CDC Clinical Guidelines on the Use of Doxycycline Postexposure Prophylaxis for Bacterial Sexually Transmitted Infection Prevention, United States, 2024

Chronic meningitis: diagnostic and therapeutic challenges

PURPOSE OF REVIEW

We review recent advances in diagnosis and treatment of chronic meningitis, focusing on tuberculous meningitis (TBM), cryptococcal meningitis (CM), syphilitic meningitis, neuroborreliosis, and recurrent chronic meningitis. Noninfectious causes and unique challenges faced in resource-limited settings are also considered.

RECENT FINDINGS

Novel biomarkers are being identified that may be useful for the diagnosis of TBM [i.e. monokine induced by interferon-γ (MIG), plasminogen binding proteins] and syphilitic meningitis (i.e. CXCL13, neurofilament light protein, etc.) but require more validation. Much progress has been made regarding diagnosis and treatment of CM, with a new semiquantitative lateral flow assay showing high diagnostic and prognostic utility and clinical trials demonstrating that regimens of oral lipid nanocrystal formulation and a single dose of liposomal formulation of amphotericin B maintain clinical efficacy with improved side effect profiles. An ongoing clinical trial of ceftriaxone for treatment of syphilitic meningitis and early stage studies of linezolid for TBM treatment may also lead to changes in recommended treatment regimens for these conditions in the near future.

SUMMARY

Diagnosis and management of chronic meningitis remains a significant challenge, and further research is needed to improve our diagnostic and therapeutic armamentariums. However, emergence of potential new biomarkers for diagnosis and disease course is cause for optimism.

Knowledge, Use, and Misuse of Self-Prescribed Doxycycline Postexposure Prophylaxis in a Community-Based Preexposure Prophylaxis Service

ABSTRACT

This study described knowledge and usage of doxycycline postexposure prophylaxis (doxyPEP) among preexposure prophylaxis users. A survey was launched enrolling 703 respondents: 28.2% were aware of doxycycline postexposure prophylaxis, but only 8.8% used it. One quarter discussed it with medical doctors, and only 51.6% used the recommended dosing. Doxycycline postexposure prophylaxis needs to be implemented within appropriate guidelines.

Awareness, Attitudes, and Interest in Doxycycline Postexposure Prophylaxis as Bacterial Prophylaxis Against Sexually Transmitted Infections-New York City Sexual Health Clinics, June to August 2023

BACKGROUND

Increased incidence of bacterial sexually transmitted infections including chlamydia, gonorrhea, and syphilis dictates the need for novel prevention strategies. One such strategy, doxycycline prescribed prophylactically, has proven to be effective at reducing transmission among men who have sex with men and transgender women. We assessed awareness, attitudes, and interest in doxycycline preexposure/postexposure prophylaxis (doxyPrEP/doxyPEP) among New York City sexual health clinic patients, including men who have sex with men, other cisgender men, women, transgender persons, and patients identifying as gender nonconforming or nonbinary.

METHODS

A self-administered survey was completed by 280 patients from 5 New York City sexual health clinics between June and August 2023 that collected information assessing their knowledge, concerns, and willingness to use doxyPrEP and doxyPEP. We used Poisson regression models to examine factors associated with willingness to use doxyPEP.

RESULTS

Of the 280 patients, 73% (205) and 55% (153) reported that they would take doxyPEP and doxyPrEP, respectively, if offered by their provider. Willingness to use doxyPEP was observed across gender groups and significantly associated with history or current use of HIV preexposure prophylaxis (adjusted risk ratio [aRR], 1.17; 95% confidence interval [CI], 1.07-1.27). Compared with non-Hispanic White participants, Hispanic (aRR, 1.27; 95% CI, 1.07-1.52) and non-Hispanic other (Alaskan Native, American Indian, Native Hawaiian, Pacific Islander, multiracial) group (aRR, 1.28; 95% CI, 1.06-1.56) participants were more likely to report willingness to use doxyPEP. Possible antibiotic resistance was of highest concern.

CONCLUSIONS

If offered by a provider, doxyPEP would likely be accepted by patients of all gender groups. Additional research on acceptability in other settings would help guide widespread implementation.

Doxycycline post-exposure prophylaxis as prevention of STIs - the golden bullet?

INTRODUCTION

Doxycycline post-exposure prophylaxis ('doxyPEP') is an emerging strategy to prevent bacterial sexually transmitted infections (STIs). Users take 200 mg of doxycycline up to 72 hours after condomless sex, and data from randomized controlled trials and real-world implementation have shown doxyPEP to be effective in preventing syphilis, chlamydia, and to a lesser extent gonorrhea, in gay, bisexual, and other men-who-have-sex-with-men (GBMSM) and transgender women.

AREAS COVERED

We discuss the potential benefits, risks, and important considerations for doxyPEP implementation, drawing on published literature and our own perspectives.

EXPERT OPINION

Is doxyPEP the golden bullet? DoxyPEP provides significant benefits through STI prevention and holistic improvements in sexual health and wellbeing. Concerns over emergent antimicrobial resistance need to be weighed against STI-related morbidity and contextualized within society's overuse of antibiotics. Inequities in the doxyPEP evidence-base and implementation will undermine its ability to end the syphilis epidemic and reduce chlamydia associated morbidity in cisgender women. Moreover, contexts in which doxyPEP proves effective for gonorrhea prevention initially are unlikely to see a long-lasting impact. Rather than a golden bullet, doxyPEP is a bridge to the next set of STI prevention tools.

Exploring programme implementation of a US paediatric hospital-based violence intervention programme by injury mechanism

BACKGROUND

Hospital-based violence intervention programmes (HVIPs) support recovery following interpersonal violence, with most patients participating following firearm injuries. There remains insufficient understanding of who HVIPs serve and how programmes are implemented, especially among paediatric patients. We sought to describe the implementation of a paediatric HVIP and examine relationships between HVIP implementation metrics and mechanism of injury (firearm vs non-firearm).

METHODS

We conducted a retrospective cohort study using HVIP records from 2018 to 2023, identifying 2021 patients (8-18 years) treated at our urban paediatric trauma centre in the northeastern USA, 416 of whom enrolled in our HVIP. We conducted bivariate and multivariate regression analyses examining differences in patient-level characteristics and HVIP implementation by injury mechanism.

RESULTS

Most patients (94%) experienced non-firearm injuries. Firearm-injured patients were more likely to enrol in our HVIP (adjusted OR=4.01, 95% CI 2.64 to 6.14) than non-firearm-injured patients, though non-firearm-injured patients represented 85% of HVIP participants. In comparison to non-firearm-injured patients, firearm-injured patients had longer programme duration (adj_B=43.73, 95% CI 4.84 to 82.63 days), more documented encounters (adj_B=16.30, 95%CI 3.44 to 29.16) and more recovery goals (adj_B=3.37, 95%CI 1.21 to 5.52). HVIP goal resolution and graduation rates did not significantly differ by mechanism.

CONCLUSION

Our study identified metrics to describe HVIP implementation among paediatric patients with diverse injury types and documented consistent HVIP engagement, retention and outputs for those with firearm and non-firearm injuries alike. Our work suggests the relevance, and acceptability of HVIPs for paediatric patients with diverse injuries and offers a framework for process measurement in future implementation, outcome and impact evaluations.

Evaluating cross-protection: Meningococcal vaccines show effectiveness in gonorrhoea prevention - A systematic review and meta-analysis

BACKGROUND

Gonorrhoea remains a significant global health concern, with men who have sex with men (MSM) being disproportionately affected. Recent evidence suggests that outer membrane vesicle (OMV) meningococcal vaccines, such as the most widely used 4CMenB vaccine, may provide cross-protection against gonorrhoea.

OBJECTIVES

We aimed to evaluate the effectiveness of OMV vaccines against gonorrhoea through a systematic review and meta-analysis.

METHODS

PubMed, Embase, and CENTRAL were searched from inception to 10 July 2024. Original articles were included if they investigated gonorrhoea incidence among recipients of OMV vaccines. Our primary endpoint was the incidence of gonorrhoea among vaccinated and unvaccinated individuals. The risk of bias was assessed using ROBINS-I, and the RoB-2 tools. A random-effects model with a 95 % confidence interval (CI) was applied to estimate pooled effect sizes. The study was registered on PROSPERO, CRD42024530848.

RESULTS

We identified 12 eligible studies for qualitative analysis. Six retrospective studies and one prospective study were included in the quantitative analysis, of which six investigated the 4CMenB OMV vaccine. The pooled analysis yielded a vaccine effectiveness (VE) of 38 % [95 % CI:22 %-50 %; I2 = 55 %]. Including only the 4CMenB vaccine, VE was 41 % (OR = 0.59; 95 % CI:0.46-0.76; I2 = 44 %). Complete vaccination might offer 24 % greater protection compared to partial vaccination (OR = 0.76; 95 % CI:0.31-1.85; I2 = 86 %). VE declined in 2-3 years post-vaccination. Four studies were rated as low risk, four as moderate risk, and four as having serious risk of bias. The certainty of the evidence was graded as moderate. The main limitations include the retrospective nature and the high heterogeneity of the included studies.

