New treatment options for Neisseria gonorrhoeae in the era of emerging antimicrobial resistance

Antimicrobial Resistance in Gonorrhea

Antimicrobial resistance is a global public health emergency. The World Health Organization recently highlighted the growing number of new sexually transmitted infections such as gonorrhea, syphilis, and Chlamydia, which are resistant to common antibiotics. The phenomenon is also on the rise due to increasing intercontinental travel. Emerging antibiotic-resistant strains of gonorrhea are particularly associated with international spread from Southeast Asian travelers. Infection with Neisseria gonorrhoeae can cause a wide spectrum of associated diseases such as dermatitis, arthritis and septic arthritis, and pelvic inflammatory disease, and can even lead to serious health consequences for the individual. Natural infection confers no immunity, and vaccination is not available currently, although in several countries, it has been reported that the antimeningococcal vaccine may protect against gonorrhea. Implementing all necessary preventive measures is crucial, as well as appropriate and timely diagnostic methods and effective antimicrobial therapeutic treatments in the correct modalities to avoid the increase of forms of gonorrhea that are resistant to common antibiotics and difficult to eradicate.

A systematic review of Neisseria gonorrhoeae drug resistance development in South Africa

In South Africa, basic healthcare centres treat sexually transmitted infections (STIs) using a syndromic approach. In line with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations, a complete study of all randomised controlled trials and surveillance data relevant to N. gonorrhoeae antibiotic resistance was conducted. To discover papers published between 2002 and 2022, searches were undertaken using PubMed, EMBASE and any other relevant databases. This systematic review extracted a total of 463 articles published between 2002 and 2022 from a variety of online research sources. Seven South African provinces were represented in the studies that were assessed. Mpumalanga and the North West Province did not have any studies that described the identification and monitoring of antimicrobial resistance (AMR). This study presents data obtained from a comprehensive analysis of 2140 isolates, in which we examined the presence of one or more antibiotic resistance. Our findings revealed that out of these samples, 1891 isolates exhibited antimicrobial properties; tetracycline was the antimicrobial resistance that was found the most often (30%), followed by ciprofloxacin (19%) and penicillin (17%). The mean of the isolates was 143, the upper 95% mean was 243, and the standard deviation (SD) was 181.6. All microbiological identification and susceptibility testing processes must be standardised and improved so national organisations can monitor AMR. The nation's health community must address all identified areas of concern to avoid AMR.

Ameliorating Gonorrhea: Recent Therapeutic Adaptations and Scope to Improve its Prevailing Condition

BACKGROUND

Gonorrhea is a sexually transmitted infection (STI) caused by the bacteria Neisseria gonorrhoeae. According to recent research, the prevalence of gonorrhea has been increasing in many parts of the world, with some areas reporting high rates of antibiotic resistance. In the United States, the Centers for Disease Control and Prevention (CDC) reported that the number of reported gonorrhea cases increased by 56% between 2015 and 2019. Globally, the World Health Organization (WHO) estimated that there were 87 million new cases of gonorrhea in 2016, with the highest burden of infection in low- and middle-income countries. Research has also shown that gonorrhea is becoming increasingly resistant to conventional antibiotics, increasing the prevalence of gonorrhea. This raises concerns and challenges in disease management.

OBJECTIVES

The present review gives updated insight on the current state of the disease, challenges, and shortcomings of existing approaches along with the modern and alternative direction like vaccine development, its challenges, and scope to confront the existing state of drug resistance and increased rate of incidence. Alternative strategies like immunotherapy and phage therapy along with recent antibiotics researched for the treatment of gonorrhea.

CONCLUSION

The review provides a thorough insight into the current state of the disease and various available methods used currently and recommended by WHO. To overcome disease prevalence, various alternate therapies are coming into the limelight. However, scientists and researchers show a lack of interest in the drug development and research of gonorrhea, due to less commercial scope, lack of funding, and limited scope in the scientific scenario. These hurdles need to be overcome to meet the WHO vision of reducing gonorrhea by 90% by 2030. So, there is a need to optimize the drug therapy (optimizing dosing schedule, and precision monitoring) to reduce the chance of drug resistance. Also, there is a wide scope for drug and therapeutic system development.

Neisseria gonorrhoeae Antimicrobial Resistance: The Future of Antibiotic Therapy

The growing threat of antibiotic-resistant Neisseria gonorrhoeae, which causes gonorrhea, presents a current public health challenge. Over the years, the pathogen has developed resistance to different antibiotics, leaving few effective treatment options. High-level resistance to key drugs, including ceftriaxone, has become a concerning reality. This article primarily focuses on the treatment of gonorrhea and the current clinical trials aimed at providing new antibiotic treatment options. We explore ongoing efforts to assess new antibiotics, including zoliflodacin, and gepotidacin. These drugs offer new effective treatment options, but their rapid availability remains uncertain. We delve into two ongoing clinical trials: one evaluating the efficacy and safety of gepotidacin compared to the standard ceftriaxone-azithromycin combination and the other assessing the non-inferiority of zoliflodacin versus the combination therapy of ceftriaxone-azithromycin. These trials represent crucial steps in the search for alternative treatments for uncomplicated gonorrhea. Notably, gonorrhea has been included in the "WHO Priority Pathogens List for Research and Development of New Antibiotics". In conclusion, the urgent need for innovative treatment strategies is underscored by the rising threat of antibiotic resistance in N. gonorrhoeae; collaboration among researchers, industries, and healthcare authorities is therefore essential.

