Gentamicin, azithromycin and ceftriaxone in the treatment of gonorrhoea: the relationship between antibiotic MIC and clinical outcome

Neisseria gonorrhoeae treatment failure to the recommended antibiotic regimen-Québec, Canada, 2015-19

OBJECTIVE

To describe Neisseria gonorrhoeae treatment failure to the recommended antimicrobial regimens (azithromycin, cefixime and ceftriaxone).

METHODS

Our study was a longitudinal analysis of treatment failures from an observational open cohort of gonococcal infection cases collected in Québec, Canada (n = 2547) between September 2015 and December 2019. Epidemiological and clinical data were collected using a self-administered questionnaire, direct case interviews and chart reviews. Antimicrobial susceptibility testing was performed using the agar dilution method. To be retained as a treatment failure, cases must have had (i) a laboratory-confirmed gonococcal infection; (ii) a documented treatment; (iii) a positive test of cure (TOC) performed within a defined period and (iv) no sexual contact (vaginal, oral or anal), even protected with a condom, between the beginning of treatment and the positive TOC. A broader definition, including suspected cases, was also examined.

RESULTS

Among 1593 cases where a TOC was performed, 83 had a positive TOC: 11 were retained as treatment failure, and 6 were considered suspected cases (overall = 17/1593; 1.1%). Possible explanations for retained or suspected treatment failure included resistance to the antibiotics used for treatment (n = 1), pharyngeal infection (n = 9, of which 5 had been treated with ceftriaxone and 4 with other regimens); and azithromycin monotherapy (n = 1). Some cases had more than one potential explanation.

CONCLUSIONS

Treatment failure occurred in 1.1% of cases of Neisseria gonorrhoeae infection for which a TOC was performed, including some cases of pharyngeal infection treated with ceftriaxone.

Increasing azithromycin resistance in Neisseria gonorrhoeae due to NG-MAST 12302 clonal spread in Canada, 2015-2018

Objectives: Azithromycin resistant (AZIR) gonorrhea has been steadily increasing in Canada over the past decade which is cause for alarm as azithromycin (AZI) has been part of the combination therapy recommended by the Canadian Guidelines on Sexually Transmitted Infections (CGSTI) since 2012.

Method: Neisseria gonorrhoeae (NG) with AZI MICs ≥ 1 mg/L collected between 2015 and 2018 as part of the Gonococcal Antimicrobial Surveillance Program-Canada underwent antimicrobial susceptibility testing, molecular typing and whole genome sequencing. Regional, demographic and clinical isolation site comparisons were made to aid in our understanding of AZI susceptibility trending.

Results: 3,447 NG with AZI MICs ≥ 1 mg/L were identified in Canada, increasing from 6.3% in 2015 to 26.5% of isolates in 2018. Central Canada had the highest proportion rising from 9.2% in 2015 to 31.2% in 2018. 273 different NG-MAST sequence types were identified among these isolates with ST-12302 the most prevalent (50.9%). Whole genome sequencing identified the Neisseria lactamica -like mosaic mtr locus as the mechanism of AZIR in isolates of ST-12302 and isolates genetically similar (differ by ≤ 5 base pairs) designated as the ST-12302 genogroup, accounting for 65.2% of study isolateswhich were originally identified in central Canada but spread to other regions by 2018.

Conclusion: Genomic analysis indicated that AZIR in Canadian NG expanded rapidly due to clonal spread of the ST-12302 genogroup. The rapid expansion of this AZIR clonal group in all regions of Canada is of concern. CGSTI are currently under review to address the increase in AZIR in Canada.

The Expanded Role of Chitosan in Localized Antimicrobial Therapy

Chitosan is one of the most studied natural origin polymers for biomedical applications. This review focuses on the potential of chitosan in localized antimicrobial therapy to address the challenges of current rising antimicrobial resistance. Due to its mucoadhesiveness, chitosan offers the opportunity to prolong the formulation residence time at mucosal sites; its wound healing properties open possibilities to utilize chitosan as wound dressings with multitargeted activities and more. We provide an unbiased overview of the state-of-the-art chitosan-based delivery systems categorized by the administration site, addressing the site-related challenges and evaluating the representative formulations. Specifically, we offer an in-depth analysis of the current challenges of the chitosan-based novel delivery systems for skin and vaginal infections, including its formulations optimizations and limitations. A brief overview of chitosan's potential in treating ocular, buccal and dental, and nasal infections is included. We close the review with remarks on toxicity issues and remaining challenges and perspectives.

