Stemming the tide of drug-resistant Neisseria gonorrhoeae: the need for an individualized approach to treatment

Development of Cas13a-based assays for Neisseria gonorrhoeae detection and gyrase A determination

Neisseria gonorrhoeae is one of the most common bacterial sexually transmitted infections. The emergence of antimicrobial-resistant N. gonorrhoeae is an urgent public health threat. Currently, the diagnosis of N. gonorrhoeae infection requires expensive laboratory infrastructure, while antimicrobial susceptibility determination requires bacterial culture, both of which are infeasible in low-resource areas where the prevalence of infection is highest. Recent advances in molecular diagnostics, such as specific high-sensitivity enzymatic reporter unlocking (SHERLOCK) using CRISPR-Cas13a and isothermal amplification, have the potential to provide low-cost detection of pathogen and antimicrobial resistance. We designed and optimized RNA guides and primer sets for SHERLOCK assays capable of detecting N. gonorrhoeae via the porA gene and of predicting ciprofloxacin susceptibility via a single mutation in the gyrase A (gyrA) gene. We evaluated their performance using both synthetic DNA and purified N. gonorrhoeae isolates. For porA, we created both a fluorescence-based assay and lateral flow assay using a biotinylated fluorescein reporter. Both methods demonstrated sensitive detection of 14 N. gonorrhoeae isolates and no cross-reactivity with 3 non-gonococcal Neisseria isolates. For gyrA, we created a fluorescence-based assay that correctly distinguished between 20 purified N. gonorrhoeae isolates with phenotypic ciprofloxacin resistance and 3 with phenotypic susceptibility. We confirmed the gyrA genotype predictions from the fluorescence-based assay with DNA sequencing, which showed 100% concordance for the isolates studied. We report the development of Cas13a-based SHERLOCK assays that detect N. gonorrhoeae and differentiate ciprofloxacin-resistant isolates from ciprofloxacin-susceptible isolates. IMPORTANCE Neisseria gonorrhoeae, the cause of gonorrhea, disproportionately affects resource-limited settings. Such areas, however, lack the technical capabilities for diagnosing the infection. The consequences of poor or absent diagnostics include increased disease morbidity, which, for gonorrhea, includes an increased risk for HIV infection, infertility, and neonatal blindness, as well as an overuse of antibiotics that contributes to the emergence of antibiotic resistance. We used a novel CRISPR-based technology to develop a rapid test that does not require laboratory infrastructure for both diagnosing gonorrhea and predicting whether ciprofloxacin can be used in its treatment, a one-time oral pill. With further development, that diagnostic test may be of use in low-resource settings.

Chlamydial and Gonococcal Genital Infections: A Narrative Review

Sexually transmitted infections (STIs) constitute one of the leading causes of disease burden worldwide, leading to considerable morbidity, mortality, health expenditures, and stigma. Of note are the most common bacterial STIs, chlamydial and gonococcal infections, whose etiological agents are Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG), respectively. Despite being usually asymptomatic, in some cases these infections can be associated with long-term severe complications, such as pelvic inflammatory disease, chronic pelvic pain, infertility, ectopic pregnancy, and increased risk of other STIs acquisition. As the symptoms, when present, are usually similar in both infections, and in most of the cases these infections co-occur, the dual-test strategy, searching for both pathogens, should be preferred. In line with this, herein we focus on the main aspects of CT and NG infections, the clinical symptoms as well as the appropriate state-of-the-art diagnostic tests and treatment. Cost-effective strategies for controlling CT and NG infections worldwide are addressed. The treatment for both infections is based on antibiotics. However, the continuing global rise in the incidence of these infections, concomitantly with the increased risk of antibiotics resistance, leads to difficulties in their control, particularly in the case of NG infections. We also discuss the potential mechanism of tumorigenesis related to CT infections. The molecular bases of CT and NG infections are addressed, as they should provide clues for control or eradication, through the development of new drugs and/or effective vaccines against these pathogens.

Development of Cas13a-based Assays for Neisseria gonorrhoeae Detection and Gyrase A Determination

Background

Neisseria gonorrhoeae is one of the most common bacterial sexually transmitted infections. The emergence of antimicrobial-resistant N. gonorrhoeae is an urgent public health threat. Currently, diagnosis of N. gonorrhoeae infection requires expensive laboratory infrastructure, while antimicrobial susceptibility determination requires bacterial culture, both of which are infeasible in low-resource areas where prevalence is highest. Recent advances in molecular diagnostics, such as Specific High-sensitivity Enzymatic Reporter unLOCKing (SHERLOCK) using CRISPR-Cas13a and isothermal amplification, have the potential to provide low-cost detection of pathogen and antimicrobial resistance.

Methods and Results

We designed and optimized RNA guides and primer-sets for SHERLOCK assays capable of detecting N. gonorrhoeae via the por A gene and of predicting ciprofloxacin susceptibility via a single mutation in the gyrase A ( gyr A) gene. We evaluated their performance using both synthetic DNA and purified N. gonorrhoeae isolates. For por A, we created both a fluorescence-based assay and lateral flow assay using a biotinylated FAM reporter. Both methods demonstrated sensitive detection of 14 N. gonorrhoeae isolates and no cross-reactivity with 3 non-gonococcal Neisseria isolates. For gyr A, we created a fluorescence-based assay that correctly distinguished between 20 purified N. gonorrhoeae isolates with phenotypic ciprofloxacin resistance and 3 with phenotypic susceptibility. We confirmed the gyr A genotype predictions from the fluorescence-based assay with DNA sequencing, which showed 100% concordance for the isolates studied.

Conclusion

We report the development of Cas13a-based SHERLOCK assays that detect N. gonorrhoeae and differentiate ciprofloxacin-resistant isolates from ciprofloxacin-susceptible isolates.

Whole-Genome Sequencing to Predict Antimicrobial Susceptibility Profiles in Neisseria gonorrhoeae

BACKGROUND

Neisseria gonorrhoeae is a major public health problem due to increasing incidence and antimicrobial resistance. Genetic markers of reduced susceptibility have been identified; the extent to which those are representative of global antimicrobial resistance is unknown. We evaluated the performance of whole-genome sequencing (WGS) used to predict susceptibility to ciprofloxacin and other antimicrobials using a global collection of N. gonorrhoeae isolates.

METHODS

Susceptibility testing of common antimicrobials and the recently developed zolifodacin was performed using agar dilution to determine minimum inhibitory concentrations (MICs). We identified resistance alleles at loci known to contribute to antimicrobial resistance in N. gonorrhoeae from WGS data. We tested the ability of each locus to predict antimicrobial susceptibility.

