A Genomic Perspective on the Near-term Impact of Doxycycline Post-exposure Prophylaxis on Neisseria gonorrhoeae Antimicrobial Resistance

Effects of doxycycline post-exposure prophylaxis for prevention of sexually transmitted infections on gonorrhoea prevalence and antimicrobial resistance among men who have sex with men in the USA: a modelling study

BACKGROUND

Doxycycline post-exposure prophylaxis (PEP) has been shown to be efficacious for the prevention of bacterial sexually transmitted infections, but resistance implications for Neisseria gonorrhoeae remain unknown. We aimed to use a mathematical model to investigate the anticipated impact of doxycycline PEP on the burden of gonorrhoea and antimicrobial resistance dynamics in men who have sex with men (MSM) in the USA.

METHODS

Using a deterministic compartmental model, characterising gonorrhoea transmission in a US MSM population comprising three sexual activity groups defined by annual partner turnover rates, we introduced doxycycline PEP at various uptake levels (10-90%) among those with high sexual activity. Infections were stratified by symptom status and resistance profile (ie, susceptible, ceftriaxone-resistant, tetracycline-resistant, or dual-resistant), with ceftriaxone the treatment for active infection. As resistance to tetracycline, not doxycycline, is monitored and reported nationally, we used this as a proxy for doxycycline PEP resistance. We compared the 20-year prevalence, incidence rates, and cumulative incidence of gonococcal infection, resistance dynamics (time to 5% prevalence of ceftriaxone resistance, 5% prevalence of dual resistance, and 84% prevalence of tetracycline resistance), and antibiotic consumption with baseline (ie, no doxycycline PEP).

FINDINGS

Uptake of doxycycline PEP resulted in substantial reductions in the prevalence and incidence of gonorrhoea, but accelerated the spread of tetracycline resistance. The maximum reduction in prevalence over 20 years compared with no uptake ranged from 40·3% (IQR 15·3-83·4) with 10% doxycycline PEP uptake to 77·4% (68·4-84·9) with 90% uptake. Similarly, the maximum reduction in the incidence rate ranged from 38·6% (14·1-83·6) with 10% uptake to 77·6% (68·1-84·7) with 90% uptake. Cumulative gonococcal infections were reduced by a median of 14·5% (IQR 8·4-21·6) with 10% uptake and up to 46·2% (26·5-59·9) with 90% uptake after 5 years, and by 6·5% (3·4-13·0) with 10% uptake and 8·7% (4·3-36·2) with 90% uptake by 20 years. In almost all scenarios explored, doxycycline PEP lost clinical effectiveness (defined as 84% prevalence of tetracycline resistance) within the 20-year period, but its lifespan ranged from a median of 12·1 years (IQR 9·9-15·7) with 10% uptake to 1·6 years (1·3-1·9) with 90% uptake. Doxycycline PEP implementation had minimal impact on extending the clinical lifespan of ceftriaxone monotherapy (5·0 years [IQR 4·0-6·2]), with the median time to 5% prevalence of resistance ranging from 4·8 years (3·9-6·0) for 90% uptake to 5·0 years (4·1-6·2) for 10% uptake. Similarly, the median time to 5% prevalence of dual resistance to ceftriaxone and tetracycline ranged from 4·8 years (3·9-6·0) for 90% uptake to 5·8 years (4·8-7·4) for 10% uptake. Median decrease in ceftriaxone consumption for high doxycycline PEP uptake levels compared with baseline ranged from 41·7% (27·0-54·3) for 50% uptake to 50·2% (29·3-62·7) for 90% uptake at 5 years, but dropped to 11·8% (6·9-32·0) for 50% uptake and 12·1% (7·0-41·6) for 90% uptake after 20 years.

INTERPRETATION

Notwithstanding the clear benefits of doxycycline PEP for other sexually transmitted infections, for N gonorrhoeae, model findings suggest that doxycycline PEP is an effective but impermanent solution for reducing infection burden, given eventual selection for resistant strains. This finding presents a challenge for policy makers considering strategies for doxycycline PEP implementation and oversight: the need to balance the clear, short-term clinical benefits with the risk of harm via antimicrobial resistance.