The Accuracy of Molecular Detection Targeting the Mutation C2611T for Detecting Moderate-Level Azithromycin Resistance in Neisseria gonorrhoeae: A Systematic Review and Meta-Analysis

BACKGROUND

Neisseria gonorrhoeae (N. gonorrhoeae) is now recognized as a commonly reported sexually transmitted pathogen, and the increasing drug resistance of N. gonorrhoeae has become a serious public health problem. The accuracy of molecular detection for detecting moderate-level azithromycin resistance is not well-established. We summarized the data from studies of the N. gonorrhoeae 23S rRNA mutation at position 2611 with azithromycin resistance to determine the relationship between the mutation and resistance.

METHODS AND FINDINGS

In this systematic review and meta-analysis, two researchers independently searched six databases for studies with data for the azithromycin minimum inhibitory concentrations (MICs) and the 23S rRNA mutation C2611T of each N. gonorrhoeae isolate. Since the breakpoint of moderate-level resistance to azithromycin (ML-AzmR) was not determined, we divided the moderate level into two groups according to the range of MICs (moderate resistance limited to 2-128 mg/L or 4-128 mg/L) for data extraction. A random-effects model was used to calculate the pooled sensitivity rate, the specificity rate, the pooled positive likelihood ratio (PLR), the negative likelihood ratio (NLR), and the diagnostic odds ratio (DOR). Meta-regression analyses by detection method, isolates sampling (a random sample or not), location, and sample size were performed to explore the possible causes of heterogeneity. The potential publication bias of the included studies was conducted by the Deeks' test. We included 20 studies in our study: 20 studies have data of N. gonorrhoeae with MICs between 2 and 128 mg/L with mutation or without mutation at position 2611(4759 samples), and 14 studies have data of N. gonorrhoeae with MICs between 4 and 128 mg/L (3367 samples). In the group with the moderate level of 2-128 mg/L, the pooled sensitivity rate of the molecular assays was determined to be 71.9% (95% CI, 67.6-74%), the pooled specificity rate was 98.7% (95% CI, 98.2-99.0%), and the DOR ranged from 55.0 to 351.3 (mean, 139.1). In the 4-128 mg/L group, the pooled sensitivity rate was 91.9% (95% CI, 88.9-94.2%), the pooled specificity rate was 95.9% (95% CI, 95.1-96.6%), and the DOR ranged from 41.9 to 364.1 (mean, 123.6).

CONCLUSION

Through this meta-analysis, we found that the C2611T mutation of 23S rRNA is valuable for the molecular diagnostic of moderate-level azithromycin resistance (ML-AzmR) in N. gonorrhoeae, especially when the moderate level is set at 4-128 mg/L. This rapid molecular detection method can be used for the rapid identification of ML-AzmR isolates in the clinic.

A community-driven resource for genomic epidemiology and antimicrobial resistance prediction of Neisseria gonorrhoeae at Pathogenwatch

BACKGROUND

Antimicrobial-resistant (AMR) Neisseria gonorrhoeae is an urgent threat to public health, as strains resistant to at least one of the two last-line antibiotics used in empiric therapy of gonorrhoea, ceftriaxone and azithromycin, have spread internationally. Whole genome sequencing (WGS) data can be used to identify new AMR clones and transmission networks and inform the development of point-of-care tests for antimicrobial susceptibility, novel antimicrobials and vaccines. Community-driven tools that provide an easy access to and analysis of genomic and epidemiological data is the way forward for public health surveillance.

METHODS

Here we present a public health-focussed scheme for genomic epidemiology of N. gonorrhoeae at Pathogenwatch ( https://pathogen.watch/ngonorrhoeae ). An international advisory group of experts in epidemiology, public health, genetics and genomics of N. gonorrhoeae was convened to inform on the utility of current and future analytics in the platform. We implement backwards compatibility with MLST, NG-MAST and NG-STAR typing schemes as well as an exhaustive library of genetic AMR determinants linked to a genotypic prediction of resistance to eight antibiotics. A collection of over 12,000 N. gonorrhoeae genome sequences from public archives has been quality-checked, assembled and made public together with available metadata for contextualization.