RESULTS

A total of 481 N. gonorrhoeae isolates, collected between 2004 and 2019 and making up 457 unique genomes, were sourced from 5 countries. All isolates with demonstrated susceptibility to ciprofloxacin (MIC ≤0.06 μg/mL) had a wild-type gyrA codon 91. Multilocus approaches were needed to predict susceptibility to other antimicrobials. All isolates were susceptible to zoliflodacin, defined by an MIC ≤0.25 μg/mL.

CONCLUSIONS

Single marker prediction can be used to inform ciprofloxacin treatment of N. gonorrhoeae infection. A combination of molecular markers may be needed to determine susceptibility for other antimicrobials.

Loop-Mediated Isothermal Amplification Assay for Identifying Neisseria gonorrhoeae Nonmosaic penA-Targeting Strains Potentially Eradicable by Cefixime

Treatment regimens for gonorrhea have limited efficacy worldwide due to the rapid spread of antimicrobial resistance. Cefixime (CFM) is currently not recommended as a first-line treatment for gonorrhea due to the increasing number of resistant strains worldwide. Nonetheless, Neisseria gonorrhoeae strains can be eradicated by CFM at a 400 mg/day dose, provided that the strains are CFM responsive (MIC ≤ 0.064 mg/L). To develop a nonculture test for predicting the CFM responsiveness of N. gonorrhoeae strains, we developed an assay to detect N. gonorrhoeae nonmosaic penA using loop-mediated isothermal amplification (LAMP). To avoid false-positive reactions with commensal Neisseria spp. penA, we amplified specific regions of the N. gonorrhoeae penA (NG-penA-LAMP1) and also the nonmosaic N. gonorrhoeae penA (NG-penA-LAMP3). This assay was validated using isolated N. gonorrhoeae (n = 204) and Neisseria spp. (n = 95) strains. Clinical specimens (n = 95) with confirmed positivity in both culture and real-time PCR were evaluated to validate the system. The combination of the previously described NG-penA-LAMP1 and our new NG-penA-LAMP3 assays had high sensitivity (100%) and specificity (100%) for identifying N. gonorrhoeae carrying the nonmosaic type. To determine whether CFM could be applicable for gonorrhea treatment without culture testing, we developed a LAMP assay that targets penA allele-specific nonmosaic types for use as one of the tools for point-of-care testing of antimicrobial resistance. IMPORTANCE Neisseria gonorrhoeae is among the hot topics of "resistance guided therapy," one of the top 5 urgent antimicrobial threats according to the Centers for Disease Control and Prevention (CDC). There is a need either to develop new agents or to make effective use of existing agents, with the current limited number of therapeutic agents available. Knowing the drug susceptibility information of the target microorganism prior to treating patients is very useful in selecting an effective antibiotic, especially in gonococcal infections where drug resistance is prominent, and is also important in preventing treatment failure. In this study, we developed a new method for obtaining drug susceptibility profiles of Neisseria gonorrhoeae using the loop-mediated isothermal amplification (LAMP) method. The LAMP assay does not require expensive devices. Therefore, this method is expected to be a tool for point-of-care testing of antimicrobial resistance for individualized treatment in the future.

Bridging the gap between development of point-of-care nucleic acid testing and patient care for sexually transmitted infections

The incidence rates of sexually transmitted infections (STIs), including the four major curable STIs - chlamydia, gonorrhea, trichomoniasis and, syphilis - continue to increase globally, causing medical cost burden and morbidity especially in low and middle-income countries (LMIC). There have seen significant advances in diagnostic testing, but commercial antigen-based point-of-care tests (POCTs) are often insufficiently sensitive and specific, while near-point-of-care (POC) instruments that can perform sensitive and specific nucleic acid amplification tests (NAATs) are technically complex and expensive, especially for LMIC. Thus, there remains a critical need for NAAT-based STI POCTs that can improve diagnosis and curb the ongoing epidemic. Unfortunately, the development of such POCTs has been challenging due to the gap between researchers developing new technologies and healthcare providers using these technologies. This review aims to bridge this gap. We first present a short introduction of the four major STIs, followed by a discussion on the current landscape of commercial near-POC instruments for the detection of these STIs. We present relevant research toward addressing the gaps in developing NAAT-based STI POCT technologies and supplement this discussion with technologies for HIV and other infectious diseases, which may be adapted for STIs. Additionally, as case studies, we highlight the developmental trajectory of two different POCT technologies, including one approved by the United States Food and Drug Administration (FDA). Finally, we offer our perspectives on future development of NAAT-based STI POCT technologies.

Analysis of antimicrobial susceptibility testing methods and variables and in vitro activity of gepotidacin against urogenital Neisseria gonorrhoeae in men

Gepotidacin is a triazaacenaphthylene antibiotic with activity against Neisseria gonorrhoeae including strains resistant to current agents. We tested 145 N. gonorrhoeae isolates by agar dilution according to Gonococcal Isolate Surveillance Program and Clinical and Laboratory Standards Institute methodologies. Gepotidacin demonstrated a minimum inhibitory concentration (MIC)₅₀ of 0.25 μg/mL and a MIC₉₀ of 0.5 μg/mL (highest gepotidacin MIC was 1 μg/mL) against the 145 N. gonorrhoeae isolates tested. We also assessed the impact of test variables on antimicrobial susceptibility test results for gepotidacin, ciprofloxacin, and ceftriaxone against 10 N. gonorrhoeae isolates. Media type had the biggest effect but wasn't specific to gepotidacin. Gepotidacin MICs were also affected by inoculum, pH, and 10% CO₂. These in vitro data indicate that further study of gepotidacin is warranted for potential use in treating gonorrhea infections and highlight the importance of controlling for media type, inoculum, CO₂, and pH when performing MIC testing with gepotidacin.

Resistance-Guided Treatment of Gonorrhea: A Prospective Clinical Study

BACKGROUND

Novel treatment strategies to slow the continued emergence and spread of antimicrobial resistance in Neisseria gonorrhoeae are urgently needed. A molecular assay that predicts in vitro ciprofloxacin susceptibility is now available but has not been systematically studied in human infections.

METHODS

Using a genotypic polymerase chain reaction assay to determine the status of the N. gonorrhoeae gyrase subunit A serine 91 codon, we conducted a multisite prospective clinical study of the efficacy of a single oral dose of ciprofloxacin 500 mg in patients with culture-positive gonorrhea. Follow-up specimens for culture were collected to determine microbiological cure 5-10 days post-treatment.

RESULTS

Of the 106 subjects possessing culture-positive infections with wild-type gyrA serine N. gonorrhoeae genotype, the efficacy of single-dose oral ciprofloxacin treatment in the per-protocol population was 100% (95% 1-sided confidence interval, 97.5-100%).

CONCLUSIONS

Resistance-guided treatment of N. gonorrhoeae infections with single-dose oral ciprofloxacin was highly efficacious. The widespread introduction and scale-up of gyrA serine 91 genotyping in N. gonorrhoeae infections could have substantial medical and public health benefits in settings where the majority of gonococcal infections are ciprofloxacin susceptible.