Gonorrhea prevalence in adults in Brazil: Spectrum-STI trend estimation, 2000-2020

BACKGROUND

Gonorrhea is not a notifiable disease in Brazil, and the national health information system does not collect data on reported cases or infection prevalence.

METHODS

We compiled published data on gonorrhea prevalence in Brazil from cross-sectional surveys and clinical trials between 2000 and 2020. The study entry criteria included a sample size of 50 or more, and Neisseria gonorrhoeae infection detected in urine, urethral, anal, or cervicovaginal specimens using either Nucleic Acid Amplification Test or culture. Gonorrhea prevalence trends between 2000 and 2020 were generated using Spectrum-STI, a statistical trend-fitting model.

RESULTS

Forty-five studies with 59 gonorrhea prevalence data points were identified. Fifty data points were for women and represented 21,815 individuals, eight for men encompassing a total of 4,587 individuals, and one for transgender people comprising 345 individuals. The Spectrum-STI estimate for the prevalence of urogenital infection with gonorrhea in women 15-49 in 2020 was 0.63% (95% confidence interval (CI): 0.13-2.23) and was lower than the 1.05% estimated value for 2000 (95% CI: 0.36-2.79). The corresponding figures for men were 0.70% (95% CI: 0.16-2.44) and 1.14% (95% CI: 0.34-3.15). Anal prevalence estimates could not be generated because of insufficient data (three data points).

CONCLUSIONS

These results suggest that the overall prevalence of genitourinary gonococcal infections in Brazil is less than 1%. Data on gonorrhea prevalence in men and in populations at increased STI vulnerability are limited.

Antimicrobial effects of Medicines for Malaria Venture Pathogen Box compounds on strains of Neisseria gonorrhoeae

Therapeutic options for Neisseria gonorrhoeae are limited due to emerging global resistance. New agents and treatment options to treat patients with susceptible and multi-extensively drug-resistant N. gonorrhoeae is a high priority. This study used an in vitro approach to explore the antimicrobial potential, as well as synergistic effects of Medicine for Malaria Venture (MMV) Pathogen Box compounds against ATCC and clinical N. gonorrhoeae strains. Microbroth dilution assay was used to determine pathogen-specific minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the Pathogen Box compounds against susceptible and resistant N. gonorrhoeae strains, with modification, by adding PrestoBlue HS Cell Viability Reagent. A checkerboard assay was used to determine synergy between the active compounds and in conjunction with ceftriaxone. Time-kill kinetics was performed to determine if the compounds were either bactericidal or bacteriostatic. The Pathogen Box compounds: MMV676501, MMV002817, MMV688327, MMV688508, MMV024937, MMV687798 (levofloxacin), MMV021013, and MMV688978 (auranofin) showed potent activity against resistant strains of N. gonorrhoeae at an MIC and MBC of ≤10 µM. Besides the eight compounds, MMV676388 and MMV272144 were active against susceptible N. gonorrhoeae strains, also at MIC and MBC of ≤10 µM. All the compounds were bactericidal and were either synergistic or additive with fractional inhibitory concentration index ranging between 0.40 and 1.8. The study identified novel Pathogen Box compounds with potent activity against N. gonorrhoeae strains and has the potential to be further investigated as primary or adjunctive therapy to treat gonococcal infections.

Antimicrobial susceptibility assays for Neisseria gonorrhoeae: a proof-of-principle population-based retrospective analysis

BACKGROUND

Neisseria gonorrhoeae treatment guided by molecular antimicrobial susceptibility assays could improve treatment options and antimicrobial stewardship; however, few commercial assays are available. We aimed to investigate antimicrobial susceptibility of N gonorrhoeae isolates in New South Wales, Australia, and estimate the potential usefulness of hypothetical combinations of rapid molecular antimicrobial susceptibility assays.

METHODS

In this proof-of-principle, population-based, retrospective analysis, we assessed N gonorrhoeae susceptibility data for ceftriaxone, azithromycin, ciprofloxacin, and penicillin. Isolates were previously collected as part of the Australian Gonococcal Surveillance Programme between Jan 1, 2008, and Dec 31, 2019. All cultured N gonorrhoeae isolates with susceptibility data to all four antimicrobials were included. However, only one isolate was included if several isolates originated from the same individual within 13 days of the previous isolate originating from that individual, and there were less than two standard double-dilution minimum inhibitory concentrations between the isolates. We assessed the use of different combinations of hypothetical antimicrobial susceptibility assays and treatment combinations in terms of their ability to minimise overall ceftriaxone use, and use specifically in isolates with decreased susceptibility to ceftriaxone, compared with standard non-assay-guided empirical ceftriaxone treatment.

FINDINGS

We included 23 089 N gonorrhoeae isolates. The prevalence of antimicrobial sensitivity fluctuated significantly during the study. Isolates with decreased susceptibility to ceftriaxone were more likely to be resistant to one or more antimicrobials than isolates without decreased susceptibility (782 [98·6%] of 793 vs 10 661 [47·8%] of 22 296), particularly ciprofloxacin (p<0·0001) and penicillin (p<0·0001). Compared with empirical ceftriaxone treatment, we estimated that strategies based on the use of hypothetical antimicrobial susceptibility would reduce ceftriaxone use (p<0·0001). However, because of co-resistance, most assay-directed treatment strategies, including those involving use of assays for two antibiotics, would result in only moderate reductions in ceftriaxone use among isolates with decreased susceptibility to ceftriaxone.