CONCLUSIONS

OMV vaccines offer moderate protection against gonorrhoea. 4CMenB OMV vaccine should be prioritised for sexually active individuals over non-OMV alternatives, with emphasis on completing the full vaccination series. Consideration should be given to administering 4CMenB to high-risk MSM groups specifically for gonorrhoea prevention.

Using Structural Equation Modeling to Examine Barriers and Facilitators of HIV Pre-Exposure Prophylaxis Willingness and Length of Use in Men Who Have Sex with Men Who Use Substances in Eight Southern US Cities

Men who have sex with men who use substances (SU-MSM) can benefit from pre-exposure prophylaxis (PrEP) for HIV prevention, especially in Southern US cities where HIV incidence is high; however, uptake remains low. Identifying barriers and facilitators is crucial for developing and implementing strategies to enhance uptake. Few studies of PrEP barriers and facilitators have focused on Southern SU-MSM, and most existing studies have not robustly measured such barriers and facilitators. In this study, 225 SU-MSM were recruited from community STI clinics, syringe services programs, or substance use treatment programs in eight Southern cities. Using structural equation modeling, we examined latent variable constructs of barriers and facilitators (i.e., affordability, burden, risk compensation, side effects, and stigma) and their associations with both willingness to take PrEP and length of PrEP use. Greater concern over affordability was robustly associated with more willingness to take PrEP under a variety of conditions. Risk compensation was associated with greater length of PrEP use, suggesting a major motivator to remain on PrEP was the perceived freedom to forego condoms during sex. Findings advance research on measurement of barriers and facilitators of PrEP willingness and uptake and highlight the importance of addressing affordability in PrEP implementation.

Doxycycline post-exposure prophylaxis: a primer for dermatologists

Doxycycline post-exposure prophylaxis (DoxyPEP) is an effective strategy to reduce bacterial sexually transmitted infections (STIs) in high-risk populations. With its 2024 endorsement by the CDC, DoxyPEP offers timely benefits amid rising STI rates, but its broader adoption raises concerns about antimicrobial resistance and potential side-effects. Dermatologists, with their extensive experience in prescribing doxycycline, are well positioned to educate patients, optimize its safe use and contribute to holistic sexual health prevention strategies.

Terminal complement complexes with or without C9 potentiate antimicrobial activity against Neisseria gonorrhoeae

The complement cascade is a front-line defense against pathogens. Complement activation generates the membrane attack complex (MAC), a 10-11 nm diameter pore formed by complement proteins C5b through C8 and polymerized C9. The MAC embeds within the outer membrane of Gram-negative bacteria and displays bactericidal activity. In the absence of C9, C5b-C8 complexes can form 2-4 nm pores on membranes, but their relevance to microbial control is poorly understood. Deficiencies in terminal complement components uniquely predispose individuals to infections by pathogenic Neisseria, including N. gonorrhoeae (Gc). Increasing antibiotic resistance in Gc makes new therapeutic strategies a priority. Here, we demonstrate that MAC formed by complement activity in human serum disrupts the Gc outer and inner membranes, potentiating the activity of antimicrobials against Gc and re-sensitizing multidrug-resistant Gc to antibiotics. C9-depleted serum also exerts bactericidal activity against Gc and, unlike other Gram-negative bacteria, disrupts both the outer and inner membranes. C5b-C8 complex formation potentiates Gc sensitivity to azithromycin and ceftriaxone, but not lysozyme or nisin. These findings expand our mechanistic understanding of complement lytic activity, suggest a size limitation for terminal complement-mediated enhancement of antimicrobials against Gc, and suggest that complement manipulation can be used to combat drug-resistant gonorrhea.

IMPORTANCE

The complement cascade is a front-line arm of the innate immune system against pathogens. Complement activation results in membrane attack complex (MAC) pores forming on the outer membrane of Gram-negative bacteria, resulting in bacterial death. Individuals who cannot generate MAC are specifically susceptible to infection by pathogenic Neisseria species including N. gonorrhoeae (Gc). High rates of gonorrhea, its complications like infertility, and high-frequency resistance to multiple antibiotics make it important to identify new approaches to combat Gc. Beyond direct anti-Gc activity, we found that the MAC increases the ability of antibiotics and antimicrobial proteins to kill Gc and re-sensitizes multidrug-resistant bacteria to antibiotics. The most terminal component, C9, is needed to potentiate the anti-Gc activity of lysozyme and nisin, but azithromycin and ceftriaxone activity is potentiated regardless of C9. These findings highlight the unique effects of MAC on Gc and suggest novel translational avenues to combat drug-resistant gonorrhea.

Antiretroviral Postexposure Prophylaxis After Sexual, Injection Drug Use, or Other Nonoccupational Exposure to HIV - CDC Recommendations, United States, 2025

Nonoccupational postexposure prophylaxis (nPEP) for HIV is recommended when a nonoccupational (e.g., sexual, needle, or other) exposure to nonintact skin or mucous membranes that presents a substantial risk for HIV transmission has occurred, and the source has HIV without sustained viral suppression or their viral suppression information is not known. A rapid HIV test (also referred to as point-of-care) or laboratory-based antigen/antibody combination HIV test is recommended before nPEP initiation. Health care professionals should ensure the first dose of nPEP is provided as soon as possible, and ideally within 24 hours, but no later than 72 hours after exposure. The initial nPEP dose should not be delayed due to pending results of any laboratory-based testing, and the recommended length of nPEP course is 28 days. The recommendations in these guidelines update the 2016 nPEP guidelines (CDC. Updated guidelines for antiretroviral postexposure prophylaxis after sexual, injection drug use, or other nonoccupational exposure to HIV - United States, 2016. Atlanta, GA: US Department of Health and Human Services, CDC; 2017). These 2025 nPEP guidelines update recommendations and considerations for use of HIV nPEP in the United States to include newer antiretroviral (ARV) agents, updated nPEP indication considerations, and emerging nPEP implementation strategies. The guidelines also include considerations for testing and nPEP regimens for persons exposed who have received long-acting injectable ARVs in the past. Lastly, testing recommendations for persons who experienced sexual assault were updated to align with the most recent CDC sexually transmitted infection treatment guidelines. These guidelines are divided into two sections: Recommendations and CDC Guidance. The preferred regimens for most adults and adolescents are now bictegravir/emtricitabine/tenofovir alafenamide or dolutegravir plus (tenofovir alafenamide or tenofovir disoproxil fumarate) plus (emtricitabine or lamivudine). However, the regimen can be tailored to the clinical circumstances. Medical follow-up for persons prescribed nPEP also should be tailored to the clinical situation; recommended follow-up includes a visit at 24 hours (remote or in person) with a medical provider, and clinical follow-up 4-6 weeks and 12 weeks after exposure for laboratory testing. Persons initiating nPEP should be informed that pre-exposure prophylaxis for HIV (PrEP) can reduce their risk for acquiring HIV if they will have repeat or continuing exposure to HIV after the end of the nPEP course. Health care professionals should offer PrEP options to persons with ongoing indications for PrEP and create an nPEP-to-PrEP transition plan for persons who accept PrEP.

Factors Influencing Oral Pre-, Post-, and Doxycycline Post-Exposure Prophylaxis Uptake Among Substance-Using Men Who Have Sex with Men in the Rural Southern US

Substance-using men who have sex with men (MSM), especially those in rural areas, face a heightened risk of HIV and sexually transmitted infections (STIs). Despite increased risk, uptake of HIV pre-exposure prophylaxis (PrEP), HIV post-exposure prophylaxis (PEP), and doxycycline post-exposure prophylaxis (Doxy-PEP) remains low among rural MSM. The multi-domain factors influencing past-year use of oral PrEP, PEP, and Doxy-PEP among substance-using MSM in the rural southern US remain unknown. A cross-sectional study of rural substance-using MSM (n = 345) in the Southern US was conducted from February 29 to March 23, 2024. Three series of bivariate and multivariate logistic regression analyses were conducted. Past-year PrEP use was significantly associated with HIV-negative status (adjusted odds ratio [aOR] = 2.55, 95% confidence interval [CI]: 1.12-5.80, p = 0.025), past-year STI diagnosis (aOR = 2.23, 95% CI: 1.19-4.15, p = 0.012), past-year HIV testing (aOR = 3.40, 95% CI: 1.05-10.9, p = 0.040), and past-year STI testing (aOR = 10.09, 95% CI: 2.25-45.37, p = 0.003). Past-year PEP use was significantly associated with past-year STI diagnosis (aOR = 3.70, 95% CI: 1.33-10.32, p = 0.012) and oral sex (aOR = 0.09, 95% CI: 0.01-0.63, p = 0.015). Finally, past-year Doxy-PEP use was significantly associated with past year-STI diagnosis (aOR = 4.44, 95% CI: 2.03-9.71, p < 0.001). Results underscore the need for integrated care across primary care, pharmacy, and substance use treatment settings to improve screening, education, and prescription of HIV/STI preventative biomedical pharmaceuticals for substance-using MSM.