RESULTS

AMR prediction from genome data revealed specificity values over 99% for azithromycin, ciprofloxacin and ceftriaxone and sensitivity values around 99% for benzylpenicillin and tetracycline. A case study using the Pathogenwatch collection of N. gonorrhoeae public genomes showed the global expansion of an azithromycin-resistant lineage carrying a mosaic mtr over at least the last 10 years, emphasising the power of Pathogenwatch to explore and evaluate genomic epidemiology questions of public health concern.

CONCLUSIONS

The N. gonorrhoeae scheme in Pathogenwatch provides customised bioinformatic pipelines guided by expert opinion that can be adapted to public health agencies and departments with little expertise in bioinformatics and lower-resourced settings with internet connection but limited computational infrastructure. The advisory group will assess and identify ongoing public health needs in the field of gonorrhoea, particularly regarding gonococcal AMR, in order to further enhance utility with modified or new analytic methods.

Associations between antimicrobial susceptibility/resistance of Neisseria gonorrhoeae isolates in European Union/European Economic Area and patients' gender, sexual orientation and anatomical site of infection, 2009-2016

BACKGROUND

The emergence and spread of antimicrobial resistance (AMR) in Neisseria gonorrhoeae, nationally and internationally, is a serious threat to the management and control of gonorrhoea. Limited and conflicting data regarding the epidemiological drivers of gonococcal AMR internationally have been published. We examined the antimicrobial susceptibility/resistance of gonococcal isolates (n = 15,803) collected across 27 European Union/European Economic Area (EU/EEA) countries in 2009-2016, in conjunction to epidemiological and clinical data of the corresponding patients, to elucidate associations between antimicrobial susceptibility/resistance and patients' gender, sexual orientation and anatomical site of infection.

METHODS

In total, 15,803 N. gonorrhoeae isolates from the European Gonococcal Antimicrobial Surveillance Programme (Euro-GASP), 2009-2016, were examined. Associations between gonococcal susceptibility/resistance and patients' gender, sexual orientation and anatomical site of infection were investigated using univariate and multivariate logistic regression analysis. Statistical significance was determined by Pearson χ2-test or Fisher's exact test with two-tailed p-values of < 0.05 indicating significance.

RESULTS

The overall gonococcal resistance from 2009 to 2016 was 51.7% (range during the years: 46.5-63.5%), 7.1% (4.5-13.2%), 4.3% (1.8-8.7%), and 0.2% (0.0-0.5%) to ciprofloxacin, azithromycin, cefixime, and ceftriaxone, respectively. The level of resistance combined with decreased susceptibility to ceftriaxone was 10.2% (5.7-15.5%). Resistance to cefixime and ciprofloxacin, and resistance combined with decreased susceptibility to ceftriaxone were positively associated with urogenital infections and heterosexual males, males with sexual orientation not reported and females (except for ciprofloxacin), i.e. when compared to men-who-have-sex-with-men (MSM). Azithromycin resistance was positively associated with heterosexual males, but no association was significant regarding anatomical site of infection.

CONCLUSIONS

Overall, sexual orientation was the main variable associated with gonococcal AMR. Strongest positive associations were identified with heterosexual patients, particularly males, and not MSM. To provide evidence-based understanding and mitigate gonococcal AMR emergence and spread, associations between antimicrobial susceptibility/resistance and patients' gender, sexual orientation and anatomical site of infection need to be further investigated in different geographic settings. In general, these insights will support identification of groups at increased risk and targeted public health actions such as intensified screening, 3-site testing using molecular diagnostics, sexual contact tracing, and surveillance of treatment failures.

Adaptation to the cervical environment is associated with increased antibiotic susceptibility in Neisseria gonorrhoeae

Neisseria gonorrhoeae is an urgent public health threat due to rapidly increasing incidence and antibiotic resistance. In contrast with the trend of increasing resistance, clinical isolates that have reverted to susceptibility regularly appear, prompting questions about which pressures compete with antibiotics to shape gonococcal evolution. Here, we used genome-wide association to identify loss-of-function (LOF) mutations in the efflux pump mtrCDE operon as a mechanism of increased antibiotic susceptibility and demonstrate that these mutations are overrepresented in cervical relative to urethral isolates. This enrichment holds true for LOF mutations in another efflux pump, farAB, and in urogenitally-adapted versus typical N. meningitidis, providing evidence for a model in which expression of these pumps in the female urogenital tract incurs a fitness cost for pathogenic Neisseria. Overall, our findings highlight the impact of integrating microbial population genomics with host metadata and demonstrate how host environmental pressures can lead to increased antibiotic susceptibility.