INTERPRETATION

Individualised treatment guided by molecular antimicrobial susceptibility diagnostics could help to reduce overall ceftriaxone use in gonorrhoea. However, the use of these assays needs to be informed by the non-random nature of co-resistance among circulating N gonorrhoeae strains.

FUNDING

Australian Government and Queensland Government.

Penicillin-Binding Protein Occupancy Dataset for 18 β-Lactams and 4 β-Lactamase Inhibitors in Neisseria gonorrhoeae

The lack of effective first-line antibiotic treatments against Neisseria gonorrhoeae, and the worldwide dissemination of resistant strains, are the main drivers of a worsening global health crisis. β-lactam antibiotics have been the backbone of therapeutic armamentarium against gonococci. However, we are lacking critical insights to design rationally optimized therapies. In the present work, we generated the first PBP-binding data set on 18 currently available and clinically relevant β-lactams and 4 β-lactamase inhibitors in two N. gonorrhoeae ATCC type collection strains, 19424 and 49226 (PBP2 type XXII and A39T change in mtrR). PBP binding (IC50) was determined via the Bocillin FL binding assay in isolated membrane preparations. Three clusters of differential PBP IC50s were identified and were mostly consistent across both strains, but with quantitative differences. Carbapenems were coselective for PBP2 and PBP3 (0.01 to 0.03 mg/L). Third- and fourth-generation cephalosporins cefixime, cefotaxime, ceftazidime, cefepime, and ceftriaxone showed the lowest IC50 values for PBP2 (0.01 mg/L), whereas cefoxitin, ceftaroline, and ceftolozane required higher concentrations (0.04 to >2 mg/L). Aztreonam was selective for PBP2 in both strains (0.03 to 0.07 mg/L); amdinocillin bound this PBP at higher concentrations (1.33 to 2.94 mg/L). Penicillins specifically targeted PBP2 in strain ATCC 19424 (0.02 to 0.19 mg/L) and showed limited inhibition in strain ATCC 49226 (0.01 to >2 mg/L). Preferential PBP2 binding was observed by β-lactam-based β-lactamase inhibitors sulbactam and tazobactam (1.07 to 6.02 mg/L); meanwhile, diazabicyclooctane inhibitors relebactam and avibactam were selective for PBP3 (1.27 to 5.40 mg/L). This data set will set the bar for future studies that will help the rational use and translational development of antibiotics against multidrug-resistant (MDR) N. gonorrhoeae. IMPORTANCE The manuscript represents the first N. gonorrhoeae PBP-binding data set for 22 chemically different drugs in two type strains with different genetic background. We have identified three clusters of drugs according to their PBP binding IC50s and highlighted the binding differences across the two strains studied. With the currently available genomic information and the PBP-binding data, we have been able to correlate the target attainment differences and the mutations that affect the drug uptake with the MIC changes. The results of the current work will allow us to develop molecular tools of great practical use for the study and the design of new rationally designed therapies capable of combating the growing MDR gonococci threat.

Reverse vaccinology approaches to introduce promising immunogenic and drug targets against antibiotic-resistant Neisseria gonorrhoeae: Thinking outside the box in current prevention and treatment

Gonorrhea is an urgent antimicrobial resistance threat and its therapeutic options are continuously getting restricted. Moreover, no vaccine has been approved against it so far. Hence, the present study aimed to introduce novel immunogenic and drug targets against antibiotic-resistant Neisseria gonorrhoeae strains. In the first step, the core proteins of 79 complete genomes of N. gonorrhoeae were retrieved. Next, the surface-exposed proteins were evaluated from different aspects such as antigenicity, allergenicity, conservancy, and B-cell and T-cell epitopes to introduce promising immunogenic candidates. Then, the interactions with human Toll-like receptors (TLR-1, 2, and 4), and immunoreactivity to elicit humoral and cellular immune responses were simulated. On the other hand, to identify novel broad-spectrum drug targets, the cytoplasmic and essential proteins were detected. Then, the N. gonorrhoeae metabolome-specific proteins were compared to the drug targets of the DrugBank, and novel drug targets were retrieved. Finally, the protein data bank (PDB) file availability and prevalence among the ESKAPE group and common sexually transmitted infection (STI) agents were assessed. Our analyses resulted in the recognition of ten novel and putative immunogenic targets including murein transglycosylase A, PBP1A, Opa, NlpD, Azurin, MtrE, RmpM, LptD, NspA, and TamA. Moreover, four potential and broad-spectrum drug targets were identified including UMP kinase, GlyQ, HU family DNA-binding protein, and IF-1. Some of the shortlisted immunogenic and drug targets have confirmed roles in adhesion, immune evasion, and antibiotic resistance that can induce bactericidal antibodies. Other immunogenic and drug targets might be associated with the virulence of N. gonorrhoeae as well. Thus, further experimental studies and site-directed mutations are recommended to investigate the role of potential vaccine and drug targets in the pathogenesis of N. gonorrhoeae.