Awareness and willingness toward doxycycline post-exposure prophylaxis use for bacterial sexually transmitted infections among men who have sex with men

Background Doxycycline post-exposure prophylaxis (doxy-PEP) has shown efficacy in preventing bacterial sexually transmitted infections (STIs) among men who have sex with men (MSM). We aimed to investigate the awareness and willingness toward doxy-PEP among MSM in the real-world setting. Methods From October 2023 to March 2024, we enrolled MSM aged ≥18years, including people with HIV and PrEP users in Taiwan. Participants completed a questionnaire interview on sexual behaviors, STI history, and awareness and willingness to use doxy-PEP. Factors associated with willingness and doxy-PEP prescription were identified. Results Of 1100 participants (median age, 36years), 75.5% were people with HIV and 24.5% were PrEP users. Among them, 29.8% (328/1100) had heard of doxy-PEP. After education and counseling, 85.9% (945/1100) expressed willingness to use doxy-PEP and 45.6% (431/945) received prescriptions for doxy-PEP. In multivariable analysis, willingness to use doxy-PEP was associated with engaging in anal sex (AOR2.98, 95% CI1.01-8.78), having fixed sexual partners (AOR0.53, 95% CI0.34-0.82), using recreational drugs (AOR1.59, 95% CI1.01-2.50) and receiving suggestions from healthcare providers (AOR1.89, 95% CI1.22-2.91). Starting doxy-PEP was associated with having a bachelor's degree or higher (AOR1.47, 95% CI1.03-2.09), more than five sexual partners (AOR1.97, 95% CI1.18-3.27), chlamydia history (AOR1.92, 95% CI1.23-2.99), suggestions from healthcare providers (AOR 1.64, 95% CI1.10-2.45) and information from scientific research papers (AOR1.34, 95% CI1.01-1.79). Conclusions MSM in Taiwan had high willingness toward doxy-PEP, which was correlated with their at-risk sexual behavior. Understanding factors influencing willingness and counseling from healthcare providers may guide doxy-PEP implementation.

Population Prevalence and Correlates of Syphilis in Rural, Southwestern Uganda

Background

The global incidence of syphilis has increased in recent years. Understanding syphilis epidemiology will inform screening and treatment programs. However, such data are lacking in many communities. We outline a population-based syphilis screening program in a rural community in southwestern Uganda to describe the population prevalence of syphilis.

Methods

In June 2019 we conducted a cross-sectional, population-based study of adults >18 years of age. Two-stage syphilis testing was completed with Treponema pallidum hemagglutination (TPHA) rapid immunochromatographic testing, confirmed by rapid plasma reagin (RPR) in those with positive TPHA (syphilis seroprevalence). We calculate inverse probability of treatment (IPT) weights using logistic regression to estimate the population prevalence of positive TPHA. We included covariates with a univariable α = .10 in multivariable logistic regression models, stratified by sex, to estimate correlates of syphilis seroprevalence.

Results

Among 749 participants who participated in this population-based study, 724 (97%) completed syphilis screening. The median age was 42.9 years (standard deviation, 15.6 years) and 456 of 724 (63%) were women. Based on the IPT-weighted adjusted model, the syphilis population seroprevalence was 10.6% (95% confidence interval, 8.4%-13.4%). Among the 62 of 79 (78%) participants who completed RPR testing, all had titers ≤1:4. Syphilis seroprevalence was associated with less education, human immunodeficiency virus (HIV) infection, and ≥2 sexual partners in the prior month among women and with HIV among men.

Conclusions

We describe a high prevalence of current or former syphilis (10.6%) in a population-based study in rural Uganda. Syphilis screening and surveillance programs in this region require expansion to capture populations not routinely in care.

Rapid Diffusion of Awareness and Uptake of Doxy-PEP among Men who Have Sex with Men in San Francisco

In October 2022, the San Francisco Department of Public Health published guidelines for doxycycline post-exposure prophylaxis (doxy-PEP) to prevent bacterial sexually transmitted infections (STI) among men who have sex with men (MSM). We evaluated awareness and use of doxy-PEP using data from the National HIV Behavioral Surveillance in 2023 in San Francisco (N = 533). In the year following the publication of the guidelines, 66.6% of MSM reported awareness of doxy-PEP, and 19.3% had used it. Among MSM who are not living with HIV, awareness of doxy-PEP was associated with higher educational levels, condomless sex, bacterial STI diagnoses, and PrEP use; use was associated with STI diagnoses and PrEP use. Among MSM living with HIV, both awareness and use were associated with younger age. These findings indicate rapid dissemination and early adoption of doxy-PEP in a priority population in a real-world setting.

Preventing Premature Pre-Exposure Prophylaxis Discontinuation and Sexually Transmitted Infections Among Men Who Have Sex With Men (Project PEACH): Protocol for a Prospective Cohort Study

BACKGROUND

There is an ongoing syndemic of HIV and sexually transmitted infections (STIs) in the United States, particularly among men who have sex with men (MSM). We have increasingly effective and diverse measures of prevention, including various types of pre-exposure prophylaxis (PrEP) for HIV prevention and doxycycline postexposure prophylaxis (doxyPEP) for STI prevention. As options expand, we need to understand how to use a combination of these strategies and other supports for MSM to best curb the syndemic.

OBJECTIVE

We designed a patient-preference trial to understand patient preferences for PrEP and doxyPEP, how preferences may change over time, and methods for preventing premature discontinuation of PrEP.

METHODS

We enrolled HIV-negative MSM in metropolitan Atlanta, Georgia. Participants could elect to take PrEP (daily or on-demand), doxyPEP, both, or neither, along with app-based support to evaluate for risk factors of discontinuation or behavioral changes that might affect their choice of prevention methods. Participants were able to switch prevention methods at any time. Oral PrEP and doxyPEP users are currently being offered quarterly in-person or at-home HIV, syphilis, gonorrhea, and chlamydia testing along with opportunities for motivational interviewing.

RESULTS

We enrolled individuals from November 2021 to September 2023. Among 240 participants, the median age was 30 (IQR 25-35), 63% (n=150) self-identified as non-Hispanic Black, and 69% (n=166) were insured. Most participants (n=144, 60%) elected to take daily PrEP plus doxyPEP, with a smaller proportion taking on-demand PrEP plus doxyPEP (n=34, 14%) or daily PrEP without doxyPEP (n=33, 14%).

CONCLUSIONS

We designed an ongoing study to evaluate the preferences for PrEP and doxyPEP among MSM in metropolitan Atlanta. Enrollment was completed in 22 months and included a diverse cohort of MSM that will be followed longitudinally to evaluate prevention preferences over time. At baseline, most participants preferred to take a combination of daily PrEP and doxyPEP for HIV and STI prevention.

TRIAL REGISTRATION

Clinicaltrials.gov NCT05072093; https://clinicaltrials.gov/study/NCT05072093.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/56096.

Staphylococcus aureus Tetracycline Resistance and Co-resistance in a Doxycycline Postexposure Prophylaxis-Eligible Population

Among doxycycline postexposure prophylaxis (doxy-PEP)-eligible men, Staphylococcus aureus tetracycline nonsusceptibility is more prevalent than in the overall population and is associated with resistance to trimethoprim-sulfamethoxazole and clindamycin. Doxy-PEP may select for multidrug-resistant S aureus, underscoring the importance of surveillance.

Revisiting the potential impact of doxycycline post-exposure prophylaxis on the selection of doxycycline resistance in Neisseria commensals

Doxycycline post-exposure prophylaxis (doxy-PEP) is a strategy to reduce bacterial sexually transmitted infections. However, the impact of doxy-PEP on resistance emergence is as of yet unclear. Commensal Neisseria are known reservoirs of resistance for gonococci through horizontal gene transfer (HGT), and are more likely to experience bystander selection from doxy-PEP as they are universally carried. The consequences of doxycycline selection on commensal Neisseria will be critical to investigate to understand possible resistance mechanisms that may be transferred to an important human pathogen. Here, collection of commensals from human hosts demonstrated 46% of isolates carry doxycycline resistance; and doxycycline resistance was significantly greater in participants self-reporting doxycycline use in the past 6 months. High-level doxycycline resistance (> 8 µg/mL) was always associated with the ribosomal protection protein (tetM) and pConj. In vitro selection of Neisseria commensals (N. cinerea, N. canis, N. elongata, and N. subflava) resulted in 12 of 16 lineages evolving doxycycline resistance (> 1 µg/mL). An A46T substitution in the repressor of the Mtr efflux pump (MtrR) and a V57M substitution in the 30 ribosomal protein S10 were associated with elevated MICs. Mutations in ribosomal components also emerged (i.e., 16 S rRNA G1057C, RplX A14T). We find the MtrR 46T, RpsJ 57M, and RplX 14T in natural commensal populations. In vitro co-evolution of N. gonorrhoeae with Neisseria commensals demonstrated rapid transfer of the pConj plasmid to N. subflava and N. cinerea, and pbla to N. cinerea. This work underscores the importance of commensal Neisseria as reservoirs of doxycycline resistance, and demonstrates a link between doxycycline use and the emergence of resistance. Though novel chromosomal resistance mutations are nominated herein, resistance emergence in natural commensal populations appears to be mainly associated with acquisition of the tetM gene. A secondary danger to pConj acquisition, is spread of pbla and β-lactam resistance, which we demonstrate here in vitro. Ultimately, characterizing the contemporary prevalence of doxycycline resistance, and underlying resistance mechanisms, in commensal communities may help us to predict the long-term impact of doxy-PEP on Neisseria, and the likelihood of transferring resistance across species' boundaries.