CLINICAL TRIALS REGISTRATION

NCT02961751.

Developing a model to predict individualised treatment for gonorrhoea: a modelling study

OBJECTIVE

To develop a tool predicting individualised treatment for gonorrhoea, enabling treatment with previously recommended antibiotics, to reduce use of last-line treatment ceftriaxone.

DESIGN

A modelling study.

SETTING

England and Wales.

PARTICIPANTS

Individuals accessing sentinel health services.

INTERVENTION

Developing an Excel model which uses participants' demographic, behavioural and clinical characteristics to predict susceptibility to legacy antibiotics. Model parameters were calculated using data for 2015-2017 from the Gonococcal Resistance to Antimicrobials Surveillance Programme.

MAIN OUTCOME MEASURES

Estimated number of doses of ceftriaxone saved, and number of people delayed effective treatment, by model use in clinical practice. Model outputs are the predicted risk of resistance to ciprofloxacin, azithromycin, penicillin and cefixime, in groups of individuals with different combinations of characteristics (gender, sexual orientation, number of recent sexual partners, age, ethnicity), and a treatment recommendation.

RESULTS

Between 2015 and 2017, 8013 isolates were collected: 64% from men who have sex with men, 18% from heterosexual men and 18% from women. Across participant subgroups, stratified by all predictors, resistance prevalence was high for ciprofloxacin (range: 11%-51%) and penicillin (range: 6%-33%). Resistance prevalence for azithromycin and cefixime ranged from 0% to 13% and for ceftriaxone it was 0%. Simulating model use, 88% of individuals could be given cefixime and 10% azithromycin, saving 97% of ceftriaxone doses, with 1% of individuals delayed effective treatment.

CONCLUSIONS

Using demographic and behavioural characteristics, we could not reliably identify a participant subset in which ciprofloxacin or penicillin would be effective. Cefixime resistance was almost universally low; however, substituting ceftriaxone for near-uniform treatment with cefixime risks re-emergence of resistance to cefixime and ceftriaxone. Several subgroups had low azithromycin resistance, but widespread azithromycin monotherapy risks resistance at population level. However, this dataset had limitations; further exploration of individual characteristics to predict resistance to a wider range of legacy antibiotics may still be appropriate.

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

Neisseria gonorrhoeae, the causative agent of gonorrhoea, has rapidly evolved from an exquisitely susceptible pathogen into a 'superbug' with the capacity to exhibit an extensively drug resistant (XDR) phenotype. The threat of untreatable gonorrhoea now looms on the horizon while the arsenal of effective antimicrobial agents diminishes with time. Ceftriaxone remains the mainstay of first-line therapy as a single agent or as the backbone of a dual therapy regimen. The implementation of new assays to facilitate 'precision' treatment, based on the prediction of N. gonorrhoeae susceptibility to old anti-gonococcal drugs, may enable sparing use of ceftriaxone in those countries that can afford this technology. A few existing drugs, such as ertapenem, can be repositioned to help manage multi-drug resistant and XDR gonorrhoea. Recent clinical trials involving solithromycin and delafloxacin have generated disappointing results in that both agents failed to show non-inferiority to conventional ceftriaxone-based regimens. At present, zoliflodacin and gepotidacin appear to be the most promising antimicrobial agents in clinical development. Both drugs performed well in eradicating urogenital gonorrhoea in recent Phase 2 trials; however, treatment failures were reported at the oropharyngeal site, which is an important site of infection in men who have sex with men and sex workers. Given this observation, it is unlikely that either of these new agents could be promoted for monotherapy of gonorrhoea. The pre-clinical pipeline remains relatively empty of agents likely to progress to clinical development for gonorrhoea treatment and increased investment into gonorrhoea-specific drug discovery is recommended.

Evaluation of the ResistancePlus GC (beta) assay: a commercial diagnostic test for the direct detection of ciprofloxacin susceptibility or resistance in Neisseria gonorrhoeae

OBJECTIVES

To evaluate the performance of the ResistancePlus GC (beta) assay for the simultaneous detection of Neisseria gonorrhoeae and gyrA S91 markers of resistance (S91F) and susceptibility (WT) to ciprofloxacin, from both clinical specimens and isolates.

METHODS

Performance was assessed on several sample banks, including N. gonorrhoeae isolates (n = 822), non-gonococcal isolates (n = 110), N. gonorrhoeae-positive clinical specimens (n = 402) and N. gonorrhoeae-negative specimens (n = 290). Results were compared with previous testing data, including S91 genotyping and phenotypic resistance profiles.

RESULTS

Overall, the assay demonstrated 100% sensitivity for N. gonorrhoeae detection in clinical isolates. For gyrA S91 mutation detection in clinical isolates, the assay showed 100% sensitivity/specificity compared with the genotype, and >99%/>97% sensitivity/specificity when compared with phenotype. For positive clinical specimens, the assay demonstrated >96% sensitivity for N. gonorrhoeae detection and 100% sensitivity/specificity for gyrA S91 mutation detection. The assay demonstrated >99% specificity for N. gonorrhoeae detection against non-gonococcal isolates and 100% specificity for negative clinical specimens.

CONCLUSIONS

The ResistancePlus GC (beta) assay is suitable for the detection of N. gonorrhoeae and gyrA markers associated with resistance/susceptibility to ciprofloxacin directly in clinical samples. This assay could be implemented for the individualized treatment of gonorrhoea infections as well as to enhance current antimicrobial resistance surveillance methods.

Improved determination of Neisseria gonorrhoeae gyrase A genotype results in clinical specimens

BACKGROUND

The emergence of drug-resistant Neisseria gonorrhoeae has prompted the development of rapid molecular assays designed to determine antimicrobial susceptibility. One common assay uses high-resolution melt analysis to target codon 91 of the gyrase A gene (gyrA) to predict N. gonorrhoeae susceptibility to ciprofloxacin.

METHODS

We extracted DNA from remnant clinical specimens that had previously tested positive for N. gonorrhoeae using the Aptima Combo 2 for CT/NG assay (Hologic, San Diego, CA, USA). We selected DNA extracts from specimens with indeterminate, WT and mutant gyrA genotype results from a previous study using high-resolution melt analysis to detect the gyrA codon 91 mutation. We re-tested those specimens using the recently CE-marked ResistancePlus GC (beta) assay (SpeeDx, Sydney, Australia).

RESULTS

Of 86 specimens with indeterminate gyrA genotypes on high-resolution melt analysis, the ResistancePlus GC (beta) assay (SpeeDx) identified 30 (35%) WT, 22 (26%) mutant and 34 (40%) indeterminate gyrA genotypes.