Systematic Review and Meta-Analysis to Estimate the Treatment Effect and Inform a Noninferiority Margin for a Phase 3 Noninferiority Trial in Uncomplicated Urogenital Gonorrhea

BACKGROUND

Active-controlled noninferiority studies are used to investigate novel agents for uncomplicated urogenital gonorrhea (uUGC) as placebo-controlled trials are unethical. A systematic literature review and meta-analysis were conducted to estimate the ceftriaxone and proxy-for-placebo microbiological treatment effect and determine an appropriate noninferiority margin for phase 3 trials.

METHODS

Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. To account for interstudy variability, a weighted, noniterative random-effects model was fitted using "R" software to estimate the microbiological response rate and 95% confidence intervals (CIs) for ceftriaxone and proxy-for-placebo (treatment with an antibiotic the isolate was subsequently confirmed resistant to, or spontaneous resolution without treatment). I2 , τ2 , and P values were computed and included in the meta-analysis forest plot.

RESULTS

Seventeen studies were included in the meta-analysis; 14 reported ceftriaxone response in micro-intent-to-treat and microbiologically evaluable populations, and 3 reported proxy-for-placebo treatment response in uUGC (microbiologically evaluable population only). Microbiological treatment effect was estimated by subtracting the upper end of the CI for placebo from the lower end of the CI for ceftriaxone. Overall microbiological response was 98% (95% CI, 97-99) for ceftriaxone and 44% (95% CI, 34-54) for proxy-for-placebo, resulting in a microbiological treatment effect of 43%. A noninferiority margin of 15% preserved 65% of the ceftriaxone treatment effect, exceeding the 50% recommended per US Food and Drug Administration guidance for noninferiority studies.

CONCLUSIONS

Results of this systematic literature review and meta-analysis could help inform the design, conduct, and analysis of future clinical studies in uUGC.

A Novel Oral GyrB/ParE Dual Binding Inhibitor Effective against Multidrug-Resistant Neisseria gonorrhoeae and Other High-Threat Pathogens

Drug-resistant Neisseria gonorrhoeae is a serious global health concern. New drugs are needed that can overcome existing drug resistance and limit the development of new resistances. Here, we describe the small molecule tricyclic pyrimidoindole JSF-2414 [8-(6-fluoro-8-(methylamino)-2-((2-methylpyrimidin-5-yl)oxy)-9H-pyrimido[4,5-b]indol-4-yl)-2-oxa-8-azaspiro[4.5]decan-3-yl)methanol], which was developed to target both ATP-binding regions of DNA gyrase (GyrB) and topoisomerase (ParE). JSF-2414 displays potent activity against N. gonorrhoeae, including drug-resistant strains. A phosphate pro-drug, JSF-2659, was developed to facilitate oral dosing. In two different animal models of Neisseria gonorrhoeae vaginal infection, JSF-2659 was highly efficacious in reducing microbial burdens to the limit of detection. The parent molecule also showed potent in vitro activity against high-threat Gram-positive organisms, and JSF-2659 was shown in a deep tissue model of vancomycin-resistant Staphylococcus aureus (VRSA) and a model of Clostridioides difficile-induced colitis to be highly efficacious and protective. JSF-2659 is a novel preclinical drug candidate against high-threat multidrug resistant organisms with low potential to develop new resistance.

Limitations of Phage Therapy and Corresponding Optimization Strategies: A Review

Bacterial infectious diseases cause serious harm to human health. At present, antibiotics are the main drugs used in the treatment of bacterial infectious diseases, but the abuse of antibiotics has led to the rapid increase in drug-resistant bacteria and to the inability to effectively control infections. Bacteriophages are a kind of virus that infects bacteria and archaea, adopting bacteria as their hosts. The use of bacteriophages as antimicrobial agents in the treatment of bacterial diseases is an alternative to antibiotics. At present, phage therapy (PT) has been used in various fields and has provided a new technology for addressing diseases caused by bacterial infections in humans, animals, and plants. PT uses bacteriophages to infect pathogenic bacteria so to stop bacterial infections and treat and prevent related diseases. However, PT has several limitations, due to a narrow host range, the lysogenic phenomenon, the lack of relevant policies, and the lack of pharmacokinetic data. The development of reasonable strategies to overcome these limitations is essential for the further development of this technology. This review article described the current applications and limitations of PT and summarizes the existing solutions for these limitations. This information will be useful for clinicians, people working in agriculture and industry, and basic researchers.

Modelling response strategies for controlling gonorrhoea outbreaks in men who have sex with men in Australia

The ability to treat gonorrhoea with current first-line drugs is threatened by the global spread of extensively drug resistant (XDR) Neisseria gonorrhoeae (NG) strains. In Australia, urban transmission is high among men who have sex with men (MSM) and importation of an XDR NG strain in this population could result in an epidemic that would be difficult and costly to control. An individual-based, anatomical site-specific mathematical model of NG transmission among Australian MSM was developed and used to evaluate the potential for elimination of an imported NG strain under a range of case-based and population-based test-and-treat strategies. When initiated upon detection of the imported strain, these strategies enhance the probability of elimination and reduce the outbreak size compared with current practice (current testing levels and no contact tracing). The most effective strategies combine testing targeted at regular and casual partners with increased rates of population testing. However, even with the most effective strategies, outbreaks can persist for up to 2 years post-detection. Our simulations suggest that local elimination of imported NG strains can be achieved with high probability using combined case-based and population-based test-and-treat strategies. These strategies may be an effective means of preserving current treatments in the event of wider XDR NG emergence.