A quinolone N-oxide antibiotic selectively targets Neisseria gonorrhoeae via its toxin-antitoxin system

Gonorrhoea is a major sexually transmitted infection and the emergence of multidrug-resistant Neisseria gonorrhoeae poses a global health threat. To identify candidate antibiotics against N. gonorrhoeae, we screened Pseudomonas aeruginosa-derived secondary metabolites and found that 2-nonyl-4-quinolone N-oxide (NQNO) abrogated growth of N. gonorrhoeae in vitro. NQNO did not impair growth of commensal Neisseriae, vaginal lactobacilli or viability of human cells. Mechanistically, NQNO disrupted the electron transport chain, depleted ATP and NADH levels and increased oxidative stress. This triggered activation of a toxin-antitoxin system, release of the endogenous Zeta1 toxin and bacterial death. In a mouse model of infection, topical application of NQNO prevented colonization by N. gonorrhoeae. Chemical modification yielded 3-methyl NQNO, which exhibited nanomolar potency against multidrug-resistant strains, lack of resistance development and significantly reduced pathogen numbers during experimental infection of mice. These findings show the potential for selective killing of bacterial pathogens such as multidrug-resistant N. gonorrrhoeae through activation of endogenous toxins.

Doxycycline pre-exposure prophylaxis prevents sexually transmitted infections without affecting vaginal bacterial flora in female sex workers

Background

Bacterial sexually transmitted infections (STIs) like syphilis, chlamydia and gonorrhoea are often asymptomatic but can cause severe complications, including infertility and vertical transmission in cisgender women, particularly female sex workers (FSWs). Sex work is strongly associated with syphilis, with FSWs representing 38% of syphilis cases among Japanese women in 2021. Despite doxycycline's proven effectiveness in preventing bacterial STIs, its efficacy in high-risk cisgender women remains inconclusive, highlighting the need for targeted STI prevention strategies in this population.

Objectives

We investigated the effectiveness of doxycycline pre-exposure prophylaxis (doxyPrEP) in preventing STIs and its impact on vaginal flora among FSWs.

Participants and methods

This retrospective study included 40 FSWs aged ≥18 years who initiated doxyPrEP (100 mg/day) for STI prevention at a private clinic in Tokyo, Japan, between 1 October 2022 and 14 November 2023. Incidence rate ratios (IRR) for chlamydia, gonorrhoea, syphilis, bacterial vaginosis (BV), and vulvovaginal candidiasis (VVC) were estimated using fixed-effects Poisson regression models. Adherence, side effects, and satisfaction were evaluated through follow-up clinical evaluations.

Results

Overall STI incidence significantly declined from 232.3 to 79.2/100 person-years following doxyPrEP initiation (IRR = 0.33, P = 0.020). The reduction in chlamydia showed marginal statistical significance (IRR = 0.35, P = 0.056), and syphilis cases dropped to zero. Gonorrhoea, BV, and VVC incidence showed no significant changes. Follow-up clinical evaluations indicated high adherence to doxyPrEP, no serious adverse events, and high satisfaction with doxyPrEP.

Conclusions

DoxyPrEP significantly reduced the overall STI incidence among FSWs without increasing other vaginal infections.

Pilot Findings From the First Legalized Mobile Retail Pharmacy Clinic in the United States for Infectious Disease Treatment and Prevention Tailored to Reach People Who Use Drugs

Background

Mobile retail pharmacies were legalized in Connecticut in 2023 to provide primary care, human immunodeficiency virus (HIV) and hepatitis C virus (HCV) testing, preexposure prophylaxis (PrEP), immediate HIV antiretroviral therapy (ART), and medications for substance use disorders directly to people who use drugs (PWUD).

Methods

InMOTION mobile pharmacy and clinic (MPC) pilot findings describe services provided by pharmacists, clinicians, and community health workers.

Results

From 13 December 2023 through 5 November 2024, the MPC engaged with 414 participants, of whom 43% were female, 26% Black/African American, 32% uninsured, and 37% unhoused or unstably housed. Fifty-one had a previous diagnosis of an opioid use disorder (OUD), 163 accepted screening, 1 received a new diagnosis of moderate to severe OUD, and 37 received medication for OUD. Nine participants requested sexually transmitted infection testing; 3 people had positive results, all were prescribed treatment, and 1 received doxycycline postexposure prophylaxis. Four people had existing HIV diagnoses; 166 accepted rapid point-of-care (POC) testing, resulting in 1 positive test; all received ART (2 oral, 3 injectable); 9 who tested HIV negative accepted PrEP, and 1 accepted the injectable formulation. Twenty-two had known HCV, 157 accepted rapid POC HCV testing, 9 tested positive for HCV antibodies, and 11 underwent HCV viral load (VL) testing; 1 self-cleared, and 8 of 10 with detectable HCV VL received direct-acting antivirals from the MPC. Six were treated for xylazine-related wounds.

Conclusions

Health services delivered through an MPC demonstrate the potential to address healthcare gaps for PWUD and warrant exploration and expansion.

Doxycycline to prevent bacterial sexually transmitted infections in the USA: final results from the DoxyPEP multicentre, open-label, randomised controlled trial and open-label extension

BACKGROUND

Doxycycline post-exposure prophylaxis (doxy-PEP) is a promising intervention to reduce bacterial sexually transmitted infections (STIs). We evaluated the effect of doxy-PEP on STI incidence and antimicrobial resistance in men who have sex with men and transgender women for up to 12 months of follow-up, inlcuding an open-label extension.

METHODS

DoxyPEP, an open-label trial in Seattle (WA, USA) and San Francisco (CA, USA) among men who have sex with men and transgender women with at least one bacterial STI in the past year, randomly assigned participants by clinic (with computer-generated variable block sizes) 2:1 to doxy-PEP (200 mg doxycycline delayed-release tablets 24-72 h after condomless sex) or standard care. The independent endpoint adjudication committee was masked to group assignment. The primary outcome was presence of one or more bacterial STIs (Neisseria gonorrhoeae, Chlamydia trachomatis, or early syphilis) each quarter. This outcome was assessed in the modified intention-to-treat cohort, which included participants with at least one follow-up quarter (ie, ∼3 months) in their as-randomised assignment. After early termination of the randomised phase for efficacy, all participants still enrolled were offered doxy-PEP in an open-label extension (OLE). We report quarterly incidence of bacterial STIs for the as-randomised and OLE periods. Safety was assessed in all participants with any follow-up data. The trial was registered with ClinicalTrials.gov (NCT03980223) and is completed.

FINDINGS

From Aug 19, 2020, to May 13, 2022, we enrolled 637 participants; 592 participants completed at least one follow-up quarter in the randomised phase (411 in the doxy-PEP group and 181 in the standard-care group) and 282 in the OLE phase (207 in the doxy-PEP group and 82 in the standard-care group). STIs were present in 129 (12·0%) of 1077 quarters in the doxy-PEP group versus 139 (30·5%) of 455 quarters in the standard-care group during the as-randomised period, showing an absolute difference of 19 percentage points and a relative risk of 0·39 (95% CI 0·31-0·49, p<0·0001). During the OLE, STIs were diagnosed in 51 (13%) of 388 quarters among those continuing doxy-PEP and 25 (17%) of 145 quarters among standard-care participants who initiated doxy-PEP. Throughout all quarters for participants on doxy-PEP, there was one grade 2 laboratory abnormality and five grade 3 adverse events that were possibly or probably related to doxy-PEP. No serious adverse events were attributed by site investigators to doxycycline. Of participants with positive gonorrhoea cultures during the study, eight (27%) of 29 taking doxy-PEP versus five (24%) of 21 not taking doxy-PEP had tetracycline resistance (minimum inhibitory concentration ≥2 μg/mL).

INTERPRETATION

Doxy-PEP was effective in reducing bacterial STIs in this population of men who have sex with men and transgender women, including during an open-label extension when doxy-PEP efficacy was known. Doxy-PEP was well tolerated, highly acceptable, and with no new safety signals.

FUNDING

US National Institutes of Health.

In Vitro Exposure of Treponema pallidum to Subbactericidal Doxycycline Did Not Induce Resistance: Implications for Doxycycline Postexposure Prophylaxis

Doxycycline postexposure prophylaxis (doxy-PEP) could significantly reduce syphilis incidence. However, the increase in intermittent doxycycline usage might select resistant Treponema pallidum strains. To assess whether resistance to doxycycline could be induced in this pathogen, we exposed the SS14 strain in vitro, both intermittently and continuously, to a subbactericidal doxycycline concentration that still exerts antibiotic pressure. During and after each exposure experiment, we assessed the doxycycline minimal inhibitory concentration in test and control treponemes and performed whole-genome sequencing, concluding that no resistance developed. This work suggests that doxycycline-resistant T. pallidum is not an immediate threat for doxy-PEP implementation.