FUNDING

US Centers for Disease Control and Prevention, National Institute of Allergy and Infectious Diseases.

Emergence of Extensively Drug-Resistant Neisseria gonorrhoeae, France, 2023

Since 2022, Europe has had 4 cases of extensively drug-resistant Neisseria gonorrhoeae, sequence type 16406, that is resistant to ceftriaxone and highly resistant to azithromycin. We report 2 new cases from France in 2023 involving strains genetically related to the 4 cases from Europe as well as isolates from Cambodia.

Doxycycline post-exposure prophylaxis among men who have sex with men and transgender women in Belgium: awareness, use and antimicrobial resistance concerns in a cross-sectional online survey

OBJECTIVES

We aimed to assess the awareness, willingness to use and use of doxycycline post-exposure prophylaxis (doxyPEP) among men who have sex with men (MSM) and transgender women (TGW) in Belgium. Additionally, we aimed to identify factors associated with doxyPEP use and concerns regarding antimicrobial resistance (AMR).

METHODS

Cross-sectional online survey among MSM and TGW in Belgium in April 2024. Participants were recruited through sexual networking applications and social media of community-based organisations. Numerical variables were compared with Wilcoxon rank-sum test and categorical variables with χ2 or Fisher's exact tests. Factors associated with doxyPEP use were assessed using logistic regression. Willingness to use doxyPEP and concerns about side effects/AMR were assessed before and after presenting a brief paragraph on the potential effects of doxyPEP on AMR.

RESULTS

875 individuals initiated the survey. Almost all identified as men (860/875, 98.3%) with a median age of 40 years (IQR 32-48), 40.4% (n=352/875) had heard of doxyPEP and 9.4% (n=82/875) had used it, among whom the majority used it within the previous 6 months (70/81, 86.4%). In multivariable logistic regression, doxyPEP use was associated with reporting ≥1 sexually transmitted infection (STI) in the previous 12 months, engagement in chemsex, HIV status and pre-exposure prophylaxis use, and education level.About 80% of the participants initially reported being willing to use doxyPEP, and about 50% reported being concerned about side effects. After reading about the potential effects of doxyPEP on AMR, willingness to use decreased to 60% and concerns of side effects/AMR increased to around 70%.

CONCLUSIONS

Approximately 1 in 10 MSM in Belgium reported using doxyPEP. A recent history of STIs and STI risk factors were positively associated with doxyPEP use. Importantly, concerns about AMR and side effect influenced willingness to use doxyPEP. If doxyPEP is introduced, informing patients about doxyPEP benefits and risks is crucial to enable informed decision-making.

IUSTI Europe position statement on use of DoxyPEP: June 2024

This position statement is aimed at front-line clinical practitioners and public health authorities in WHO European Region providing services for people wishing to reduce their risk of acquiring sexually transmitted infections (STIs), including HIV.

Assessing thresholds of resistance prevalence at which empiric treatment of gonorrhea should change among men who have sex with men in the US: A cost-effectiveness analysis

BACKGROUND

Since common diagnostic tests for gonorrhea do not provide information about susceptibility to antibiotics, treatment of gonorrhea remains empiric. Antibiotics used for empiric therapy are usually changed once resistance prevalence exceeds a certain threshold (e.g., 5%). A low switch threshold is intended to increase the probability that an infection is successfully treated with the first-line antibiotic, but it could also increase the pace at which recommendations are switched to newer antibiotics. Little is known about the impact of changing the switch threshold on the incidence of gonorrhea, the rate of treatment failure, and the overall cost and quality-adjusted life-years (QALYs) associated with gonorrhea.

