Understanding adaptive responses in PrEP service delivery in Belgian HIV clinics: a multiple case study using an implementation science framework.

INTRODUCTION: In Belgium, oral HIV pre-exposure prophylaxis (PrEP) is primarily provided in specialized clinical settings. Optimal implementation of PrEP services can help to substantially reduce HIV transmission. However, insights into implementation processes, and their complex interactions with local context, are limited. This study examined factors that influence providers' adaptive responses in the implementation of PrEP services in Belgian HIV clinics. METHODS: We conducted a qualitative multiple case study on PrEP care implementation in eight HIV clinics. Thirty-six semi-structured interviews were conducted between January 2021 and May 2022 with a purposive sample of PrEP care providers (e.g. physicians, nurses, psychologists), supplemented by 50 hours of observations of healthcare settings and clinical interactions. Field notes from observations and verbatim interview transcripts were thematically analysed guided by a refined iteration of extended Normalisation Process Theory. RESULTS: Implementing PrEP care in a centralized service delivery system required considerable adaptive capacity of providers to balance the increasing workload with an adequate response to PrEP users' individual care needs. As a result, clinic structures were re-organized to allow for more efficient PrEP care processes, compatible with other clinic-level priorities. Providers adapted clinical and policy norms on PrEP care (e.g. related to PrEP prescribing practices and which providers can deliver PrEP services), to flexibly tailor care to individual clients' situations. Interprofessional relationships were reconfigured in line with organizational and clinical adaptations; these included task-shifting from physicians to nurses, leading them to become increasingly trained and specialized in PrEP care. As nurse involvement grew, they adopted a crucial role in responding to PrEP users' non-medical needs (e.g. providing psychosocial support). Moreover, clinicians' growing collaboration with sexologists and psychologists, and interactions with PrEP users' family physician, became crucial in addressing complex psychosocial needs of PrEP clients, while also alleviating the burden of care on busy HIV clinics. CONCLUSIONS: Our study in Belgian HIV clinics reveals that the implementation of PrEP care presents a complex-multifaceted-undertaking that requires substantial adaptive work to ensure seamless integration within existing health services. To optimize integration in different settings, policies and guidelines governing PrEP care implementation should allow for sufficient flexibility and tailoring according to respective local health systems.

Ciprofloxacin Concentrations 100-Fold Lower than the MIC Can Select for Ciprofloxacin Resistance in Neisseria subflava: An In Vitro Study.

Neisseria gonorrhoeae can acquire antimicrobial resistance (AMR) through horizontal gene transfer (HGT) from other Neisseria spp. such as commensals like Neisseria subflava. Low doses of antimicrobials in food could select for AMR in N. subflava, which could then be transferred to N. gonorrhoeae. In this study, we aimed to determine the lowest concentration of ciprofloxacin that can induce ciprofloxacin resistance (minimum selection concentration-MSC) in a N. subflava isolate (ID-Co000790/2, a clinical isolate collected from a previous community study conducted at ITM). In this study, Neisseria subflava was serially passaged on gonococcal (GC) medium agar plates containing ciprofloxacin concentrations ranging from 1:100 to 1:10,000 below its ciprofloxacin MIC (0.006 µg/mL) for 6 days. After 6 days of serial passaging at ciprofloxacin concentrations of 1/100th of the MIC, 24 colonies emerged on the plate containing 0.06 µg/mL ciprofloxacin, which corresponds to the EUCAST breakpoint for N. gonorrhoeae. Their ciprofloxacin MICs were between 0.19 to 0.25 µg/mL, and whole genome sequencing revealed a missense mutation T91I in the gyrA gene, which has previously been found to cause reduced susceptibility to fluoroquinolones. The N. subflava MSCde novo was determined to be 0.06 ng/mL (0.00006 µg/mL), which is 100×-fold lower than the ciprofloxacin MIC. The implications of this finding are that the low concentrations of fluoroquinolones found in certain environmental samples, such as soil, river water, and even the food we eat, may be able to select for ciprofloxacin resistance in N. subflava.

Effect of erythromycin residuals in food on the development of resistance in Streptococcus pneumoniae: an in vivo study in Galleria mellonella.