Doxycycline Postexposure Prophylaxis and Sexually Transmitted Infection Trends

Importance

Increasing rates of sexually transmitted infections (STIs) have been associated with rises in serious morbidity. While doxycycline postexposure prophylaxis (doxyPEP), a strategy in which individuals take doxycycline, 200 mg, after condomless sex to prevent bacterial STIs, has been shown to be efficacious in randomized clinical trials, doxyPEP's potential effect on population-level STI incidence is unknown.

Objective

To assess the association of citywide doxyPEP guideline release with reported chlamydia, gonorrhea, and early syphilis cases in men who have sex with men (MSM) and in transgender women in San Francisco, California.

Design, Setting, and Participants

This population-level interrupted time series analysis of reported San Francisco STI cases measured monthly cases of chlamydia, gonorrhea, and early syphilis prior to (July 2021-October 2022) and after (November 2022-November 2023) release of citywide doxyPEP guidelines in October 2022. All reported chlamydia, gonorrhea, and early syphilis cases among MSM and transgender women in San Francisco during the period of analysis were included. Data were analyzed November 2023 to July 2024.

Exposure

Release of doxyPEP citywide guidelines.

Main Outcomes and Measures

The primary outcome was the percentage change between projected and observed chlamydia, gonorrhea, and early syphilis cases in the 13-month postexposure period.

Results

Citywide, there were 6694 cases of chlamydia, 9603 cases of gonorrhea, and 2121 cases of early syphilis among MSM and transgender women during the analytic period. STI cases among MSM and transgender women decreased significantly compared with model projections for chlamydia (-6.58% per month; 95% CI, -7.99% to -5.16%) and early syphilis (-2.68% per month; 95% CI, -3.75% to -1.60%) after doxyPEP implementation. By the end of the 13-month postperiod in November 2023, chlamydia and early syphilis cases decreased -49.64% (95% CI, -59.05% to -38.06%) and -51.39% (95% CI, -58.21% to -43.46%), respectively, compared with projected cases. There was a significant increase in monthly gonorrhea cases compared with projections (1.77% per month; 95% CI, 0.87% to 2.67%).

Conclusions and Relevance

This study suggests that San Francisco's doxyPEP guideline release was associated with decreases in reported cases of chlamydia and early syphilis, but not gonorrhea, among MSM and transgender women in San Francisco. Further analyses are needed to assess whether declines are sustained and monitor for adverse consequences, including antimicrobial resistance. Supporting doxyPEP implementation for MSM and transgender women at risk for STIs could have a significant impact on the nationwide STI epidemic.

DOXY do, or DOXY Don't? Syphilis and doxycycline post-exposure prophylaxis: A case report

The resurgence of syphilis across Europe has led to a growing number of atypical cases, often characterised by varied symptoms that can delay diagnosis. We report the case of a young man who has sex with men (MSM), presenting with persistent headaches and swelling of the forehead suggestive of giant cell arteritis (GCA). Despite a recent negative syphilis test, further investigations confirmed the diagnosis of neurosyphilis. The patient had been using doxycycline post-exposure prophylaxis (DoxyPEP), which is suspected to have delayed the diagnosis by masking the typical antibody response. This case highlights concerns about DoxyPEP's impact on syphilis detection and disease progression. Further research is warranted to explore its effects on antimicrobial resistance, the human microbiome, and clinical outcomes.

Another Tool for the Sexual Health Toolkit: US Health Care Provider Knowledge and Attitudes About Doxycycline Postexposure Prophylaxis to Prevent Bacterial Sexually Transmitted Infections Among Men Who Have Sex With Men

BACKGROUND

Doxycycline post-exposure prophylaxis (doxy-PEP) reduces chlamydia, gonorrhea, and syphilis infections among men who have sex with men (MSM) and transwomen (TW). Perspectives of health care providers (HCPs) regarding doxy-PEP can inform implementation efforts.

METHODS

From August 2022 to January 2023, HCPs were recruited from 13 cities with high sexually transmitted infection (STI) rates for semi-structured, in-depth interviews about their awareness of and attitudes toward doxy-PEP for STI prevention. Health care providers were purposively sampled to include people with experience prescribing PrEP and provision of care to MSM. Interviews were conducted virtually via Zoom. Transcripts and debrief reports were analyzed using a directed content analysis approach to explore knowledge, attitudes, and beliefs about doxy-PEP.

RESULTS

Among 30 HCPs, almost half (47%) were between 31-40 years of age, 53% identified as male, and 47% reported their sexual orientation as gay or queer. Half (53%) of participants practiced in the South, 43% had >100 MSM in their clinic panel, and 17% had previously prescribed doxy-PEP. We identified four overarching themes: 1) HCPs expressed positive attitudes toward doxy-PEP; 2) antimicrobial resistance concerns limit enthusiasm for some HCPs; 3) additional data about the long-term safety of doxy-PEP would improve their confidence; and 4) development of guidelines would facilitate the prescription of doxy-PEP, including eligibility, dosing instructions, and treatment management.

CONCLUSION

HCPs were motivated to prescribe doxy-PEP with almost 20% already having prescribed it. Guidelines and data about long-term safety, especially antimicrobial resistance, would facilitate introduction of doxy-PEP into clinical practice.

Doxycycline Postexposure Prophylaxis and Bacterial Sexually Transmitted Infections Among Individuals Using HIV Preexposure Prophylaxis

Importance

Doxycycline postexposure prophylaxis (doxyPEP) has been shown to decrease the incidence of bacterial sexually transmitted infections (STIs) among people assigned male sex at birth in clinical trials, but data from clinical practice are limited.

Objective

To describe early uptake of doxyPEP and evaluate changes in STI incidence following doxyPEP initiation.

Design, Setting, and Participants

This retrospective cohort study of adults (aged ≥18 years) dispensed HIV preexposure prophylaxis (PrEP) at Kaiser Permanente Northern California during November 1, 2022, to December 31, 2023, examined electronic health record data to compare HIV PrEP users dispensed and not dispensed doxyPEP and rates of bacterial STIs before and after starting doxyPEP. Individuals were followed up from their first recorded STI test on or after November 1, 2020, until December 31, 2023, or discontinuation of health plan membership.

Exposure

Pharmacy dispensing data were used to define doxyPEP recipients.

Main Outcomes and Measures

Demographic and clinical characteristics were compared between individuals dispensed and not dispensed doxyPEP. Primary outcomes were incident chlamydia, gonorrhea, or infectious syphilis measured as quarterly STI positivity (proportion of individuals testing positive at least once per quarter). Among doxyPEP recipients, rate ratios (RRs) compared mean quarterly STI positivity from 24 months before to 12 months after starting doxyPEP. In an exploratory analysis, STI trends were evaluated for the full cohort, stratified by receipt of doxyPEP.

Results

Among 11 551 HIV PrEP users (mean [SD] age, 39.9 [12.1] years; 95.1% male), 2253 (19.5%) were dispensed doxyPEP, of whom 2228 (98.9%) were male and 1096 (48.6%) had an STI in the year before starting doxyPEP. Compared with individuals not dispensed doxyPEP, doxyPEP recipients were older (mean [SD] age, 40.4 [10.8] vs 39.8 [12.4] years; P = .04) and had used HIV PrEP longer (mean [SD], 4.2 [2.8] vs 3.4 [2.6] years; P < .001), and a higher proportion were commercially insured (2091 [92.8%] vs 8270 [88.9%]; P < .001). Among doxyPEP recipients, quarterly chlamydia positivity decreased from 9.6% (95% CI, 9.0%-10.3%) before starting doxyPEP to 2.0% (95% CI, 1.5%-2.6%) after starting doxyPEP (RR, 0.21; 95% CI, 0.16-0.27; P < .001), with significant declines for each anatomic site of infection. Quarterly gonorrhea positivity decreased from 10.2% (95% CI, 9.6%-10.9%) before starting doxyPEP to 9.0% (95% CI, 8.0%-10.1%) after starting doxyPEP (RR, 0.88; 95% CI, 0.77-1.00; P = .048); site-specific declines were significant for rectal (RR, 0.81; 95% CI, 0.67-0.97; P = .02) and urethral (RR, 0.56; 95% CI, 0.40-0.79; P = .001) gonorrhea, but not pharyngeal gonorrhea. Quarterly syphilis positivity decreased from 1.7% (95% CI, 1.4%-1.9%) before starting doxyPEP to 0.3% (95% CI, 0.2%-0.6%) after starting doxyPEP (RR, 0.20; 95% CI, 0.11-0.37; P < .001). Positivity for STIs remained stable in individuals not dispensed doxyPEP.

Conclusions and Relevance

This study found that receipt of doxyPEP was associated with substantial declines in chlamydia and syphilis incidence and modest declines in urethral and rectal gonorrhea incidence among individuals using HIV PrEP. These findings suggest that doxyPEP may offer substantial benefits for reducing population-level STI transmission with broader implementation.