CONCLUSIONS

The ResistancePlus GC (beta) assay showed improved N. gonorrhoeae gyrA genotype determination compared with a prior gyrA genotypic high-resolution melt assay.

Simultaneous Detection of Neisseria gonorrhoeae and Fluoroquinolone Resistance Mutations to Enable Rapid Prescription of Oral Antibiotics

BACKGROUND

Absence of rapid antimicrobial resistance testing of Neisseria gonorrhoeae (Ng) hinders personalized antibiotic treatment. To enable rapid ciprofloxacin prescription, a real-time polymerase chain reaction (PCR) for simultaneous detection of Ng and fluoroquinolone resistance-associated gyrA-S91F mutation was evaluated.

METHODS

Analytical NG quantitative PCR kit (NYtor BV) performance was assessed on 50 Ng transcription-mediated amplification (TMA)-negative and 100 Ng TMA-positive samples. To assess clinical use, 200 samples were prospectively analyzed, in parallel to routine diagnostic tests. Also, 50 urine, 50 anal, 50 pharyngeal, and 50 vaginal Ng TMA-positive samples were retrospectively analyzed. To assess if patients carried strains with different ciprofloxacin sensitivity at different anatomical locations, 50 urine/anal or vaginal/anal sample pairs collected during a single visit were analyzed.

RESULTS

The NG quantitative PCR kit showed 97% sensitivity and 100% specificity for Ng detection and 92% sensitivity and 99% specificity for gyrA-S91F detection. Relative to TMA results, 85% Ng detection sensitivity and 99% specificity were found. Regarding the 200 prospectively analyzed clinical samples, 13 were Ng positive, of which 10 were also tested for antibiotic susceptibility by culture. The kit showed concordance for GyrA-S91F detection in 9 of 10 samples. Ng was detected in 96% and 94% of vaginal and urine TMA-positive samples, in 84% of anal samples and only in 22% of pharyngeal samples. Discordant ciprofloxacin sensitivity was found for 2 of 26 characterized urine/anal sample pairs.

CONCLUSION

The NG quantitative polymerase chain reaction (qPCR) kit can be implemented in diagnostic testing for vaginal, urine, and anal Ng TMA-positive samples to enable rapid prescription of oral ciprofloxacin.

Expanding U.S. Laboratory Capacity for Neisseria gonorrhoeae Antimicrobial Susceptibility Testing and Whole-Genome Sequencing through the CDC's Antibiotic Resistance Laboratory Network

U.S. gonorrhea rates are rising, and antibiotic-resistant Neisseria gonorrhoeae (AR-Ng) is an urgent public health threat. Since implementation of nucleic acid amplification tests for N. gonorrhoeae identification, the capacity for culturing N. gonorrhoeae in the United States has declined, along with the ability to perform culture-based antimicrobial susceptibility testing (AST). Yet AST is critical for detecting and monitoring AR-Ng. In 2016, the CDC established the Antibiotic Resistance Laboratory Network (AR Lab Network) to shore up the national capacity for detecting several resistance threats including N. gonorrhoeae AR-Ng testing, a subactivity of the CDC's AR Lab Network, is performed in a tiered network of approximately 35 local laboratories, four regional laboratories (state public health laboratories in Maryland, Tennessee, Texas, and Washington), and the CDC's national reference laboratory. Local laboratories receive specimens from approximately 60 clinics associated with the Gonococcal Isolate Surveillance Project (GISP), enhanced GISP (eGISP), and the program Strengthening the U.S. Response to Resistant Gonorrhea (SURRG). They isolate and ship up to 20,000 isolates to regional laboratories for culture-based agar dilution AST with seven antibiotics and for whole-genome sequencing of up to 5,000 isolates. The CDC further examines concerning isolates and monitors genetic AR markers. During 2017 and 2018, the network tested 8,214 and 8,628 N. gonorrhoeae isolates, respectively, and the CDC received 531 and 646 concerning isolates and 605 and 3,159 sequences, respectively. In summary, the AR Lab Network supported the laboratory capacity for N. gonorrhoeae AST and associated genetic marker detection, expanding preexisting notification and analysis systems for resistance detection. Continued, robust AST and genomic capacity can help inform national public health monitoring and intervention.

Using the genetic characteristics of Neisseria gonorrhoeae strains with decreased susceptibility to cefixime to develop a molecular assay to predict cefixime susceptibility

BACKGROUND

In the last two decades, gonococcal strains with decreased cefixime susceptibility and cases of clinical treatment failure have been reported worldwide. Gonococcal strains with a cefixime minimum inhibitory concentration (MIC) ≥0.12 µg mL-1 are significantly more likely to fail cefixime treatment than strains with an MIC <0.12 µg mL-1. Various researchers have described the molecular characteristics of gonococcal strains with reduced cefixime susceptibility, and many have proposed critical molecular alterations that contribute to this decreased susceptibility.

METHODS

A systematic review of all published articles in PubMed through 1 November 2018 was conducted that report findings on the molecular characteristics and potential mechanisms of resistance for gonococcal strains with decreased cefixime susceptibility. The findings were summarised and suggestions were made for the development of a molecular-based cefixime susceptibility assay.

RESULTS

The penicillin-binding protein 2 (PBP2) encoded by the penA gene is the primary target of cefixime antimicrobial activity. Decreased cefixime susceptibility is conferred by altered penA genes with mosaic substitute sequences from other Neisseria (N.) species (identifiable by alterations at amino acid position 375-377) or by non-mosaic penA genes with at least one of the critical amino acid substitutions at positions 501, 542 and 551. Based on this review of 415 international cefixime decreased susceptible N. gonorrhoeae isolates, the estimated sensitivity for an assay detecting the aforementioned amino acid alterations would be 99.5% (413/415).

CONCLUSIONS

Targeting mosaic penA and critical amino acid substitutions in non-mosaic penA are necessary and may be sufficient to produce a robust, universal molecular assay to predict cefixime susceptibility.