Background: The use of antimicrobials to treat food animals may result in antimicrobial residues in foodstuffs of animal origin. The European Medicines Association (EMA) and World Health Organization (WHO) define safe antimicrobial concentrations in food based on acceptable daily intakes (ADIs). It is unknown if ADI doses of antimicrobials in food could influence the antimicrobial susceptibility of human-associated bacteria. Objectives: This aim of this study was to evaluate if the consumption of ADI doses of erythromycin could select for erythromycin resistance in a Galleria mellonella model of Streptococcus pneumoniae infection. Methods: A chronic model of S. pneumoniae infection in G. mellonella larvae was used for the experiment. Inoculation of larvae with S. pneumoniae was followed by injections of erythromycin ADI doses (0.0875 and 0.012 µg/ml according to EMA and WHO, respectively). Isolation of S. pneumoniae colonies was then performed on selective agar plates. Minimum inhibitory concentrations (MICs) of resistant colonies were measured, and whole genome sequencing (WGS) was performed followed by variant calling to determine the genetic modifications. Results: Exposure to single doses of both EMA and WHO ADI doses of erythromycin resulted in the emergence of erythromycin resistance in S. pneumoniae. Emergent resistance to erythromycin was associated with a mutation in rplA, which codes for the L1 ribosomal protein and has been linked to macrolide resistance in previous studies. Conclusion: In our in vivo model, even single doses of erythromycin that are classified as acceptable by the WHO and EMA induced significant increases in erythromycin MICs in S. pneumoniae. These results suggest the need to include the induction of antimicrobial resistance (AMR) as a significant criterion for determining ADIs.

Potential determinants of the decline in mpox cases in Belgium: a behavioral, epidemiological and seroprevalence study.

OBJECTIVE: The 2022 mpox epidemic reached a peak in Belgium and the rest of Europe in July 2022, after which it unexpectedly subsided. This study investigates epidemiological, behavioral, and immunological factors behind the waning of the epidemic in Belgium. METHODS: We investigated temporal evolutions in the characteristics and behavior of mpox patients using national surveillance data and data from a prospective registry of mpox patients in the Institute of Tropical Medicine (Antwerp). We studied behavioral changes in the population at risk using a survey among HIV-pre-exposure prophylaxis (PrEP) users. We determined the seroprevalence of anti-orthopoxvirus antibodies among HIV-PrEP users across four time points in 2022. RESULTS: Mpox patients diagnosed at the end of the epidemic had less sexual risk behavior compared to those diagnosed earlier: they engaged less in sex at mass events, had fewer sexual partners and were less likely to belong to the sexual network's central group. Among HIV-PrEP users there were no notable changes in sexual behavior. Anti-orthopoxvirus seroprevalence did not notably increase before the start of national vaccination campaigns. CONCLUSION: The observed changes in group immunity and behavior in the population at greater risk of exposure to mpox seem unable to explain the waning of the mpox epidemic. A change in the profile of mpox patients might have contributed to the decline in cases.

Could the effect of antimicrobials on antimicrobial resistance be saturated at high-antimicrobial consumption? A comparison of the MORDOR and ResistAZM studies.

OBJECTIVES: Antimicrobial resistance poses a considerable threat in high-antimicrobial-consumption populations, such as men who have sex with men (MSM) taking HIV pre-exposure prophylaxis. While the ResistAZM trial found no increase in macrolide resistance genes in MSM with gonorrhea after azithromycin treatment, the MORDOR trial observed an increase in these genes after mass azithromycin distribution. We hypothesized that this could be due to saturation of the resistome. To test this hypothesis, we compared the abundance of macrolide resistance determinants in anorectal samples between the baselines of the two trials. METHODS: Shotgun metagenome reads from the anorectal baseline samples from the ResistAZM (n = 42) and MORDOR (n = 30) trials were analyzed using AMRPlusPlus. Nonhost reads were mapped to the MEGARes database to detect antibiotic resistance genes (ARG). Antimicrobial resistance (AMR) was normalized using cumulative sum scaling, and ARG abundance was estimated. RESULTS: Macrolide, lincosamides, and streptogramins determinants were approximately 10-fold more abundant in the ResistAZM than the MORDOR samples (P ≤ 0.001). CONCLUSION: The findings are compatible with our hypothesis. Thus, in populations with high-antimicrobial use, the relationship between antimicrobial consumption and AMR may be diminished due to saturation. These findings are vital for future studies investigating the resistogencity of novel interventions, such as doxycycline post-exposure prophylaxis, in populations with high preceding consumption of antimicrobials.