In most high-income settings, gonorrhoea is endemic among men who have sex with men (MSM). While gonorrhoea remains readily treatable with antibiotics, there are major concerns about the threat of antimicrobial resistance arising from recent reports of treatment failure with first-line therapy and limited remaining treatment options. Here we investigated the potential for test-and-treat response strategies to eliminate such strains before their prevalence reaches a level requiring a shift to new first line therapies. Rather than directly consider resistance, we explore the mitigating effect of various test-and-treat measures on outbreaks of a generic imported strain which remains treatable. This is done within the framework of a realistic mathematical model of gonorrhoea spread in an MSM community that captures cases, anatomical sites of infection and sexual contacts at an individual level, calibrated to relevant Australian epidemiological data. The results indicate that strategies such as partner testing and treatment in combination with elevated asymptomatic community testing are highly effective in mitigating outbreaks but can take up to 2 years to achieve elimination. As there are currently no clear alternative drugs of proven efficacy and safety to replace ceftriaxone in first-line therapy, these promising results suggest potential for use of these outbreak response strategies to preserve current treatment recommendations.

Antimicrobial Susceptibility of Ertapenem in Neisseria gonorrhoeae Isolates Collected Within the China Gonococcal Resistance Surveillance Programme (China-GRSP) 2018

Purpose

This study aimed to determine the minimum inhibitory concentrations (MICs) of ertapenem on Neisseria gonorrhoeae collected from eight Chinese provinces in 2018.

Methods

The MICs of ertapenem on 503 Neisseria gonorrhoeae isolates (415 isolates selected randomly and 88 isolates selected with preference) were measured using the agar dilution method. For comparison, the MICs of ceftriaxone and azithromycin were detected.

Results

Among 415 randomly selected isolates, the MIC range for ertapenem was from ≤0.008 mg/L to 0.5 mg/L. The corresponding MIC₅₀ and MIC₉₀ were 0.06 and 0.125 mg/L, respectively. Twelve of 415 isolates (2.9%) exhibited MIC values ≥0.25 mg/L, and only one isolate (0.2%) had a MIC of 0.5 mg/L. By comparing all 503 tested isolates, a correlation of r = 0.487 (P <0.001) between ertapenem and ceftriaxone MIC was observed, and the correlation between MICs of ertapenem and azithromycin was low (r = -0.12, P = 0.007). In 24 ceftriaxone-decreased susceptibility isolates, four isolates (16.7%) showed a MIC ≥0.25 mg/L for ertapenem. In 85 azithromycin resistant isolates, three isolates (3.5%) showed a MIC ≥0.25 mg/L for ertapenem.

Conclusion

The in vitro results suggest that ertapenem has satisfactory susceptibility in isolates collected from eight provinces in China; hence, it might be a promising treatment option for resistant gonococcal infections.

Structure-Activity Relationship Studies of Acetazolamide-Based Carbonic Anhydrase Inhibitors with Activity against Neisseria gonorrhoeae

Neisseria gonorrhoeae is an urgent threat to public health in the United States and around the world. Many of the current classes of antibiotics to treat N. gonorrhoeae infection are quickly becoming obsolete due to increased rates of resistance. Thus, there is a critical need for alternative antimicrobial targets and new chemical entities. Our team has repurposed the FDA-approved carbonic anhydrase inhibitor scaffold of acetazolamide to target N. gonorrhoeae and the bacteria's essential carbonic anhydrase, NgCA. This study established both structure-activity and structure-property relationships that contribute to both antimicrobial activity and NgCA activity. This ultimately led to molecules 20 and 23, which displayed minimum inhibitory concentration values as low as 0.25 μg/mL equating to an 8- to 16-fold improvement in antigonococcal activity compared to acetazolamide. These analogues were determined to be bacteriostatic against the pathogen and likely on-target against NgCA. Additionally, they did not exhibit any detrimental effects in cellular toxicity assays against both a human endocervical (End1/E6E7) cell line or colorectal adenocarcinoma cell line (Caco-2) at concentrations up to 128 μg/mL. Taken together, this study presents a class of antigonococcal agents with the potential to be advanced for further evaluation in N. gonorrhoeae infection models.

Efficacy of Antigonococcal CMP-Nonulosonate Therapeutics Require Cathelicidins

Novel therapies to counteract multidrug-resistant gonorrhea are urgently needed. A unique gonococcal immune evasion strategy involves capping of lipooligosaccharide (LOS) with sialic acid by gonococcal sialyltransferase (Lst), utilizing host-derived CMP-sialic acid (CMP-Neu5Ac in humans). LOS sialylation renders gonococci resistant to complement and cationic peptides, and down-regulates the inflammatory response by engaging siglecs. CMP-sialic acid analogs (CMP-nonulosonates [CMP-NulOs]) such as CMP-Leg5,7Ac2 and CMP-Kdn are also utilized by Lst. Incorporation of these NulO analogs into LOS maintains gonococci susceptible to complement. Intravaginal administration of CMP-Kdn or CMP-Leg5,7Ac2 attenuates gonococcal colonization of mouse vaginas. Here, we identify a key mechanism of action for the efficacy of CMP-NulOs. Surprisingly, CMP-NulOs remained effective in complement C1q-/- and C3-/- mice. LOS Neu5Ac, but not Leg5,7Ac2 or Kdn, conferred resistance to the cathelicidins LL-37 (human) and mouse cathelicidin-related antimicrobial peptide in vitro. CMP-NulOs were ineffective in Camp-/- mice, revealing that cathelicidins largely mediate the efficacy of therapeutic CMP-NulOs.