Genotypic and Phenotypic Characterization of Antimicrobial Resistance in Neisseria gonorrhoeae: a Cross-Sectional Study of Isolates Recovered from Routine Urine Cultures in a High-Incidence Setting

The objectives of this study were to perform genomic and phenotypic characterization of antimicrobial resistance in Neisseria gonorrhoeae isolates recovered from urine samples from patients in St. Louis, MO, USA. Sixty-four clinical isolates were banked over a 2-year period and subjected to antimicrobial susceptibility testing (AST) by Kirby-Bauer disk diffusion (penicillin, tetracycline, cefuroxime, and ciprofloxacin) and gradient diffusion (tetracycline, doxycycline, azithromycin, ceftriaxone, cefixime, ciprofloxacin, gemifloxacin, and delafloxacin). The medical records for the patients were evaluated to determine the demographics, location, and prescribed treatment regimen. Isolate draft genomes were assembled from Illumina shotgun sequencing data, and resistance determinants were identified by ResFinder and PointFinder. Of the 64 isolates, 97% were nonsusceptible to penicillin, with resistant isolates all containing the blaTEM-1b gene; 78 and 81% of isolates were nonsusceptible to tetracycline and doxycycline, respectively, with resistant isolates all containing the tet(M) gene. One isolate was classified as non-wild-type to azithromycin, and all isolates were susceptible to ceftriaxone; 89% of patients received this combination of drugs as first-line therapy. Six percent of isolates were resistant to ciprofloxacin, with most resistant isolates containing multiple gyrA and parC mutations. Correlation between disk and gradient diffusion AST devices was high for tetracycline and ciprofloxacin (R2 > 99% for both). The rates of N. gonorrhoeae antibiotic resistance in St. Louis are comparable to current rates reported nationally, except ciprofloxacin resistance was less common in our cohort. Strong associations between specific genetic markers and phenotypic susceptibility testing hold promise for the utility of genotype-based diagnostic assays to guide directed antibiotic therapy.IMPORTANCENeisseria gonorrhoeae causes the sexually transmitted infection gonorrhea, which is most commonly diagnosed using a DNA-based detection method that does not require growth and isolation of N. gonorrhoeae in the laboratory. This is problematic because the rates of antibiotic resistance in N. gonorrhoeae are increasing, but without isolating the organism in the clinical laboratory, antibiotic susceptibility testing cannot be performed on strains recovered from clinical specimens. We observed an increase in the frequency of urine cultures growing N. gonorrhoeae after we implemented a total laboratory automation system for culture in our clinical laboratory. Here, we report on the rates of resistance to multiple historically used, first-line, and potential future-use antibiotics for 64 N. gonorrhoeae isolates. We found that the rates of antibiotic resistance in our isolates were comparable to national rates. Additionally, resistance to specific antibiotics correlated closely with the presence of genetic resistance genes, suggesting that DNA-based tests could also be designed to guide antibiotic therapy for treating gonorrhea.

Antimicrobial Resistance in Neisseria gonorrhoeae: Proceedings of the STAR Sexually Transmitted Infection-Clinical Trial Group Programmatic Meeting

The goal of the Sexually Transmitted Infection Clinical Trial Group's Antimicrobial Resistance (AMR) in Neisseria gonorrhoeae (NG) meeting was to assemble experts from academia, government, nonprofit and industry to discuss the current state of research, gaps and challenges in research and technology and priorities and new directions to address the continued emergence of multidrug-resistant NG infections. Topics discussed at the meeting, which will be the focus of this article, include AMR NG global surveillance initiatives, the use of whole genome sequencing and bioinformatics to understand mutations associated with AMR, mechanisms of AMR, and novel antibiotics, vaccines and other methods to treat AMR NG. Key points highlighted during the meeting include: (i) US and International surveillance programs to understand AMR in NG; (ii) the US National Strategy for combating antimicrobial-resistant bacteria; (iii) surveillance needs, challenges, and novel technologies; (iv) plasmid-mediated and chromosomally mediated mechanisms of AMR in NG; (v) novel therapeutic (eg, sialic acid analogs, factor H [FH]/Fc fusion molecule, monoclonal antibodies, topoisomerase inhibitors, fluoroketolides, LpxC inhibitors) and preventative (eg, peptide mimic) strategies to combat infection. The way forward will require renewed political will, new funding initiatives, and collaborations across academic and commercial research and public health programs.

A Cost Analysis of Gyrase A Testing and Targeted Ciprofloxacin Therapy Versus Recommended 2-Drug Therapy for Neisseria gonorrhoeae Infection

BACKGROUND

Novel approaches to combating drug-resistant Neisseria gonorrhoeae infections are urgently needed. Targeted therapy with ciprofloxacin has been made possible by a rapid assay for genotyping the gyrase A (gyrA) gene; a nonmutated gene reliably predicts susceptibility to ciprofloxacin.

METHODS

We determined the costs of running the gyrA assay, 500 mg of ciprofloxacin, 250 mg of ceftriaxone injection, and 1000 mg of azithromycin. Cost estimates for gyrA testing included assay reagents and labor. Cost estimates for ceftriaxone included medication, injection, administration, supplies, and equipment. We measured the cost of using the gyrA assay and treatment based on genotype using previously collected data over a 13-month period between November 2015 and November 2016 for all N. gonorrhoeae cases diagnosed at UCLA. We subsequently developed 3 cost models, varying the frequency of testing and prevalence of N. gonorrhoeae infections with ciprofloxacin-resistant or genotype-indeterminate results. We compared those estimates with the cost of recommended 2-drug therapy (ceftriaxone and azithromycin).

RESULTS

Based on a 65.3% prevalence of cases with ciprofloxacin-resistant or genotype indeterminate N. gonorrhoeae infections when running an average of 1.7 tests per day, the per-case cost of gyrA genotyping and targeted therapy was US $197.19. The per-case cost was US $155.16 assuming a 52.6% prevalence of ciprofloxacin-resistant or genotype-indeterminate infections when running an average of 17 tests per day. The per-case cost of 2-drug therapy was US $142.75.

CONCLUSIONS

Direct costs of gyrA genotyping and targeted ciprofloxacin therapy depend on the prevalence of ciprofloxacin-resistant or genotype-indeterminate infections and testing frequency.

A multisite implementation of a real-time polymerase chain reaction assay to predict ciprofloxacin susceptibility in Neisseria gonorrhoeae

There are no commercially available Food and Drug Administration-cleared rapid tests for Neisseria gonorrhoeae antimicrobial susceptibility testing. This study evaluated the performance of a laboratory-developed real-time polymerase chain reaction assay for genotyping the gyrA gene to determine antimicrobial susceptibility to ciprofloxacin. Validation and clinical performance of the gyrA assay were evaluated across 3 geographic locations (Los Angeles, San Francisco, Philadelphia). Following validation, clinical specimens were collected in Aptima Combo2® CT/NG transport medium from asymptomatic persons who tested positive for Neisseria gonorrhoeae and evaluated for assay percent reportable (i.e., proportion of N. gonorrhoeae-positive specimens that yielded a gyrA genotype). The percentage of gyrA genotyping results differed by laboratory and specimen type. The proportion of specimens that were reportable was best for urine/genital specimens (genotyped = 76.4% (95% confidence interval, 69.9-82%)) followed by rectal (genotyped = 67.2% (95% confidence interval, 63.4-70.6%)) and then pharyngeal specimens (genotyped = 36.1%, (95% confidence interval, 31.9-40.5%)). Overall, asymptomatic patients with N. gonorrhoeae yielded an interpretable genotype 57.2% (784/1370) of the time, of which 480 were wild-type gyrA, resulting in 61% (480/784) being potentially treatable with ciprofloxacin.