Belgian 2024 guidance on the use of pre-exposure prophylaxis.

OBJECTIVES: We aimed to develop a guidance on the use of pre-exposure prophylaxis (PrEP) for HIV tailored to the Belgian context. METHODS: Different aspects of PrEP care were judged by an expert group of nine Belgian clinicians, seeking consensus for areas of controversies. RESULTS: PrEP should be considered in HIV negative patients at high risk of acquiring HIV. Currently, only oral tenofovir/emtricitabine is available in Belgium for PrEP, which can be used daily, or also event-driven in cisgender men and trans women who are not taking exogenous estradiol-based hormones. Personal counselling directed at medication adherence and sexual health should have a central role in PrEP care. At the initial assessment clinicians should give attention to symptoms of an acute HIV infection, the patients' immunization status and renal function. A regular follow-up must be set up to diagnose HIV seroconversion, treat sexually transmitted infections, and manage side effects of PrEP. CONCLUSION: The Belgian guidance on the use of PrEP provides a point of reference for standard PrEP care in Belgium and will be periodically updated.

45 years of tetracycline post exposure prophylaxis for STIs and the risk of tetracycline resistance: a systematic review and meta-analysis.

There is considerable interest in the use of doxycycline post exposure prophylaxis (PEP) to reduce the incidence of bacterial sexually transmitted infections (STIs). An important concern is that this could select for tetracycline resistance in these STIs and other species. We searched PubMed and Google Scholar, (1948-2023) for randomized controlled trials comparing tetracycline PEP with non-tetracycline controls. The primary outcome was antimicrobial resistance (AMR) to tetracyclines in all bacterial species with available data. Our search yielded 140 studies, of which three met the inclusion criteria. Tetracycline PEP was associated with an increasedprevalence of tetracycline resistance in Neisseria gonorrhoeae, but this effect was not statistically significant (Pooled OR 2.3, 95% CI 0.9-3.4). PEP had a marked effect on the N. gonorrhoeae tetracycline MIC distribution in the one study where this was assessed. Prophylactic efficacy was 100% at low MICs and 0% at high MICs. In the one study where this was assessed, PEP resulted in a significant increase in tetracycline resistance in commensal Neisseria species compared to the control group (OR 2.9, 95% CI 1.5-5.5) but no significant effect on the prevalence of tetracycline resistance in Staphylococcus aureus. The available evidence suggests that PEP with tetracyclines could be associated with selecting tetracycline resistance in N. gonorrhoeae and commensal Neisseria species.

Could traces of fluoroquinolones in food induce ciprofloxacin resistance in Escherichia coli and Klebsiella pneumoniae? An in vivo study in Galleria mellonella with important implications for maximum residue limits in food.

We hypothesized that the residual concentrations of fluoroquinolones allowed in food (acceptable daily intake-ADIs) could select for ciprofloxacin resistance in our resident microbiota. We developed models of chronic Escherichia coli and Klebsiella pneumoniae infection in Galleria mellonella larvae and exposed them to ADI doses of ciprofloxacin via single dosing and daily dosing regimens. The emergence of ciprofloxacin resistance was assessed via isolation of the target bacteria in selective agar plates. Exposure to as low as one-tenth of the ADI dose of the single and daily dosing regimens of ciprofloxacin resulted in the selection of ciprofloxacin resistance in K. pneumoniae but not E. coli. This resistance was associated with cross-resistance to doxycycline and ceftriaxone. Whole genome sequencing revealed inactivating mutations in the transcription repressors, ramR and rrf2, as well as mutations in gyrA and gyrB. We found that ciprofloxacin doses 10-fold lower than those classified as acceptable for daily intake could induce resistance to ciprofloxacin in K. pneumoniae. These results suggest that it would be prudent to include the induction of antimicrobial resistance as a significant criterion for determining ADIs and the associated maximum residue limits in food.IMPORTANCEThis study found that the concentrations of ciprofloxacin/enrofloxacin allowed in food can induce de novo ciprofloxacin resistance in Klebsiella pneumoniae. This suggests that it would be prudent to reconsider the criteria used to determine "safe" upper concentration limits in food.