METHODS AND FINDINGS

We developed a transmission model of gonococcal infection with multiple resistant strains to project gonorrhea-associated costs and loss in QALYs under different switch thresholds among men who have sex with men (MSM) in the United States. We accounted for the costs and disutilities associated with symptoms, diagnosis, treatment, and sequelae, and combined costs and QALYs in a measure of net health benefit (NHB). Our results suggest that under a scenario where 3 antibiotics are available over the next 50 years (2 suitable for the first-line therapy of gonorrhea and 1 suitable only for the retreatment of resistant infections), changing the switch threshold between 1% and 10% does not meaningfully impact the annual number of gonorrhea cases, total costs, or total QALY losses associated with gonorrhea. However, if a new antibiotic is to become available in the future, choosing a lower switch threshold could improve the population NHB. If in addition, drug-susceptibility testing (DST) is available to inform retreatment regimens after unsuccessful first-line therapy, setting the switch threshold at 1% to 2% is expected to maximize the population NHB. A limitation of our study is that our analysis only focuses on the MSM population and does not consider the influence of interventions such as vaccine and common use of rapid drugs susceptibility tests to inform first-line therapy.

CONCLUSIONS

Changing the switch threshold for first-line antibiotics may not substantially change the health and financial outcomes associated with gonorrhea. However, the switch threshold could be reduced when newer antibiotics are expected to become available soon or when in addition to future novel antibiotics, DST is also available to inform retreatment regimens.

Position statement of the German STI Society on the prophylactic use of doxycycline to prevent STIs (Doxy-PEP, Doxy-PrEP)

Over the past two decades, there has been a rise in the incidence of syphilis, particularly among men who have sex with men (MSM). This has sparked interest in studying the prophylactic use of doxycycline to prevent syphilis and other sexually transmitted infections (STIs), commonly referred to as Doxycycline Pre- or Post-Exposure Prophylaxis (Doxy-PrEP, Doxy-PEP). At the same time, demand from potential users for this preventive measure is increasing. Several randomized controlled trials have demonstrated that the prophylactic use of doxycycline in MSM and trans women using HIV pre-exposure prophylaxis (HIV-PrEP) or living with an HIV infection effectively reduces the risk of syphilis and chlamydia infections. At present, however, unresolved questions remain, particularly regarding implications of a broad implementation of prophylactic doxycycline to prevent STIs on tetracycline and other antimicrobial resistance in bacterial STIs, non-STI-related bacterial pathogens, and the microbiome. In response to the increasing demand and the challenge of balancing effectiveness, safety, and the risk of promoting antibiotic resistance, the German STI Society (DSTIG) has issued a position statement, providing specific recommendations regarding potential indications, criteria, and occasions for the use of doxycycline in STI prevention. These recommendations are based on current evidence and expert opinion.

The Management of Gonorrhea in the Era of Emerging Antimicrobial Resistance: What Primary Care Clinicians Should Know

Gonorrhea rates continue to rise in the United States and Neisseria gonorrhoeae's propensity to develop resistance to all therapies used for treatment has complicated the management of gonorrhea. Ceftriaxone is the only remaining highly effective recommended regimen for gonococcal treatment and few new anti-gonococcal antimicrobials are being developed. The 2021 CDC STI Treatment Guidelines increased the dose of ceftriaxone to 500 mg (1 g if ≥ 150 kg) for uncomplicated infections. It is recommended that all clinicians should be aware of antimicrobial resistant gonorrhea and be able to appropriately manage any suspected gonorrhea treatment failure case.

Stellungnahme der Deutschen STI-Gesellschaft zur antibiotischen STI-Prophylaxe mit Doxycyclin (Doxy-PEP, Doxy-PrEP): Position Statement of the German STI Society on the Prophylactic Use of Doxycycline to Prevent STIs (Doxy-PEP, Doxy-PrEP)

Seit etwa zwei Jahrzehnten ist eine Zunahme der Syphilisinzidenz zu beobachten, insbesondere unter Männern, die Sex mit Männern haben (MSM). Diese Entwicklung hat zu einem wachsenden Interesse an Studien zur prophylaktischen Anwendung des Antibiotikums Doxycyclin zur Vermeidung von Syphilisinfektionen und anderen sexuell übertragbaren Infektionen (STI), international meist als Doxycyclin‐Prä‐ beziehungsweise Post‐Expositionsprophylaxe (Doxy‐PrEP, Doxy‐PEP) bezeichnet, geführt. Zugleich steigt die Nachfrage seitens potenzieller Nutzer nach dieser präventiven Maßnahme.