Gonococcal antimicrobial resistance: 80 years in the making

Antimicrobial resistance has been a problem for the treatment of gonorrhoea since the introduction of sulfa drugs in the 1930s. The gonococcus has a remarkable ability to obtain the genetic elements required to develop resistance and for these resistant strains to then widely disseminate. Many decades of antibiotic monotherapy have seen the introduction of a number of antibiotic classes herald a promising new era of treatment only to subsequently fail due to resistance development. The world is now faced with the prospect of extensively resistant Neisseria gonorrhoea and requires a coordinated action plan to detect and treat these resistant strains.

Molecular screening for Neisseria gonorrhoeae antimicrobial resistance markers in Nigerian men who have sex with men and transgender women

Antimicrobial-resistant Neisseria gonorrhoeae (NG) is a global public health issue that threatens effectiveness of current treatments of NG. Increased use of nucleic acid amplification tests (NAATs) in lieu of cultures makes obtaining clinical isolates for susceptibility testing difficult and samples collected in commercial transport buffer for NAATs do not preserve viable organism, while molecular methods of assessing antibiotic susceptibility do not require viable organism. We evaluated 243 NG-positive samples in Aptima transport media including urine, oral, and rectal swabs from Nigerian men who have sex with men for markers to penicillinase-producing NG, ciprofloxacin ( GyrA and ParC mutations), and extended spectrum cephalosporins (ESCs, PenA mosaic [allele X], PonA, mtrR, PorB mutations) by real-time PCR. NG DNA was recovered in 75% (183/243) of samples. Of these, 93% (171/183) were positive for at least one resistance marker. We observed a prevalence of dual resistance markers to penicillin and ciprofloxacin at 46.2% (79/171). Six percent of samples (10/171) tested positive for the PenA mosaic (allele X) ESC marker. These data indicate that antibiotic-resistant NG is common in Nigeria. Laboratory and clinical capacity building in Nigeria should include development of methods to culture NG and determine antimicrobial susceptibility.

Advancing point of care diagnostics for the control and prevention of STIs: the way forward

WHO recognises the global impact of sexually transmitted infections (STIs) on global public health and individual sexual and reproductive health and well-being. As a component of the WHO Global Health Sector Strategy for the control and prevention of STIs, there has been a growing recognition of the importance of integrating point-of-care tests (POCTs) into overall strategic planning. The process of integrating STI POCTs, in addition to providing a definitive diagnosis and appropriate treatment in a single visit, also includes innovative delivery options, such as on-site delivery, community-based testing (including screening), as well as self-testing at home after purchase of a test online or over-the-counter. WHO organised two technical consultations in May 2014 and July 2015. This article summarises the discussions of the meeting participants on advancing the use of POCTs to control and prevent STIs. The following priorities were identified: the need for pathogens' target discovery; encouragement of multiplexing, miniaturisation, simplification and connectivity; promotion of standardisation of evaluation of new diagnostic platforms across all stages of the evaluation pipeline; the need for an investment case, modelling and scenarios to ensure buy-in among key stakeholders, including developers and the private sector; the need for norms and standards, including guidelines, to support introduction of STI POCTs in programmes; anticipating potential tensions between different parties at the implementation level; and leveraging on the global initiative, Sustainable Development Goals (SDGs)/global health sector STI strategy, to sustain investment in STI POCT programmes. There is a rich pipeline of diagnostic products, but some have stalled in development. An approach to accelerate the evaluation of new diagnostics is to set up a competent network of evaluation sites ahead of time, harmonise regulatory approval processes with development of models to estimate cost-effectiveness, informed by better STI data. This should result in accelerating policy development. Although it may be some time before good POCTs can be widely implemented in low resource settings, it is important to be a catalyst for continued development and use of these essential tools as an integral part of both the WHO Global Health Sector Strategy and the agenda for 2030.

Antimicrobial resistance of Neisseria gonorrhoeae in Germany: low levels of cephalosporin resistance, but high azithromycin resistance

Background

The widespread antimicrobial resistance of Neisseria gonorrhoeae is a serious problem for the treatment and control of gonorrhoea. Many of the previously effective therapeutic agents are no longer viable. Because N. gonorrhoeae infections are not reportable in Germany, only limited data on disease epidemiology and antimicrobial susceptibility patterns are available. The Gonococcal Resistance Network (GORENET) is a surveillance project to monitor trends in the antimicrobial susceptibility of N. gonorrhoeae in Germany in order to guide treatment algorithms and target future prevention strategies.

Methods

Between April 2014 and December 2015, data on patient-related information were collected from laboratories nationwide, and susceptibility testing was performed on 537 N. gonorrhoeae isolates forwarded from the network laboratories to the Conciliar Laboratory for gonococci. Susceptibility results for cefixime, ceftriaxone, azithromycin, ciprofloxacin and penicillin were defined according to EUCAST 4.0 standards. Percentages, medians and interquartile ranges (IQR) were calculated.

Results

Altogether, 90% of isolates were from men. The median age was 32 (IQR 25–44) years for men and 25 (IQR 22–40) years for women (p-value < 0.001). The most frequently tested materials among men were urethral (96.1%) and rectal swabs (1.7%), and among women, it was mainly endocervical and vaginal swabs (84.3%). None of the isolates were resistant to ceftriaxone. Furthermore, 1.9% (in 2014) and 1.4% (in 2015) of the isolates were resistant to cefixime, 11.9% and 9.8% showed resistance against azithromycin, 72.0% and 58.3% were resistant to ciprofloxacin, and 29.1% and 18.8% were resistant to penicillin.

Conclusions

Resistance to ceftriaxone was not detected, and the percentage of isolates with resistance to cefixime was low, whereas azithromycin resistance showed high levels during the observation period. The rates of ciprofloxacin resistance and penicillin resistance were very high across Germany. Continued surveillance of antimicrobial drug susceptibilities for N. gonorrhoeae remains highly important to ensure efficient disease management.

Implementation of a Rapid Genotypic Assay to Promote Targeted Ciprofloxacin Therapy of Neisseria gonorrhoeae in a Large Health System

Multidrug-resistant Neisseria gonorrhoeae is a top threat to public health. In November 2015, UCLA Health introduced a rapid gyrase A (gyrA) genotypic assay for prediction of Neisseria gonorrhoeae susceptibility to ciprofloxacin. We found a significant reduction in ceftriaxone use with a concomitant increase in targeted therapy.