Four recent insights suggest the need for more refined methods to assess the resistogenicity of doxycycline post exposure prophylaxis.

Two recently published randomized trials of doxycycline post exposure prophylaxis (PEP) have concluded that this intervention is highly effective at reducing the incidence of bacterial sexually transmitted infections (STIs) and has little or no risk of promoting the spread of antimicrobial resistance (AMR). In this perspective piece, we review four types of evidence that suggest that the risk of promoting AMR has been inadequately assessed in these studies. 1) The studies have all used proportion resistant as the outcome measure. This is a less sensitive measure of resistogenicity than MIC distribution. 2) These RCTs have not considered population-level pathways of AMR selection. 3) In populations with very high antimicrobial consumption such as PrEP cohorts, the relationship between antimicrobial consumption and resistance may be saturated. 4) Genetic linkage of AMR means that increased tetracycline use may select for AMR to not only tetracyclines but also other antimicrobials in STIs and other bacterial species. We recommend novel study designs to more adequately assess the AMR-inducing risk of doxycycline PEP.

Oral streptococcal susceptibility to azithromycin may be associated with doxycycline use: A post-hoc analysis with implications for doxycycline post exposure prophylaxis.

OBJECTIVE: Tetracycline and macrolide resistance are frequently linked in streptococci and other species. We aimed to assess the association between doxycycline use and azithromycin MICs in oral streptococci. METHODS: Linear regression was used to assess the association between doxycycline use in the prior year and the median MIC per participant of oral streptococcal colonies isolated at the baseline visit of the ResistAZM study. The analysis controlled for receipt of other antimicrobials as well as time since antimicrobial consumption. RESULTS: Fifty-six individual colonies confirmed to be streptococci were isolated from 19 individuals at baseline. The azithromycin MICs of these isolates varied considerably between 0.25 mg/L and >256 mg/L (median 28 mg/L; IQR 1-192 mg/L). The consumption of doxycycline in the preceding 12 months was positively associated with median streptococcal azithromycin MIC (coef. 151.6 [95% CI 10.6-292.7]; p = .037). CONCLUSION: This post-hoc analysis found that doxycycline use was associated with streptococcal azithromycin susceptibility. Numerous limitations of the study design mean that this study is best considered hypothesis generating. Prospective studies are required to assess if the use of doxycycline could select for macrolide resistance in oral streptococci.

Effect of mass treatment on the long-term prevalence of gonorrhoea, chlamydia and syphilis-a systematic review.

BACKGROUND: Selective mass treatment of STIs may lead to a durable reduction in the prevalence of STIs or a temporary reduction associated with an increased probability of antimicrobial resistance emerging. METHODS: We searched PubMed and Google Scholar for studies evaluating the impact of mass STI treatment on the long-term prevalence of chlamydia, gonorrhoea, syphilis and chancroid. The primary outcomes were the long term (≥3 months post the intervention) impact of the intervention on prevalence/incidence of the STI and on antimicrobial resistance. RESULTS: Our search yielded 269 studies, of which 4 met the inclusion criteria. With the exception of the Carletonville study, where this was not assessed, three of the four studies found that intensive STI treatment was associated with a reduced prevalence of the targeted STI during or immediately after the intervention. In all four studies, there was no evidence that the intense treatment had a long-term effect on prevalence. In the only study where this was assessed, the intensive use of penicillin to reduce gonococcal prevalence was associated with the emergence of reduced susceptibility to penicillin in N. gonorrhoeae. CONCLUSION: The available evidence suggests that mass treatment of chlamydia, gonorrhoea and syphilis in high prevalence populations is only associated with a temporary reduction in the prevalence of these infections and may select for antimicrobial resistance.

Self-sampling with oral rinse to detect oropharyngeal Neisseria gonorrhoeae among men who have sex with men: results from an exploratory study in Belgium (the SSONG Study).

