Doxy-PEP linked to increased proportion of tetracycline resistance genes in the gut

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Use of doxycycline post-exposure prophylaxis (doxy-PEP) over 6 months was associated with an increase in the proportion and expression of tetracycline antimicrobial resistance genes (ARGs), researchers reported yesterday in Nature Medicine.

In the study, a team led by scientists at the University of California-San Francisco (UCSF) conducted metagenomic DNA sequencing on rectal swabs collected from participants in the DoxyPEP trial, which found that a one-time dose of doxycycline within 72 hours of unprotected sex reduced the incidence of chlamydia, syphilis, and gonorrhea by 88%, 87%, and 55%, respectively. 

Doxy-PEP is now recommended by the Centers for Disease Control and Prevention for populations at high-risk for sexually transmitted infections (STIs), but concerns remain that routine use of doxycycline could promote resistance and negatively impact the gut microbiome.

Dose-dependent increases in tetracycline ARGs

Analysis of rectal swabs collected from 100 trial participants who received doxy-PEP and 50 who received placebo at enrollment and at 6 months found that the proportional mass of tetracycline ARGs increased in the doxy-PEP users and that exposure to a higher number of doxycycline doses correlated with proportional enrichment of tetracycline ARGs. But doxy-PEP did not appear to have an impact on the overall composition of bacterial communities in the gut microbiome.

"While we found no major changes to the community of gut bacteria in doxy-PEP users, we saw that doxy-PEP users over time had increasing amounts of tetracycline resistance genes present in their gut," first author Victoria T. Chu, MD, MPH, an assistant professor of pediatrics at UCSF, said in a university press release. "It also appeared to be dose dependent, meaning the more doxy-PEP they used, the larger the increase was."

The authors add that more research is needed to figure out the clinical implications of their findings, including population-based surveillance to monitor for the emergence of tetracycline resistance. But for now, they say, doxy-PEP remains an important tool for reducing STIs.

"Right now, it looks like the pros outweigh the cons," senior author Chaz Langelier, MD, PhD, said. "Especially given the dramatic rise in STIs, in particular syphilis, over the past decade." 

US markers show more COVID decline, with RSV rise in the southeast

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COVID-19 activity declined last week, with wastewater levels—still highest in the West—now at moderate levels, the US Centers for Disease Control and Prevention (CDC) said today in its latest respiratory virus updates.

COVID test
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Emergency department (ED) and hospitalizations for COVID continue to trend downward, as is test positivity, which is now at 9.2% nationally. ED visits are highest for infants and older adults, and hospitalization rates are highest in seniors. 

Deaths from COVID remain stable, making up about 2% of all US deaths.

Though respiratory syncytial virus (RSV) and flu levels remain low, detections are starting to rise in in the southeast, including in Florida and especially in young children. The CDC reported one more pediatric flu death for the 2023-2024 season, first reported in October 2023, raising the total to 201.

Rising XEC variant levels, but vaccine should still protect

Levels of the dominant KP.3.1.1 SARS-CoV-2 variant continue to rise and are at 58.7%, but in its latest projections, the CDC said the proportion of XEC viruses rose from 2.5% to 6% over the last 2 weeks. It notes that XEC is a recombinant of two JN.1 lineages, and because updated vaccines include a JN.1 lineage virus, they are still expected to provide protection.

So far, the CDC hasn’t noted any XEC impacts on tests, treatments, or symptoms.

 

Ghana reports first mpox case of the year

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Ghana yesterday reported its first mpox case of the year, putting the number of African nations reporting cases to 16, officials from the Africa Centres for Disease Control and Prevention (Africa CDC) said yesterday at a briefing.

mpox virus
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In a statement, the Ghana Health Service said the patient is a young boy from the Western North region who presented with rash, fever, and general body pain. The boy is in stable condition and has been discharged. Health officials are monitoring 25 of the patient’s contacts.

So far, the clade of the virus isn’t known. The country reported eight cases in 2023.

At yesterday’s briefing, Jean Kaseya, MD, MPH, Africa CDC’s director-general, said African countries are still reporting about 2,500 mpox cases each week, though nearly 95% are reported from the Democratic Republic of the Congo (DRC) and Burundi.

In the DRC, the number of cases in Kinshasa are increasing, with one more zone reporting a clade 1b case. The country’s capital is experiencing circulation of both the 1a and 1b clades, with 616 cases, 171 of the confirmed, reported so far.

Kaseya said the mpox vaccination campaign in the DRC is expected to begin tomorrow. Immunization has already launched in Rwanda, and Nigeria is expected to begin giving doses on October 8.

WHO approves first mpox test for emergency use

In other developments, the World Health Organization (WHO) yesterday announced that it has listed the first in vitro mpox test for emergency use. The Alinity mpox test, made by Abbott, is a real-time polymerase chain reaction (PCR) test that can detect clade 1 and 2 mpox virus from lesion swabs.

In a statement, Yukiko Nakatani, MD, PhD, WHO assistant director-general for access to medicines and health products, said, the emergency listing will expand testing availability in affected countries. “Increasing access to quality-assured medical products is central to our efforts in assisting countries to contain the spread of the virus and protect their people, especially in underserved regions.”

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