Sexually transmitted infections (STIs) and its changing scenario: A scoping review

Sexually transmitted infections (STIs) and reproductive tract infections (RTIs) have existed worldwide since ancient time, causing significant morbidity and mortality. To maintain healthy sexual and reproductive life, it is highly essential to prevent STIs, RTIs and related illnesses. STIs are transmitted by swapping body fluids among people during sexual intercourse. The etiological agents for STIs are bacteria, virus and parasites for most cases, but proportions by different aetiology are changing. Various studies have shown that STIs are increasing, and its primary aetiology is changing worldwide. That should be considered seriously and needs necessary actions. Several factors related to hosts and disease-causing agents have identified to influence STIs' current strategies in the prevention and control program. The present assessment attempts to review the history, changing aetiology and antimicrobial resistance in STIs. This review has also highlighted the prevalence of STIs at the global level and their past and present trends in India, emphasising its future challenges and perspectives for making effective public health policies to prevent and control STIs.

Is gentamicin a viable therapeutic option for treating resistant Neisseria gonorrhoeae in New South Wales?

Abstract

The key issues with Neisseria gonorrhoeae infections, in Australia and elsewhere, are coincident increases in disease rates and in antimicrobial resistance (AMR), although these factors have not been shown to be correlated. Despite advances in diagnosis, control of this disease remains elusive, and incidence in Australia continues to increase. Of the Australian jurisdictions, New South Wales (NSW) has the highest N. gonorrhoeae notifications, and over the five-year period 2015-2019, notifications in NSW have increased above the national average (by 116% versus 85%, respectively). Gonococcal disease control is reliant on effective antibiotic regimens. However, escalating AMR in N. gonorrhoeae is a global health priority, as the collateral injury of untreated infections has substantive impacts on sexual and newborn health. Currently, our first-line therapy for gonorrhoea is also our last line, with no ideal alternative identified. Despite some limitations, gentamicin is licensed and readily available in Australia, and is proposed for treatment of resistant N. gonorrhoeae in national guidelines; however, supportive published microbiological data are lacking. Analysis of gonococcal resistance patterns within Australia for the period 1991-2019, including 35,000 clinical isolates from NSW, illustrates the establishment and spread of population-level resistance to all contemporaneous therapies. An analysis of gentamicin susceptibility on 2,768 N. gonorrhoeae clinical isolates from NSW, for the period 2015-2020, demonstrates that the median minimum inhibitory concentration (MIC) for gentamicin in NSW has remained low, at 4.0 mg/L, and resistance was not detected in any isolate. There has been no demonstration of MIC drift over time (p = 0.91, Kruskal-Wallis test), nor differences in MIC distributions according to patients' sex or site of specimen collection. This is the first large-scale evaluation of gentamicin susceptibility in N. gonorrhoeae in Australia. No gentamicin resistance was detected in clinical isolates, 2015-2020, hence this is likely to be an available treatment option for resistant gonococcal infections in NSW.

Antimicrobial Resistance of Neisseria gonorrhoeae Isolates from High-Risk Men in Johannesburg, South Africa

Neisseria gonorrhoeae antimicrobial drug resistance has emerged worldwide; however, the situation in sub-Saharan Africa is not well documented. We investigated the molecular epidemiology and occurrence of antimicrobial resistance in Neisseria gonorrhoeae infections in two core transmission groups of men in Johannesburg, South Africa. We recruited men who have sex with men (MSM) presenting with urethral discharge and men with recurrent episodes of urethral discharge. Molecular testing and culture for N. gonorrhoeae were performed, followed by antimicrobial susceptibility testing. Whole-genome sequencing (WGS) was used to identify resistance-conferring mutations and to determine the genetic relatedness of the isolates. In all, 51 men were recruited; 42 (82%) had N. gonorrhoeae infections. Most gonococcal isolates were resistant to ciprofloxacin (78%) and tetracycline (74%); 33% were penicillin resistant. All gonococcal isolates were susceptible to cephalosporins and spectinomycin. Azithromycin resistance was observed in 4 (15%) isolates (epidemiological cutoff), all with mutations in the mtrR promoter region. Most of the isolates (19/27) harbored the gonococcal genetic island, which is associated with antimicrobial resistance. WGS revealed a diverse epidemic with mostly novel NG-STAR (70%) and NG-MAST (70%) sequence types. Thus, we demonstrate a high prevalence of antimicrobial resistance in Neisseria gonorrhoeae strains obtained from high-risk men in South Africa. The introduction of diagnostics and scale-up of surveillance are warranted to prevent the emergence of multidrug-resistant infections.