Mehrere randomisierte kontrollierte Studien haben gezeigt, dass die prophylaktische Anwendung von Doxycyclin bei MSM und Trans‐Frauen mit HIV‐PrEP‐Gebrauch oder bekannter HIV‐Infektion das Risiko einer Syphilis‐ und Chlamydien‐Infektion wirksam reduziert. Zum gegenwärtigen Zeitpunkt bestehen jedoch noch offene Fragen, insbesondere hinsichtlich der möglichen Auswirkungen einer breiten Anwendung der antibiotischen STI‐Prophylaxe mit Doxycyclin auf Tetrazyklin‐ und andere antimikrobielle Resistenzen bei bakteriellen STI, anderen bakteriellen Pathogenen und Bakterien des Mikrobioms.

Angesichts der steigenden Nachfrage und der Herausforderung, eine Abwägung zwischen Wirksamkeit, Sicherheit und dem Risiko der Förderung von Antibiotikaresistenzen vorzunehmen, hat die Deutsche STI‐Gesellschaft (DSTIG) die vorliegende Stellungnahme erarbeitet. Diese enthält spezifische Empfehlungen zu potenziellen Indikationen, Kriterien und Anlässen für den Einsatz von Doxycyclin zur Prävention von STI. Die Empfehlungen basieren auf aktuellen Studienergebnissen und der Meinung von Fachpersonen.

Filling in the Gaps: Updates on Doxycycline Prophylaxis for Bacterial Sexually Transmitted Infections

Over the past two decades, cases of sexually transmitted infections (STIs) due to syphilis, gonorrhea, and chlamydia have been rising in the United States, disproportionately among gay, bisexual, and other men who have sex with men (MSM), as well as racial and ethnic minorities of all genders. In this review, we address updates about the evidence on doxycycline post-exposure prophylaxis (doxy-PEP) for prevention of bacterial STIs, including efficacy, safety, antimicrobial resistance (AMR), acceptability, modeling population impact, and evolving guidelines for use. Equitable implementation of doxy-PEP will require evaluation of who is offered and initiates it, understanding patterns of use and longer-term STI incidence and AMR, provider training, and tailored community education.

STI pathogens in the oropharynx: update on screening and treatment

PURPOSE OF REVIEW

The rise in antimicrobial resistance in several STI pathogens such as Neisseria gonorrhoeae has become a public health threat as only one first-line treatment remains. Reducing screening interval for gonorrhoea and chlamydia in high-prevalence populations has been proposed to address antimicrobial stewardship, but this remains controversial. This review aimed to revisit the epidemiology of infections at the oropharynx and review the current screening recommendations and treatment guidelines in different populations.

RECENT FINDINGS

Emerging evidence suggests that the oropharynx is the primary anatomical site for gonorrhoea transmission but maybe not for chlamydia transmission. Most international guidelines recommend 3-monthly oropharyngeal gonorrhoea and chlamydia screening for high-prevalence populations (e.g. men who have sex with men) but not low-prevalence populations (e.g. heterosexuals) given the clinical and public health benefits of screening in low-prevalence populations are still unclear. Doxycycline remains the first-line treatment for oropharyngeal chlamydia in most guidelines. However, some countries have moved from dual therapy (ceftriaxone and azithromycin) to monotherapy (ceftriaxone) for oropharyngeal gonorrhoea treatment to address antimicrobial stewardship.

SUMMARY

The transmission of gonorrhoea and chlamydia is still not fully understood. Further work will be required to evaluate the benefits and harms of reducing screening in high-prevalence populations.