DoxyPEP Implementation Preferences for Bacterial STD Prevention Among Gay, Bisexual, and Other Men Who Have Sex with Men Living With and Without HIV in Los Angeles: A Mixed-Methods Approach

Bacterial sexually transmitted diseases (STDs) remain prominent in the United States among gay, bisexual, and other men who have sex with men (GBMSM). Doxycycline for post-exposure prophylaxis (DoxyPEP) is a regimen by which the antibiotic doxycycline is taken after sex to prevent bacterial STDs, such as, chlamydia, gonorrhea, and syphilis. Despite this, this study was conducted because there are a limited number of publications that describe GBMSM's knowledge of, and interest in, taking DoxyPEP and preferences regarding its implementation. We conducted a mixed-methods study between November 2023 and March 2024. Participants (N = 21) completed a semi-structured interview and survey and were eligible if they were a cisgender man who reported having anal sex with another man in the past year and lived in the greater Los Angeles area. Interviews were recorded and transcribed and were analyzed using thematic content analysis. The majority of participants identified as gay (90%) and a racial/ethnic minority (86%); 33% were living with HIV and 43% had been diagnosed with an STD in the prior year. Participants' mean age was 40 years (standard deviation [SD] = 15) and they reported an average of 4.5 (SD = 2.27) sexual partners in the past year. Interviews revealed that knowledge of DoxyPEP was low (28%), but most (81%) were interested in using DoxyPEP after learning about its potential. The vast majority were willing to pay $10-$20 for a 1-month supply but preferred that it be free or covered by insurance. Most preferred to get DoxyPEP from a medical provider or over-the-counter at a pharmacy. Others suggested sexualized venues, such as private sex parties, bathhouses, sex clubs, etc. The greatest concerns about its use included possible side effects, antibiotic resistance, or that it would lead to decreased condom use and increased number of sex partners. A common misconception was that DoxyPEP could prevent both a bacterial STD and HIV. DoxyPEP has strong potential as a widely accepted STD prevention method, but its successful adoption will require proactive strategies to increase GBMSM's knowledge. Implementation programs might consider nontraditional venues where sex between men is regularly occurring.

Promises, Pitfalls, and Progress: Doxycycline Prophylaxis for Bacterial Sexually Transmitted Infections

PURPOSE OF REVIEW

Doxycycline post-exposure prophylaxis (doxy PEP) has proven to be highly effective in reducing the incidence of sexually transmitted infections (STIs) among men who have sex with men (MSM) and transgender women. In response, the US Centers for Disease Control and Prevention (CDC) issued official clinical guidance on the use of doxy PEP as a preventive intervention in these populations. However, despite strong evidence supporting its use, the potential risks of antimicrobial resistance (AMR) along with its limited accessibility in other key populations, remain significant concerns with doxy PEP.

RECENT FINDINGS

Real-world data show strong awareness, interest, and usage of doxy PEP among MSM and transwomen. Early ecological studies have revealed population-level reductions in chlamydia and early syphilis incidence following doxy PEP implementation. Ongoing research continues to explore its efficacy in other populations, as well as its impact on both individual and population-level AMR. Doxy PEP is a well-tolerated and inexpensive intervention that has the potential to substantially reduce bacterial STIs, particularly in priority populations. Its implementation will require careful assessment of equitable uptake, usage patterns, and long-term monitoring of STI incidence and AMR.

High Incidence and Duration of Antibiotic Use Among a Cohort of Men Who Have Sex With Men in Seattle, Washington

Background

Doxycycline postexposure prophylaxis (doxy-PEP) effectively prevents bacterial sexually transmitted infections (STIs) but may increase antibiotic pressure. Little is known about longitudinal antibiotic use among men who have sex with men (MSM), a key population for doxy-PEP.

Methods

We analyzed data from a prospective cohort of MSM in Seattle, Washington, from 2016 to 2018, prior to the introduction of doxy-PEP. Antibiotic use and reason for prescription were self-reported in weekly surveys and extracted from medical records. We characterized antibiotic use across 49 weeks of follow-up, stratified by specific antibiotics of interest and reasons for prescription. Incidence rates (IRs) were calculated for the number of incident events of antibiotic initiation per 100 person-years (PY) at risk. We assessed factors associated with antibiotic initiation using negative binomial regression to estimate adjusted incidence rate ratios (IRRs).

Results

Among 140 participants, 68.6% (n = 96) received at least 1 antibiotic during follow-up, resulting in an overall IR of 264.5 events of antibiotic initiation per 100 PY and 1696 total days of antibiotic use. STI treatment was the most common reason for antibiotic initiation (IR, 153.5 events per 100 PY; 462 days); however, treatment for other conditions contributed most to overall days of antibiotic use (IR, 42.6 events per 100 PY; 947 days). An age of 25-39 years (IRR, 1.54 [95% confidence interval {CI}, 1.02-2.32]) and a history of bacterial STIs <12 months prior to enrollment (IRR, 1.81 [95% CI, 1.12-2.93]) were significantly associated with higher incidence of antibiotic initiation.

Conclusions

Antibiotic consumption among this population was very high. Our analysis provides a necessary foundation for assessing the potential impacts of doxy-PEP.

Efficacy of Doxycycline as Preexposure and/or Postexposure Prophylaxis to Prevent Sexually Transmitted Diseases: A Systematic Review and Meta-Analysis

INTRODUCTION

Bacterial sexually transmitted infections (STIs), specifically infection by Chlamydia trachomatis , Neisseria gonorrhoeae , and Treponema pallidum , have an important burden worldwide. The use of doxycycline as preexposure prophylaxis (PREP or doxy-PREP) or postexposure prophylaxis (PEP or doxy-PEP) might be effective as prophylaxis because it is effective against C. trachomatis and T. pallidum .

AIMS

Our objective was to evaluate the efficacy of doxycycline as PREP or PEP against bacterial STIs ( C. trachomatis , N. gonorrhoeae , and T. pallidum ).

METHODS

A systematic review and meta-analysis of randomized clinical trials of a high-risk group of individuals was conducted to evaluate whether doxycycline is as effective as PREP or PEP in preventing bacterial STIs. The PubMed-MEDLINE (MEDlars online), Cohrane, Scientific Electronic Library Online (SciELO), and Latin America and the Caribbean Literature on Health Sciences ( Literatura Latino-Americana e do Caribe em Ciências da Saúde -LILACS) databases were searched for randomized clinical trials published up to March 2024. Data were extracted from published reports. Hazard ratios (HRs) and risk ratios (RRs) with 95% confidence interval (CI) were pooled across trials.

MAIN OUTCOME MEASURE

The primary end points were any incidence of bacterial STIs and individual STI infections.

RESULTS

A total of 4 studies were included in the analysis, 3 of which evaluated doxy-PEP and 1 evaluated doxy-PREP. In the doxy-PEP group, a total of 1182 participants were evaluated. In the pooled analysis of doxy-PEP studies, the incidence of the first STI was lower in the doxy-PEP group (HR, 0.538 [95% CI, 0.337-0.859]; I2 = 77%; P < 0.05). Regarding individual infections, only 2 studies were included. In the doxy-PEP group, the incidence of individual infection of C. trachomatis was lower compared with controls (RR, 0.291 [95% CI, 0.093-0.911]) ( I2 = 89%; P < 0.05). Because only one study evaluated doxy-PREP, it was not possible to calculate a meta-analysis index; however, the use of doxycycline as PREP was associated with a decrease in the rate of any STI.

CONCLUSIONS

The use of doxy-PEP might reduce the first STI, mainly C. trachomatis , if used within 72 hours after condomless sex. The use of doxy-PREP might also decrease the chance of any STI; however, only 1 study was evaluated.

Utilization of Doxycycline Postexposure Prophylaxis at a Midwestern United States HIV/PrEP Clinic

Appropriate, protocol-adherent, doxycycline postexposure prophylaxis prescribing occurred for 70% of prescriptions from our clinic. Most of the nonadherent prescribing was due to missed sexually transmitted infection screenings (89%). As utilization of doxycycline postexposure prophylaxis continues to increase, it is necessary to ensure appropriate follow-up and monitoring.

Efficacy of postexposure prophylaxis with doxycycline (Doxy-PEP) in reducing sexually transmitted infections: a systematic review and meta-analysis

OBJECTIVES

This systematic review aimed to identify the efficacy, adherence, safety and impact on antimicrobial resistance of postexposure prophylaxis with doxycycline (Doxy-PEP) in different populations.

METHODS

We searched MEDLINE (via PubMed), Embase and Cochrane CENTRAL databases from inception to 29 May 2024. Two reviewers independently screened the studies and extracted data. We included randomised clinical trials that evaluated the efficacy of Doxy-PEP within 72 hours after condomless sex. A random-effects meta-analysis was conducted to compare the risk of bacterial sexually transmitted infections (STIs) between Doxy-PEP and no prophylaxis. The risk of bias was assessed with the risk-of-bias tool for randomized trials (RoB 2) and the certainty of evidence (CoE) with Grading of Recommendations Assessment, Development and Evaluation (GRADE).