OBJECTIVES: We aimed to assess whether a self-collected oral rinse was non-inferior to clinician-collected oropharyngeal swabs to detect Neisseria gonorrhoeae (Ng) using culture and nucleic acid amplification tests (NAAT) among men who have sex with men (MSM), and whether Ng may still be detected in oral rinses for a minimum of 5 days after collection. METHODS: MSM with a positive Ng result in an oropharyngeal or pooled sample (oropharynx, urethra and anorectum) were approached. Clinician-collected oropharyngeal swabs and oral rinses (15 mL sterile water) were taken. Ng culture and NAAT (Abbott 2000m RealTime System CT/NG assay and in-house PCR) were performed. Diagnostic accuracy was assessed using sensitivity and specificity, and agreement between both techniques using Cohen's kappa statistic. Aliquots of positive oral rinses were left at room temperature for a minimum of 5 days and reanalysed using NAAT. Lastly, participants filled in a questionnaire to explore perceptions of both methods. RESULTS: We included 100 participants between June 2022 and October 2023. 45 individuals (45 of 100) had a positive Ng result in either the oral rinses (42 of 45, 93%) or the swabs (36 of 45, 80%). Sensitivity was higher for oral rinses than swabs (sensitivity=0.93/0.80, specificity=1.0/1.0, respectively) and agreement between both techniques was good (kappa=0.75, p<0.001). Of the 42 positive oral rinses, 37 remained positive after a minimum of 5 days (88.1%). Using culture, 18 individuals had a positive Ng result in either the oral rinses (8 of 18, 44%) or the swabs (16 of 18, 88%). Most participants found the oral rinse easy or very easy to use and would be willing to use the oral rinse for home-based sampling. CONCLUSION: We detected more oropharyngeal Ng infections via NAAT using oral rinses than swab samples. However, swabs were better than oral rinses for culturing Ng. Oral rinses might allow for home-based self-sampling to detect oropharyngeal Ng.

Doxycycline post-exposure prophylaxis could theoretically select for resistance to various antimicrobials in 19 pathobionts: an in silico analysis.

OBJECTIVES: Doxycycline post exposure prophylaxis (PEP) has been shown to reduce the incidence of bacterial STIs. However, if there is genetic linkage between resistance to tetracycline and other antimicrobials, then it could also select for resistance to these other antimicrobials. We therefore undertook to evaluate if there is an association between the minimum inhibitory concentrations (MICs) of tetracycline and other antimicrobials in 19 clinically important bacterial species. METHODS: Mixed-effects linear regression was used to assess if minocycline MICs were associated with the MICs of eight other antimicrobials (ceftriaxone, ampicillin, oxacillin, vancomycin, erythromycin, levofloxacin, amikacin, and trimethoprim-sulfamethoxazole) in 19 bacterial species in the Antimicrobial Testing Leadership and Surveillance (ATLAS) database. RESULTS: With the notable exception of vancomycin, where no association was found, strong positive associations were typically found between the MICs of minocycline and each of the eight antimicrobials in each of the species assessed. For example, the minocycline MICs of all the Gram-positive species were positively associated with ampicillin, ceftriaxone, oxacillin and erythromycin MICs (all P-values < 0.001). The only exceptions were ampicillin for Streptococcus pyogenes and ceftriaxone for S. dysgalactiae, where no significant associations were found. Similarly in the Gram-negative species, the minocycline MICs of all the species except Haemophilus influenzae and Stenotrophomonas maltophilia were positively associated with the MICs of ceftriaxone, ampicillin, levofloxacin and amikacin (all P-values < 0.001). CONCLUSIONS: There is a theoretical risk that doxycycline PEP could select for resistance not only to tetracyclines but to a range of other antimicrobials in each of the 19 pathobionts assessed.

Estimation of antimicrobial resistance of Mycoplasma genitalium, Belgium, 2022.