Wild-Type Gyrase A Genotype of Neisseria gonorrhoeae Predicts In Vitro Susceptibility to Ciprofloxacin: A Systematic Review of the Literature and Meta-Analysis

Multidrug-resistant Neisseria gonorrhoeae infections have been declared 1 of the top 3 urgent threats to public health. Approaches to combat resistance include targeted therapy with antibiotics previously thought to be ineffective, made possible by rapid molecular assays to predict susceptibility. Previous studies have associated the gyrase A (gyrA) gene of N. gonorrhoeae with in vitro resistance to ciprofloxacin. We conducted a systematic review of studies comparing N. gonorrhoeae gyrA genotype results with conventional antimicrobial susceptibility testing results. We identified 31 studies meeting inclusion criteria, among which 7 different loci for mutations in the gyrA gene were identified, from 16 countries between the years of 1996 and 2016. We then performed a meta-analysis among those studies stratifying by use of real-time polymerase chain reaction (PCR) or non-real-time PCR technique, and compared the summary receiver operating characteristic curves between the 2 PCR methods. Among studies using real-time PCR, the pooled estimate of sensitivity and specificity of gyrA genotype results for the prediction of N. gonorrhoeae susceptibility to ciprofloxacin were 98.2% (95% confidence interval [CI], 96.5-99.1%) and 98.6% (95% CI, 97.0-99.3%), respectively. The summary operating characteristic curves for studies using real-time PCR techniques were well separated from those using non-real-time PCR techniques, with only slight overlap in the CIs, suggesting that real-time PCR techniques were a more accurate approach. GyrA genotype testing is a novel approach to combating the emergence of multidrug-resistant N. gonorrhoeae and is a sensitive and specific method to predict in vitro ciprofloxacin susceptibility.

[Laboratory practices: diagnostics and antibiotics resistance testing of Neisseria gonorrhoeae in Germany]

Recent years have seen a world-wide increase in antimicrobial resistance (AMR) in cases of infection with Neisseria gonorrhoeae (NG). NG infection is not notifiable in Germany and there is a lack of information available about the spread and AMR of NG infections. The objective of the study was to provide information on diagnostic methods and AMR testing in cases of NG infections in German laboratories. A cross-sectional survey was undertaken in Germany between June and August 2013 using an online questionnaire. Laboratories performing NG diagnostics were identified and described with regard to the diagnostic methods used, the number of tests performed, the antibiotics tested and the AMR observed, in addition to general laboratory information. In total, 188 of the 521 participating laboratories performed NG diagnostics; these were included in the further statistical analysis. 92.6 % of the 188 laboratories performed culture. A median of 60 (IQR 15-270) samples per quarter (SPQ) were tested, with an overall positivity rate of 4.1 and 6.9 % among men. Most (82.1 %) of the 151 laboratories performing NG culture tested for AMR as well. The most frequently tested antibiotics were ciprofloxacin (94.8 %), penicillin (93.1 %), doxycycline (70.0 %) and ceftriaxone (67.2 %). The most frequently observed AMR ever were those against ciprofloxacin (87.1 %), penicillin (78.3 %), doxycycline (56.6 %) and azithromycin (35.1 %; all percentages refer to laboratories). The laboratories used different standards regarding susceptibility criteria. The emergence and spread of AMR shows that it is crucial to assess and monitor the scope and trends of multidrug-resistant gonorrhea. The data collected on diagnostic methods and AMR testing in cases of NG infections in German laboratories constitute an important basis for future monitoring.

Molecular tests for the detection of antimicrobial resistant Neisseria gonorrhoeae: when, where, and how to use?

PURPOSE OF REVIEW

Molecular methods for the diagnosis of Neisseria gonorrhoeae are replacing bacterial culture in many settings. This review focuses on recent progress in the development of molecular tests to detect resistant N. gonorrhoeae both to enhance surveillance and to guide decisions about individual patient management.

RECENT FINDINGS

Assays to enhance surveillance have been developed to detect determinants of resistance for all antibiotics used as first-line gonorrhoea treatment, or to detect specific 'superbug' strains, but few have been applied in clinical practice. The most advanced strategy relevant to individual case management is to identify ciprofloxacin-sensitive strains so that unnecessary use of ceftriaxone can be avoided. Cross-reactivity with pharyngeal commensal Neisseria species reduces specificity and is a challenge for many assays.

SUMMARY

Progress with laboratory-based molecular tests to detect gonococcal resistance is being made but substantial challenges remain. No laboratory-based assay has been subjected to a field evaluation and no assay so far can be used as a point-of-care test. Given the threat of antimicrobial resistance, now is the time to exploit the molecular technologies used for diagnosis and to invest in the development of molecular gonococcal resistance tests that can be implemented for public health good.

Real-time PCR detection of Neisseria gonorrhoeae susceptibility to penicillin

OBJECTIVES

The objective of this study was to develop a real-time PCR assay targeting the gonococcal porB gene (PorB-PCR) for predicting susceptibility of Neisseria gonorrhoeae to penicillin. This complements a previously described PCR assay for detecting penicillinase-producing N. gonorrhoeae (PPNG) developed by our laboratory (PPNG-PCR).

METHODS

The PorB-PCR assay was designed using six probes to characterize various combinations of amino acids at positions 101 and 102 of the PorB1b class protein, including the WT G101/A102 and mutant G101K/A102D, G101K/A102N and G101K/A102G sequences, as well as the PorB1a sequence. The ability of these sequences to predict penicillin susceptibility was initially assessed using 2307 N. gonorrhoeae isolates from throughout Australia for which phenotypic susceptibility data were available. The assay was then applied to N. gonorrhoeae-positive clinical specimens (n = 70). Specificity was assessed by testing commensal Neisseria strains (n = 75) and N. gonorrhoeae-negative clinical specimens (n = 171).

RESULTS

Testing of the 2307 N. gonorrhoeae isolates using PorB-PCR to detect G101/A102 and PorB1a sequences identified a total of 78.4% (61.2% and 17.2%, respectively) of penicillin-susceptible isolates with specificities of 97.4% and 99.3% and positive predictive values of 98.8% and 98.9%, where PPNG strains were simultaneously identified and excluded. Similar performance data were obtained when the PorB-PCR assay was applied to the N. gonorrhoeae-positive clinical specimens. No false-positive results were observed for the N. gonorrhoeae-negative samples and no cross-reactions were observed with the non-gonococcal species.

CONCLUSIONS

When used in parallel with the previously described PPNG-PCR, the PorB-PCR approach has the potential to facilitate individualized treatment of gonorrhoea using penicillin.

Disseminated gonococcal infection: an unusual presentation

Gonococcus typically affects the mucosal surfaces but in rare cases can spread to bloodstream causing disseminated gonococcal infection (DGI). The usual presentation of DGI is rash, polyarthralgia, and tenosynovitis. We present the case of a 23-year-old female who presented to our hospital with pustular rash and tenosynovitis of hand and was sent home on Augmentin. Her symptoms worsened despite treatment and she presented back to the ED. On investigation, she was found to have DGI and was appropriately treated. DGI should be kept in mind in sexually active youngsters who have only one or two features of the classic triad of rash, tenosynovitis, and arthritis. Timely management and appropriate treatment of DGI is very important to avoid complications and morbidity.