RESULTS

Four studies were included in the systematic review, totalling 1727 participants. Studies were conducted between 2015 and 2022. Most participants (73%) were men who have sex with men, and the median age of participants varied from 24 to 43 years. Doxy-PEP reduced the risk of having any bacterial STI in different populations by 46% (hazard ratio (HR) 0.54; 95% CI 0.39 to 0.75; CoE moderate), the risk of chlamydia by 65% (relative risk (RR) 0.35; 95% CI 0.15 to 0.82; CoE low) and syphilis by 77% (RR 0.23; 95% CI 0.13 to 0.41; CoE high), without significant effect for risk of gonorrhoea infection (RR 0.90; 95% CI 0.64 to 1.26; CoE very low). The self-reported adherence rate of Doxy-PEP was approximately 80% and one drug-related serious adverse event was reported.

CONCLUSION

Doxy-PEP reduced the incidence of chlamydia and syphilis infections. No significant reduction in gonorrhoea infection was observed. This strategy seems promising for some high-risk groups; however, there is still a lack of information on the induction of bacterial resistance and long-term adverse events.

PROSPERO REGISTRATION NUMBER

CRD42023454123.

Doxycycline Postexposure Prophylaxis to Prevent Bacterial Sexually Transmitted Infection

This JAMA Guidelines Synopsis summarizes the 2024 Centers for Disease Control and Prevention guidelines on use of doxycycline postexposure prophylaxis (doxyPEP) for bacterial sexually transmitted infection prevention.

Terminal complement complexes with or without C9 potentiate antimicrobial activity against Neisseria gonorrhoeae

The complement cascade is a front-line defense against pathogens. Complement activation generates the membrane attack complex (MAC), a 10-11 nm diameter pore formed by complement proteins C5b through C8 and polymerized C9. The MAC embeds within the outer membrane of Gram-negative bacteria and displays bactericidal activity. In the absence of C9, C5b-C8 complexes can form 2-4 nm pores on membranes, but their relevance to microbial control is poorly understood. Deficiencies in terminal complement components uniquely predispose individuals to infections by pathogenic Neisseria, including N. gonorrhoeae (Gc). Increasing antibiotic resistance in Gc makes new therapeutic strategies a priority. Here, we demonstrate that MAC formed by complement activity in human serum disrupts the Gc outer and inner membranes, potentiating the activity of antimicrobials against Gc and re-sensitizing multidrug resistant Gc to antibiotics. C9-depleted serum also disrupts Gc membranes and exerts antigonococcal activity, effects that are not reported in other Gram-negative bacteria. C5b-C8 complex formation potentiates Gc sensitivity to azithromycin but not lysozyme. These findings expand our mechanistic understanding of complement lytic activity, suggest a size limitation for terminal complement-mediated enhancement of antimicrobials against Gc, and suggest complement manipulation can be used to combat drug-resistant gonorrhea.

Importance

The complement cascade is a front-line arm of the innate immune system against pathogens. Complement activation results in membrane attack complex (MAC) pores forming on the outer membrane of Gram-negative bacteria, resulting in bacterial death. Individuals who cannot generate MAC are specifically susceptible to infection by pathogenic Neisseria species including N. gonorrhoeae (Gc). High rates of gonorrhea and its complications like infertility, and high-frequency resistance to multiple antibiotics, make it important to identify new approaches to combat Gc. Beyond direct anti-Gc activity, we found the MAC increases the ability of antibiotics and antimicrobial proteins to kill Gc and re-sensitizes multidrug-resistant bacteria to antibiotics. The most terminal component, C9, is needed to potentiate the anti-Gc activity of lysozyme, but azithromycin activity is potentiated regardless of C9. These findings highlight the unique effects of MAC on Gc and suggest novel translational avenues to combat drug-resistant gonorrhea.

Re-visiting the potential impact of doxycycline post-exposure prophylaxis (doxy-PEP) on the selection of doxycycline resistance in Neisseria commensals

Doxycycline post-exposure prophylaxis (doxy-PEP) is a preventative strategy demonstrated to reduce bacterial sexually transmitted infections in high-risk populations. However, the impact of doxy-PEP on antibiotic resistance acquisition in key members of our microbiomes, is as of yet unclear. For example, commensal Neisseria are known reservoirs of resistance for gonococci through horizontal gene transfer (HGT), and are more likely to experience bystander selection due to doxy-PEP as they are universally carried. Thus, the consequences of doxycycline selection on commensal Neisseria will be critical to investigate to understand possible resistance mechanisms that may be transferred to an important human pathogen. Here, we use in vitro antibiotic gradients to evolve four Neisseria commensals (N. cinerea, N. canis, N. elongata, and N. subflava, n=4 per species) across a 20-day time course; and use whole genome sequencing to nominate derived mutations. After selection, 12 of 16 replicates evolved doxycycline resistance (> 1 μg/mL). Across resistant lineages: An A46T substitution in the repressor of the Mtr efflux pump (MtrR) and a V57M substitution in the 30 ribosomal protein S10 were clearly associated with elevated MICs. Additional mutations in ribosomal components also emerged in strains with high MICs (i.e., 16S rRNA G1057C, RplX A14T). We find the MtrR 46T, RpsJ 57M, and RplX 14T circulating in natural commensal populations. Furthermore, in vitro co-evolution of N. gonorrhoeae with Neisseria commensals demonstrated rapid transfer of the pConj plasmid to N. subflava and N. cinerea, and pbla to N. cinerea. Finally, collection of novel commensals from human hosts reveals 46% of isolates carrying doxycycline resistance; and doxycycline resistance was significantly greater in participants self-reporting doxycycline use in the past 6 months. High-level doxycycline resistance (> 8 μg/mL) was always associated with carriage of the ribosomal protection protein (tetM) and pConj. Ultimately, characterizing the contemporary prevalence of doxycycline resistance, and underlying resistance mechanisms, in commensal communities may help us to predict the long-term impact of doxy-PEP on Neisseria, and the likelihood of transferring particular genotypes across species' boundaries.

Infection prevention in the immunocompromised traveler due to conditions other than transplantation: a review

This narrative review explores the risks related to infection in immunocompromised travelers due to conditions other than transplantation, and evaluates the evidence behind current prophylactic strategies, including immunizations, antimicrobials, and non-pharmacological interventions, to prevent various infection and how the current evidence applies to this special patient population, from the perspective of a US-based traveler.

Doxycycline Postexposure Prophylaxis (DoxyPEP) for Bacterial STI Prevention

This Viewpoint describes what dermatologists should know about doxycycline postexposure prophylaxis (doxyPEP) for bacterial sexually transmitted infection (STI) prevention, specifically syphilis, chlamydia, and gonorrhea.

Part II: Skin signs of human trafficking and intervention by dermatologists

Human trafficking is a pervasive global health and human rights issue. The skin often bears the early and most visible signs of abuse and exploitation. Despite the visible nature of their trauma, affected patients frequently go unrecognized within health care settings due to a lack of standardized guidelines for identifying the dermatologic manifestations of trafficking. Herein, we address these challenges by equipping dermatologists and health care teams with the necessary tools to recognize, treat, and report the skin signs of human trafficking. In doing so, we hope to emphasize the importance of early identification and intervention, as well as bring awareness to critical signs, including dermatologic evidence of abuse, infectious diseases, sexually transmitted infections, substance use, and branding. In understanding this, we can bring awareness to dermatologists' critical role in caring for this patient population and their associated cutaneous manifestations. By advancing knowledge in this area, we hope to enhance the capacity of dermatologists to support trafficked individuals.

Knowledge, uptake and intention to use antibiotic post-exposure prophylaxis and meningococcal B vaccine (4CMenB) for gonorrhoea among a large, online community sample of men and gender-diverse individuals who have sex with men in the UK

Novel STI prevention interventions, including doxycycline post-exposure prophylaxis (doxyPEP) and meningococcal B vaccination (4CMenB) against gonorrhoea, have been increasingly examined as tools to aid STI control. There is evidence of the efficacy of doxyPEP in preventing bacterial STIs; however, limited data exist on the extent of use in the UK. We examined self-reported knowledge and use of antibiotic post-exposure prophylaxis (PEP), and intention to use (ITU) doxyPEP and 4CMenB among a large, community sample of men and gender-diverse individuals who have sex with men in the UK. Using data collected by the RiiSH survey (November/December 2023), part of a series of online surveys of men and other gender-diverse individuals in the UK, we describe (%, [95% CI]) self-reported knowledge and use of antibiotic PEP (including doxyPEP) and doxyPEP and 4CMenB ITU. Using bivariate and multivariable logistic regression, we examined correlates of ever using antibiotic PEP, doxyPEP ITU, and 4CMenB ITU, respectively, adjusting for sociodemographic characteristics and a composite marker of sexual risk defined as reporting (in the last three months): ≥5 condomless anal sex partners, bacterial STI diagnosis, chemsex, and/or meeting partners at sex-on-premises venues, sex parties, or cruising locations. Of 1,106 participants (median age: 44 years [IQR: 34-54]), 34% (30%-37%) knew of antibiotic PEP; 8% (6%-10%) ever reported antibiotic PEP use. Among those who did, most reported use in the last year (84%, 73/87) and exclusively used doxycycline (69%, 60/87). Over half of participants reported doxyPEP ITU (51% [95% CI: 47%-56%], 568/1,106) while over two-thirds (64% [95% CI: 60%-69%], 713/1,106) reported 4CMenB ITU. Participants with markers of sexual risk and with uptake of other preventative interventions were more likely to report ever using antibiotic PEP as well as doxyPEP and 4CMenB ITU, respectively. HIV-PrEP users and people living with HIV (PLWHIV) were more likely to report antibiotic PEP use and doxyPEP and 4CMenB vaccination ITU than HIV-negative participants not reporting recent HIV-PrEP use. Findings demonstrate considerable interest in the use of novel STI prevention interventions, more so for 4CMenB vaccination relative to doxyPEP. Fewer than one in ten participants had reported ever using antibiotic PEP, with most using appropriate, evidence-based antibiotics. The use of antibiotic PEP and the report of doxyPEP ITU and 4CMenB ITU was more common among those at greater risk of STIs.