BackgroundAntimicrobial resistance (AMR) of Mycoplasma genitalium (MG) is a growing concern worldwide and surveillance is needed. In Belgium, samples are sent to the National Reference Centre of Sexually Transmitted Infections (NRC-STI) on a voluntary basis and representative or robust national AMR data are lacking.AimWe aimed to estimate the occurrence of resistant MG in Belgium.MethodsBetween July and November 2022, frozen remnants of MG-positive samples from 21 Belgian laboratories were analysed at the NRC-STI. Macrolide and fluoroquinolone resistance-associated mutations (RAMs) were assessed using Sanger sequencing of the 23SrRNA and parC gene. Differences in resistance patterns were correlated with surveillance methodology, socio-demographic and behavioural variables via Fisher's exact test and logistic regression analysis.ResultsOf the 244 MG-positive samples received, 232 could be sequenced for macrolide and fluoroquinolone RAMs. Over half of the sequenced samples (55.2%) were resistant to macrolides. All sequenced samples from men who have sex with men (MSM) (24/24) were macrolide-resistant. Fluoroquinolone RAMs were found in 25.9% of the samples and occurrence did not differ between socio-demographic and sexual behaviour characteristics.ConclusionAlthough limited in sample size, our data suggest no additional benefit of testing MG retrieved from MSM for macrolide resistance in Belgium, when making treatment decisions. The lower occurrence of macrolide resistance in other population groups, combined with emergence of fluoroquinolone RAMs support macrolide-resistance testing in these groups. Continued surveillance of resistance in MG in different population groups will be crucial to confirm our findings and to guide national testing and treatment strategies.

Protective effect of microbisporicin (NAI-107) against vancomycin resistant Enterococcus faecium infection in a Galleria mellonella model.

Increasing antimicrobial resistance in Enterococcus faecium necessitates the search for novel treatment agents, such as bacteriocins. In this study, we conducted an in vivo assessment of five bacteriocins, namely Lacticin Z, Lacticin Q, Garvicin KS (ABC), Aureocin A53 and Microbisporicin (NAI-107), against vanB-resistant Enterococcus faecium using a Galleria mellonella model. Our in vitro experiments demonstrated the efficacy of all five bacteriocins against vanB-resistant E. faecium with only NAI-107 demonstrating in vivo efficacy. Notably, NAI-107 exhibited efficacy across a range of tested doses, with the highest efficacy observed at a concentration of 16 µg/mL. Mortality rates in the group treated with 16 µg/mL NAI-107 were lower than those observed in the linezolid-treated group. These findings strongly suggest that NAI-107 holds promise as a potential alternative therapeutic agent for treating infections caused by resistant E. faecium and warrants further investigation.

Lack of Association between Antimicrobial Consumption and Antimicrobial Resistance in a HIV Preexposure Prophylaxis Population: A Cross-Sectional Study.

BACKGROUND: In antibiotic naïve populations, there is a strong association between the use of an antimicrobial and resistance to this antimicrobial. Less evidence is available as to whether this relationship is weakened in populations highly exposed to antimicrobials. Individuals taking HIV preexposure prophylaxis (PrEP) have a high intake of antimicrobials. We previously found that there was no difference in the prevalence of pheno- and genotypic antimicrobial resistance between two groups of PrEP clients who had, and had not, taken antimicrobials in the prior 6 months. Both groups did, however, have a higher prevalence of resistance than a sample of the general population. METHODS: In the current study, we used zero-inflated negative binomial regression models to evaluate if there was an individual level association between the consumption of antimicrobials and 1. the minimum inhibitory susceptibilities of oral Neisseria subflava and 2. the abundance of antimicrobial resistance genes in the oropharynges of these individuals. RESULTS: We found no evidence of an association between the consumption of antimicrobials and the minimum inhibitory susceptibilities of oral Neisseria subflava or the abundance of antimicrobial resistance genes in these individuals. CONCLUSIONS: We conclude that in high-antimicrobial-consumption populations, the association between antimicrobial consumption and resistance may be attenuated. This conclusion would not apply to lower-consumption populations.

Effect of screening for Neisseria gonorrhoeae and Chlamydia trachomatis on incidence of these infections in men who have sex with men and transgender women taking HIV pre-exposure prophylaxis (the Gonoscreen study): results from a randomised, multicentre, controlled trial.