Gonorrhea in a Tertiary Care Portuguese Hospital: A 10-year Retrospective Study of the Evolution of Cases and Drug Resistance of the Isolates

BACKGROUND

Sexually Transmitted Infections remain a major public health concern worldwide. Although traditionally considered treatable, the emergence of Neisseria gonorrhoeae resistance to antimicrobials is currently a serious problem. The goal of this study was to evaluate the incidence and trends of antimicrobial resistance over the last 10 years in N. gonorrhoeae isolates from a Portuguese Centre.

METHODS

Laboratorial confirmed N. gonorrhoeae infections diagnosed between 2009 and 2018 were evaluated. Susceptibilities to penicillin, tetracycline, ciprofloxacin, azithromycin and cefotaxime were studied, along with demographic and clinical characteristics.

RESULTS

From 2009 to 2018, 440 cases of N. gonorrhoeae infection were diagnosed in our center, with a significant yearly increase (p<0.05). Most cases occurred in males (97.9%), with a median age of 25 years. In 88.7% of the cases, treatment with ceftriaxone plus azithromycin was used. Resistances to penicillin, tetracycline and ciprofloxacin remained high throughout the study period.

CONCLUSIONS

Antimicrobial resistance of N. gonorrhoeae appeared shortly after the introduction of antimicrobials. To combat this problem, improved surveillance and more studies combining susceptibility and epidemiological data are needed. In our population, N. gonorrhoeae remains highly susceptible to the antibiotics currently recommended for its treatment, whereas ciprofloxacin, azithromycin (in monotherapy) and penicillin should be avoided as empirical treatment.

Gonorrhoea: tackling the global epidemic in the era of rising antimicrobial resistance

This Special Issue of Sexual Health aims to collate the latest evidence base focussed on understanding the current epidemic and transmission of gonorrhoea, choice of treatment, molecular epidemiology application, concerns about antimicrobial resistance and alternative prevention and control for gonorrhoea.

Mycoplasma genitalium coinfection in men with symptomatic gonococcal urethritis

OBJECTIVES

International guidelines recommend Mycoplasma genitalium testing, preferably using an assay to detect macrolide resistance-associated mutations, for men presenting with non-gonococcal urethritis, but there is no specific guidance on such testing for men with gonococcal urethritis.

METHODS

This study aimed to estimate the proportion of men with gonococcal urethritis who have coinfection with M. genitalium through a retrospective analysis of cases of symptomatic urethral gonorrhoea at Western Sydney Sexual Health Centre in 2017 and 2018.

RESULTS

Fourteen of 184 (7.6%, 95% CI 3.7 to 11.5) men with gonococcal urethritis had M. genitalium detected in the urine at the time of presentation. No demographic or behavioural factors predicted M. genitalium coinfection. Coinfection with urethral Chlamydia trachomatis was detected in 29 of 184 (15.8%, 95% CI 10.5 to 21.1). All five men with macrolide-resistant M. genitalium detected returned for treatment with moxifloxacin at a median of 8 days (range 5-16 days) after presentation and treatment of gonorrhoea; three of five were documented to remain symptomatic at this visit.

CONCLUSION

Although M. genitalium coinfection is less common than chlamydia among men with symptomatic gonococcal urethritis, M. genitalium testing, using an assay to detect macrolide resistance, will potentially reduce symptom duration particularly for men with macrolide-resistant infections, but may not be justifiable on cost-benefit analysis.

The frontiers of addressing antibiotic resistance in Neisseria gonorrhoeae

The sexually transmitted infection gonorrhea, caused by the Gram-negative bacterium Neisseria gonorrhoeae, can cause urethritis, cervicitis, and systemic disease, among other manifestations. N. gonorrhoeae has rapidly rising incidence along with increasing levels of antibiotic resistance to a broad range of drugs including first-line treatments. The rise in resistance has led to fears of untreatable gonorrhea causing substantial disease globally. In this review, we will describe multiple approaches being undertaken to slow and control this spread of resistance. First, a number of old drugs have been repurposed and new drugs are being developed with activity against Neisseria gonorrhoeae. Second, vaccine development, long an important goal, is advancing. Third, new diagnostics promise rapid detection of antibiotic resistance and a shift from empiric to tailored treatment. The deployment of these new tools for addressing the challenge of antibiotic resistance will require careful consideration to provide optimal care for all patients while extending the lifespan of treatment regimens.