From Cure to Prevention: Doxycycline's Potential in Prophylaxis for Sexually Transmitted Infections

Over the past two decades, the global incidence of sexually transmitted infections (STIs) such as gonorrhea, chlamydia, and syphilis have increased significantly, particularly among cisgender men who have sex with men (MSM) and transgender women (TGW). This rise in STIs has spurred interest in new preventive measures, including doxycycline post-exposure prophylaxis (DoxyPEP). Clinical trials in the United States and France have demonstrated the effectiveness of DoxyPEP in reducing both chlamydia and syphilis incidence among MSM and TGW; although, its efficacy against gonorrhea remains limited, and it was further found to be ineffective among cisgender women in Kenya. Due to the promising results, the CDC and the German STI Society have incorporated DoxyPEP into their guidelines for specific high-risk groups. However, the broader implementation of DoxyPEP presents several challenges and ethical concerns. Key issues involve the potential development of antimicrobial resistance, particularly among common STI pathogens like C. trachomatis, M. genitalium, and N. gonorrhoeae, as well as other bacteria such as S. aureus and K. pneumoniae. Additionally, questions concerning equitable healthcare access, the potential impact on adherence to safer sex practices, and broader public health implications warrant careful consideration. Addressing these challenges necessitates a careful balance between the benefits and risks of DoxyPEP, as well as the implementation of strategies to mitigate negative outcomes while maximizing the impact on public health. Lastly, future research should explore the integration of DoxyPEP with other preventive strategies, such as vaccines, to enhance its effectiveness and reduce the global burden of STIs.

Use of Doxycycline and Other Antibiotics as Bacterial Sexually Transmitted Infection Prophylaxis in a US Sample of Primarily Gay and Bisexual Men

BACKGROUND

Doxycycline used as postexposure prophylaxis (doxyPEP) within 72 hours of sex reduces the risk of bacterial sexually transmitted infections (STIs) in people assigned male sex at birth. Little is known about current use of antibiotics as STI prophylaxis in US populations likely to benefit from doxyPEP.

METHODS

We conducted an online survey in September 2023 of US adults recruited via sexual networking apps used mainly by gay and bisexual men (GBM). Respondents were asked about the use of antibiotics around the time of sex to prevent bacterial STIs.

RESULTS

Of 903 respondents, most (96.2%) identified as GBM; 19.0% were living with HIV and 42.5% were using HIV preexposure prophylaxis (PrEP). Half (49.1%) had heard of using antibiotics to prevent STIs, and 95.6% were interested in use. Overall, 21.0% had used antibiotic STI prophylaxis, and 15.9% had done so in the past year. Among those reporting any use, most (78.1%) had used doxycycline; some used amoxicillin (16.7%), azithromycin (14.5%), or other antibiotics (14.1%). Among those reporting use in the past year, 46.9% used it for some, 28.1% for most, and 25.0% for all sex acts with casual partners during that period. Most (78.3%) of STI prophylaxis users reported their condom use did not change during periods of STI prophylaxis use, 17.2% indicated their condom use declined, and 4.5% indicated their condom use increased. For doxyPEP specifically, 35.7% had heard of it, and 13.0% had used it in the past year, of whom 21.0% had used a dosage other than the 200-mg dose shown to be effective.

CONCLUSIONS

In this sample of primarily GBM, interest in bacterial STI prophylaxis was nearly universal. However, some of the use was not informed by current clinical guidance or evidence from research studies. Efforts are needed to increase awareness of effective dosing and monitor real-world use.

Novelty in the gut: a review of the gastrointestinal manifestations of syphilis

Syphilis is a systemic infection caused by the spirochete Treponema pallidum. It is transmitted during pregnancy or through sexual contact. Signs and symptoms vary depending on the clinical stage of the disease. Syphilis has been well-studied, and the introduction of penicillin has resulted in a decline in the number of new cases and deaths. Recently, however, there has been a surge in new cases in young people, especially those with human immunodeficiency virus (HIV). This epidemiological shift has been attributed to increased sexual activity, risky sexual behaviors, and immunodeficiency. There is a paucity of data on gastrointestinal (GI) manifestations of syphilis owing to its rarity and lack of physician awareness. T. pallidum can seed to any part of the GI tract, resulting in esophagitis, gastritis, hepatitis, pancreatitis, or proctocolitis. Depending on the affected part of the GI tract, syphilis can present with nausea, vomiting, painless esophageal ulcers, dysphagia, abdominal pain, weight loss due to early satiety, diarrhea, melena, hematochezia, dyschezia, or anorectal ulcers. Given its indolent clinical course and vague presentation, GI syphilis can mimic other GI disorders, which can delay diagnosis and treatment. A detailed medical history, physical examination, serological tests, and endoscopy can provide a definitive diagnosis. Syphilis and its GI complications are usually treated with long-acting intramuscular penicillin benzathine, and rarely with a 14-day course of intravenous penicillin. Herein, we describe the clinical features, etiopathogenesis, diagnosis, and treatment of GI syphilis. This primer should aid clinicians in timely diagnosis and treatment of various presentations of GI syphilis.

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.

Doxycycline Post-Exposure Prophylaxis for Bacterial Sexually Transmitted Infections: The Current Landscape and Future Directions

PURPOSE OF REVIEW

The incidence of bacterial sexually transmitted infections (STI) continues to rise particularly among men who have sex with men (MSM). Doxycycline post-exposure prophylaxis (doxy-PEP) has emerged as a promising biomedical prevention strategy. This review aims to summarize the results of recent studies, highlight the current normative guidance on the use of doxy-PEP, and discuss remaining questions.

RECENT FINDINGS

In the past decade, there have been four randomized controlled trials and three real-world analyses of doxy-PEP, which consistently demonstrated a reduction in Chlamydia trachomatis and Treponema pallidum infections among MSM. Questions remain regarding the efficacy of doxy-PEP for Neisseria gonorrhoeae infection and among cisgender women. Possible detrimental impacts include an increase in antimicrobial resistance as well as alterations to the gut microbiome Doxy-PEP is an effective strategy for preventing Chlamydia trachomatis and Treponema pallidum among MSM. Further work is needed to investigate the benefits among other populations, as well as to monitor for adverse effects.

Influenza vaccine effectiveness against medically attended outpatient illness, United States, 2023-24 season

Background

The 2023-24 U.S. influenza season was characterized by a predominance of A(H1N1)pdm09 virus circulation with co-circulation of A(H3N2) and B/Victoria viruses. We estimated vaccine effectiveness (VE) in the United States against mild-to-moderate medically attended influenza illness in the 2023-24 season.

Methods

We enrolled outpatients aged ≥8 months with acute respiratory illness in 7 states. Respiratory specimens were tested for influenza type/subtype by reverse-transcriptase polymerase chain reaction (RT-PCR). Influenza VE was estimated with a test-negative design comparing odds of testing positive for influenza among vaccinated versus unvaccinated participants. We estimated VE by virus sub-type/lineage and A(H1N1)pdm09 genetic subclades.

Results

Among 6,589 enrolled patients, 1,770 (27%) tested positive for influenza including 796 A(H1N1)pdm09, 563 B/Victoria, and 323 A(H3N2). Vaccine effectiveness against any influenza illness was 41% (95% Confidence Interval [CI]: 32 to 49): 28% (95% CI: 13 to 40) against influenza A(H1N1)pdm09, 68% (95% CI: 59 to 76) against B/Victoria, and 30% (95% CI: 9 to 47) against A(H3N2). Statistically significant protection against any influenza was found for all age groups except adults aged 50-64 years. Lack of protection in this age group was specific to influenza A-associated illness. We observed differences in VE by birth cohort and A(H1N1)pdm09 virus genetic subclade.

Conclusions

Vaccination reduced outpatient medically attended influenza overall by 41% and provided protection overall against circulating influenza A and B viruses. Serologic studies would help inform differences observed by age groups.