Multicenter Investigation of Gepotidacin (GSK2140944) Agar Dilution Quality Control Determinations for Neisseria gonorrhoeae ATCC 49226

Gepotidacin, a novel triazaacenaphthylene antibacterial agent, is the first in a new class of type IIA topoisomerase inhibitors with activity against many biothreat and conventional pathogens, including Neisseria gonorrhoeae To assist ongoing clinical studies of gepotidacin to treat gonorrhea, a multilaboratory quality assurance investigation determined the reference organism (N. gonorrhoeae ATCC 49226) quality control MIC range to be 0.25 to 1 μg/ml (88.8% of gepotidacin MIC results at the 0.5 μg/ml mode).

A real-time PCR assay for direct characterization of the Neisseria gonorrhoeae GyrA 91 locus associated with ciprofloxacin susceptibility

OBJECTIVES

The objective of this study was to develop a real-time PCR method for specific detection of the gonococcal GyrA amino acid 91 locus directly in clinical samples so as to predict Neisseria gonorrhoeae ciprofloxacin susceptibility.

METHODS

The real-time PCR assay, GyrA91-PCR, was designed using two probes, one for detection of the WT S91 sequence and the other for detection of the S91F alteration. The performance of the assay was initially assessed using characterized N. gonorrhoeae isolates (n = 70), a panel of commensal Neisseria and Moraxella species (n = 55 isolates) and clinical samples providing negative results by a commercial N. gonorrhoeae nucleic acid amplification test (NAAT) method (n = 171). The GyrA91-PCR was then applied directly to N. gonorrhoeae NAAT-positive clinical samples (n = 210) from the year 2014 for which corresponding N. gonorrhoeae isolates with susceptibility results were also available.

RESULTS

The GyrA91-PCR accurately characterized the GyrA 91 locus of all 70 N. gonorrhoeae isolates (sensitivity = 100%, 95% CI = 94.9%-100%), whereas all non-gonococcal isolates and N. gonorrhoeae NAAT-negative clinical samples gave negative results by the GyrA91-PCR (specificity = 100%, 95% CI = 98.4%-100%). When applied to the 210 N. gonorrhoeae NAAT-positive clinical samples, the GyrA91-PCR successfully characterized 195 samples (92.9%, 95% CI = 88.5%-95.9%). When compared with the corresponding bacterial culture results, positivity by the GyrA91-PCR WT probe correctly predicted N. gonorrhoeae susceptibility to ciprofloxacin in 161 of 162 (99.4%, 95% CI = 96.6%-99.9%) samples.

CONCLUSIONS

The use of a PCR assay for detection of mutation in gyrA applied directly to clinical samples can predict ciprofloxacin susceptibility in N. gonorrhoeae.

Current and future antimicrobial treatment of gonorrhoea - the rapidly evolving Neisseria gonorrhoeae continues to challenge

Neisseria gonorrhoeae has developed antimicrobial resistance (AMR) to all drugs previously and currently recommended for empirical monotherapy of gonorrhoea. In vitro resistance, including high-level, to the last option ceftriaxone and sporadic failures to treat pharyngeal gonorrhoea with ceftriaxone have emerged. In response, empirical dual antimicrobial therapy (ceftriaxone 250–1000 mg plus azithromycin 1–2 g) has been introduced in several particularly high-income regions or countries. These treatment regimens appear currently effective and should be considered in all settings where local quality assured AMR data do not support other therapeutic options. However, the dual antimicrobial regimens, implemented in limited geographic regions, will not entirely prevent resistance emergence and, unfortunately, most likely it is only a matter of when, and not if, treatment failures with also these dual antimicrobial regimens will emerge. Accordingly, novel affordable antimicrobials for monotherapy or at least inclusion in new dual treatment regimens, which might need to be considered for all newly developed antimicrobials, are essential. Several of the recently developed antimicrobials deserve increased attention for potential future treatment of gonorrhoea. In vitro activity studies examining collections of geographically, temporally and genetically diverse gonococcal isolates, including multidrug-resistant strains particularly with resistance to ceftriaxone and azithromycin, are important. Furthermore, understanding of effects and biological fitness of current and emerging (in vitro induced/selected and in vivo emerged) genetic resistance mechanisms for these antimicrobials, prediction of resistance emergence, time-kill curve analysis to evaluate antibacterial activity, appropriate mice experiments, and correlates between genetic and phenotypic laboratory parameters, and clinical treatment outcomes, would also be valuable. Subsequently, appropriately designed, randomized controlled clinical trials evaluating efficacy, ideal dose, toxicity, adverse effects, cost, and pharmacokinetic/pharmacodynamics data for anogenital and, importantly, also pharyngeal gonorrhoea, i.e. because treatment failures initially emerge at this anatomical site. Finally, in the future treatment at first health care visit will ideally be individually-tailored, i.e. by novel rapid phenotypic AMR tests and/or genetic point of care AMR tests, including detection of gonococci, which will improve the management and public health control of gonorrhoea and AMR. Nevertheless, now is certainly the right time to readdress the challenges of developing a gonococcal vaccine.

Will targeting oropharyngeal gonorrhoea delay the further emergence of drug-resistant Neisseria gonorrhoeae strains?

Gonorrhoea is an important sexually transmitted infection associated with serious complications and enhanced HIV transmission. Oropharyngeal infections are often asymptomatic and will only be detected by screening. Gonococcal culture has low sensitivity (<50%) for detecting oropharyngeal gonorrhoea, and, although not yet approved commercially, nucleic acid amplification tests (NAAT) are the assay of choice. Screening for oropharyngeal gonorrhoea should be performed in high-risk populations, such as men-who-have-sex-with-men(MSM). NAATs have a poor positive predictive value when used in low-prevalence populations. Gonococci have repeatedly thwarted gonorrhoea control efforts since the first antimicrobial agents were introduced. The oropharyngeal niche provides an enabling environment for horizontal transfer of genetic material from commensal Neisseria and other bacterial species to Neisseria gonorrhoeae. This has been the mechanism responsible for the generation of mosaic penA genes, which are responsible for most of the observed cases of resistance to extended-spectrum cephalosporins (ESC). As antimicrobial-resistant gonorrhoea is now an urgent public health threat, requiring improved antibiotic stewardship, laboratory-guided recycling of older antibiotics may help reduce ESC use. Future trials of antimicrobial agents for gonorrhoea should be powered to test their efficacy at the oropharynx as this is the anatomical site where treatment failure is most likely to occur. It remains to be determined whether a combination of frequent screening of high-risk individuals and/or laboratory-directed fluoroquinolone therapy of oropharyngeal gonorrhoea will delay the further emergence of drug-resistant N. gonorrhoeae strains.