Taking a dose of the oral antibiotic doxycycline after a high-risk sexual encounter has dramatically reduced the incidence of sexually transmitted infections (STIs) in places where the strategy is being tried. Despite its effectiveness, the new strategy, known as doxy-PEP, may come with risks, especially with chronic use. Experts worry about the impact on the community of gut bacteria, also known as the microbiome , and the potential that the antibiotic will give rise to resistant strains of bacteria.
Now, using metagenomic sequencing to see the impact of doxycycline on the gut microbiome of those who took it frequently for six months, UC San Francisco researchers have found both reassurance and possible cause for concern. Doxy-PEP did not have much impact on the overall composition of bacterial communities in gastrointestinal tracts. But scientists noted signs of resistance building against tetracycline, the class of antibiotic that doxycycline belongs to, which could make it less effective.
The study appears Oct. 3 in the journal Nature Medicine . While doxy-PEP did not appear to have global impacts on the gut microbiome, it did have impacts on the antimicrobial resistance of gut bacteria, both in terms of the proportion of tetracycline class resistance genes and the amount that were turned on, or expressed.
" Chaz Langelier, Associate Professor, Medicine, Division of Infectious Diseases, University of California - San Francisco San Francisco's high-profile STI prevention ro.