, led by Annie Luetkemeyer, MD, a professor of drugs within the Division of Infectious Illnesses at UCSF. 

The examine included 100 people who used doxy-PEP and 50 people who obtained standard-of-care and didn’t use doxy-PEP. Researchers analyzed rectal swabs collected at enrollment and after six months to review the presence of DNA and RNA from intestine micro organism and their antibiotic resistance genes. 

“Whereas we discovered no main adjustments to the group of intestine micro organism in doxy-PEP customers, we noticed that doxy-PEP customers over time had growing quantities of tetracycline resistance genes current of their intestine,” stated Victoria T. Chu, MD, MPH, an assistant professor of pediatrics within the Division of International Well being and Infectious Illnesses at UCSF and a primary writer of the examine. “It additionally seemed to be dose dependent, which means the extra doxy-PEP they used, the bigger the rise was.” 

Extra analysis is required to find out which intestine micro organism are turning on these tetracycline-resistant genes to know whether or not this may result in extra doxycycline-resistant infections amongst each people taking doxy-PEP and within the larger group.

“Proper now, it seems like the professionals outweigh the cons,” Langelier stated. “Particularly given the dramatic rise in STIs, specifically syphilis, over the previous decade.”