Therapeutic CMP-Nonulosonates against Multidrug-Resistant Neisseria gonorrhoeae

Neisseria gonorrhoeae deploys a unique immune evasion strategy wherein the lacto-N-neotetraose termini of lipooligosaccharide (LOS) are "capped" by a surface LOS sialyltransferase (Lst), using extracellular host-derived CMP-sialic acid (CMP-Neu5Ac in humans). LOS sialylation enhances complement resistance by recruiting factor H (FH; alternative complement pathway inhibitor) and also by limiting classical pathway activation. Sialylated LOS also engages inhibitory Siglecs on host leukocytes, dampening innate immunity. Previously, we showed that analogues of CMP-sialic acids (CMP-nonulosonates [CMP-NulOs]), such as CMP-Leg5,7Ac₂ and CMP-Neu5Ac9N₃, are also substrates for Lst. Incorporation of Leg5,7Ac₂ and Neu5Ac9N₃ into LOS results in N. gonorrhoeae being fully serum sensitive. Importantly, intravaginal administration of CMP-Leg5,7Ac₂ attenuated N. gonorrhoeae colonization of mouse vaginas. In this study, we characterize and develop additional candidate therapeutic CMP-NulOs. CMP-ketodeoxynonulosonate (CMP-Kdn) and CMP-Kdn7N₃, but not CMP-Neu4,5Ac₂, were substrates for Lst, further elucidating gonococcal Lst specificity. Lacto-N-neotetraose LOS capped with Kdn and Kdn7N₃ bound FH to levels ∼60% of that seen with Neu5Ac and enabled gonococci to resist low (3.3%) but not higher (10%) concentrations of human complement. CMP-Kdn, CMP-Neu5Ac9N₃, and CMP-Leg5,7Ac₂ administered intravaginally (10 μg/d) to N. gonorrhoeae-colonized mice were equally efficacious. Of the three CMP-NulOs above, CMP-Leg5,7Ac₂ was the most pH and temperature stable. In addition, Leg5,7Ac₂-fed human cells did not display this NulO on their surface. Moreover, CMP-Leg5,7Ac₂ was efficacious against several multidrug-resistant gonococci in mice with a humanized sialome (Cmah^-/- mice) or humanized complement system (FH/C4b-binding protein transgenic mice). CMP-Leg5,7Ac₂ and CMP-Kdn remain viable leads as topical preventive/therapeutic agents against the global threat of multidrug-resistant N. gonorrhoeae.

Antimicrobial resistance in sexually transmitted infections

RATIONALE FOR REVIEW

International travel facilitates the spread of drug-resistant infections, including sexually transmitted infections (STIs). In 2016, the World Health Organization highlighted the global burden of 'curable' STIs, estimating 376 million new infections of gonorrhoea, chlamydia, syphilis and trichomoniasis annually, with considerable geographic variation in both the burden of disease and prevalence of resistance. Travelers' risk of contracting and transmitting drug-resistant STIs depends in part on their geographic exposure. In this review, we describe the epidemiology of antimicrobial resistance (AMR) and the management of these four common STIs and Mycoplasma genitalium, an increasingly recognized cause of non-gonococcal urethritis.

KEY FINDINGS

Multi-drug and extensively drug resistant gonorrhoea strains have been associated with international spread, particularly in travelers returning from Southeast Asia. Chlamydia is the most common bacterial STI worldwide. Although in vitro resistance has been reported, surveillance data suggest that clinically significant resistance to macrolides and tetracyclines is rare. Macrolide resistance in syphilis is now endemic in much of the world but there is no documented penicillin resistance, which remains first-line therapy. Trichomoniasis is the most common non-viral STI worldwide. Although clinical failure after treatment occurs, resistance to metronidazole is thought to be uncommon. Mycoplasma genitalium exhibits intrinsic resistance to many antibiotics, and the prevalence of resistance to both first- and second-line regimens (macrolides and fluoroquinolones) is increasing worldwide, with limited alternative therapeutic options.

RECOMMENDATIONS

International travelers are at risk for acquiring resistant STIs with limited therapeutic options. Improved diagnostics are urgently needed to improve AMR surveillance and the management of infected patients. As no vaccinations are currently available for these STIs, and pre-exposure prophylaxis is an area of active study with limited data, condom use is critical for prevention. Travel medicine providers should incorporate STI risk reduction counselling, with an emphasis on condom use, into the routine pre-travel consultation.

World Health Organization Global Gonococcal Antimicrobial Surveillance Program (WHO GASP): review of new data and evidence to inform international collaborative actions and research efforts

Antimicrobial resistance (AMR) in Neisseria gonorrhoeae is a serious public health problem, compromising the management and control of gonorrhoea globally. Resistance in N. gonorrhoeae to ceftriaxone, the last option for first-line empirical monotherapy of gonorrhoea, has been reported from many countries globally, and sporadic failures to cure especially pharyngeal gonorrhoea with ceftriaxone monotherapy and dual antimicrobial therapies (ceftriaxone plus azithromycin or doxycycline) have been confirmed in several countries. In 2018, the first gonococcal isolates with ceftriaxone resistance plus high-level azithromycin resistance were identified in England and Australia. The World Health Organization (WHO) Global Gonococcal Antimicrobial Surveillance Program (GASP) is essential to monitor AMR trends, identify emerging AMR and provide evidence for refinements of treatment guidelines and public health policy globally. Herein we describe the WHO GASP data from 67 countries in 2015-16, confirmed gonorrhoea treatment failures with ceftriaxone with or without azithromycin or doxycycline, and international collaborative actions and research efforts essential for the effective management and control of gonorrhoea. In most countries, resistance to ciprofloxacin is exceedingly high, azithromycin resistance is present and decreased susceptibility or resistance to ceftriaxone has emerged. Enhanced global collaborative actions are crucial for the control of gonorrhoea, including improved prevention, early diagnosis, treatment of index patient and partner (including test-of-cure), improved and expanded AMR surveillance (including surveillance of antimicrobial use and treatment failures), increased knowledge of correct antimicrobial use and the pharmacokinetics and pharmacodynamics of antimicrobials and effective drug regulations and prescription policies (including antimicrobial stewardship). Ultimately, rapid, accurate and affordable point-of-care diagnostic tests (ideally also predicting AMR and/or susceptibility), new therapeutic antimicrobials and, the only sustainable solution, gonococcal vaccine(s) are imperative.