BACKGROUND: Guidelines recommend screening for Neisseria gonorrhoeae and Chlamydia trachomatis at three anatomical sites (urethra, anus, and pharynx) every 3 months (3 × 3) in men who have sex with men (MSM) and transgender women taking HIV pre-exposure prophylaxis (PrEP). We present the first randomised controlled trial to compare the effect of screening versus non-screening for N gonorrhoeae and C trachomatis on the incidence of these infections in MSM and transgender women taking PrEP. METHODS: A multicentre, randomised, controlled trial of 3 × 3 screening for N gonorrhoeae and C trachomatis versus non-screening was done among MSM and transgender women taking PrEP in five HIV reference centers in Belgium. Participants attended the PrEP clinics quarterly for 12 months. N gonorrhoeae and C trachomatis was tested at each visit in both arms, but results were not provided to the non-screening arm, if asymptomatic. The primary outcome was incidence rate of N gonorrhoeae and C trachomatis infections in each arm, assessed in the per-protocol population. Non-inferiority of the non-screening arm was proven if the upper limit of the 95% CI of the incidence rate ratio (IRR) was lower than 1·25. This trial is registered with ClinicalTrials.gov, NCT04269434, and is completed. FINDINGS: Between Sept 21, 2020, and June 4, 2021, 506 participants were randomly assigned to the 3 × 3 screening arm and 508 to the non-screening arm. The overall incidence rate of N gonorrhoeae and C trachomatis was 0·155 cases per 100 person-days (95% CI 0·128-0·186) in the 3 × 3 screening arm and 0·205 (95% CI 0·171-0·246) in the non-screening arm. The incidence rate was significantly higher in the non-screening arm (IRR 1·318, 95% CI 1·068-1·627). Participants in the non-screening arm had a higher incidence of C trachomatis infections and symptomatic C trachomatis infections. There were no significant differences in N gonorrhoeae infections. Participants in the non-screening arm consumed significantly fewer antimicrobial drugs. No serious adverse events were reported. INTERPRETATION: We failed to show that non-screening for N gonorrhoeae and C trachomatis is non-inferior to 3 × 3 screening in MSM and transgender women taking PrEP in Belgium. However, screening was associated with higher antibiotic consumption and had no effect on the incidence of N gonorrhoeae. Further research is needed to assess the benefits and harms of N gonorrhoeae and C trachomatis screening in this population. FUNDING: Belgian Health Care Knowledge Centre.

Gonococcal resistance to zoliflodacin could emerge via transformation from commensal Neisseria species. An in-vitro transformation study.

One of the most promising new treatments for gonorrhoea currently in phase 3 clinical trials is zoliflodacin. Studies have found very little resistance to zoliflodacin in currently circulating N. gonorrhoeae strains, and in-vitro experiments demonstrated that it is difficult to induce resistance. However, zoliflodacin resistance may emerge in commensal Neisseria spp., which could then be transferred to N. gonorrhoeae via transformation. In this study, we investigated this commensal-resistance-pathway hypothesis for zoliflodacin. To induce zoliflodacin resistance, ten wild-type susceptible isolates belonging to 5 Neisseria species were serially passaged for up to 48 h on gonococcal agar plates containing increasing zoliflodacin concentrations. Within 7 to 10 days, all strains except N. lactamica, exhibited MICs of ≥ 4 µg/mL, resulting in MIC increase ranging from 8- to 64-fold. The last passaged strains and their baseline were sequenced. We detected mutations previously reported to cause zoliflodacin resistance in GyrB (D429N and S467N), novel mutations in the quinolone resistance determining region (QRDR) (M464R and T472P) and mutations outside the QRDR at amino acid positions 28 and 29 associated with low level resistance (MIC 2 µg/mL). Genomic DNA from the laboratory evolved zoliflodacin-resistant strains was transformed into the respective baseline wild-type strain, resulting in MICs of ≥ 8 µg/mL in most cases. WGS of transformants with decreased zoliflodacin susceptibility revealed presence of the same zoliflodacin resistance determinants as observed in the donor strains. Two inter-species transformation experiments were conducted to investigate whether zoliflodacin resistance determinants of commensal Neisseria spp. could be acquired by N. gonorrhoeae. N. gonorrhoeae strain WHO P was exposed to (i) pooled genomic DNA from the two resistant N. mucosa strains and (ii) a gyrB amplicon of the resistant N. subflava strain 45/1_8. Transformants of both experiments exhibited an MIC of 2 µg/mL and whole genome analysis revealed uptake of the mutations detected in the donor strains. This is the first in-vitro study to report that zoliflodacin resistance can be induced in commensal Neisseria spp. and subsequently transformed into N. gonorrhoeae.