Increasing Azithromycin Resistance in Neisseria gonorrhoeae Due to NG-MAST 12302 Clonal Spread in Canada, 2015 to 2018.

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. Neisseria gonorrhoeae 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. We identified 3,447 N. gonorrhoeae with AZI MICs of ≥1 mg/L in Canada, which increased 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. We identified 273 different N. gonorrhoeae multiantigen sequence types (NG-MAST) 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 (differing by ≤5 bp), designated the ST-12302 genogroup, accounting for 65.2% of study isolates which were originally identified in central Canada but spread to other regions by 2018. Genomic analysis indicated that AZIR in Canadian N. gonorrhoeae 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.

Disseminated Gonococcal Infections in Manitoba, Canada: 2013 to 2020.

BACKGROUND: Gonorrhea, when left untreated, can enter the blood and cause disseminated gonococcal infections (DGIs). Disseminated gonococcal infections, which can include dermatitis, tenosynovitis, migratory polyarthralgia, and arthritis, have been increasing in Manitoba (MB), Canada, since 2013. Endocarditis, a rare DGI, was identified in 3 MB patients in 2018 and 2019. METHODS: Antimicrobial resistance, molecular types, and resistance-associated mutations were determined for MB DGI isolates (n = 103) identified from 2013 to 2020 using phenotypic and genotypic methods. Neisseria gonorrhoeae multiantigen sequence typing (NG-MAST) of residual nucleic acid amplification testing samples (n = 13) from 2019 and 2020 were also determined. RESULTS: The increase in DGI in MB in 2019 and 2020 was due to the NG-MAST 11508 molecular type with porB -2206, a persistent PorB protein structure type "A" allele. These isolates had low-level resistance to erythromycin and tetracycline. CONCLUSIONS: Molecular surveillance of gonorrhea and, in particular, gonococcal strains resulting in DGI is imperative to monitor clonal transmission within populations. These data can be used to alert public health of emerging issues and support public health interventions.

Molecular Surveillance and Prediction of Antimicrobial Resistance of Neisseria gonorrhoeae in Northern Alberta, Canada, 2015 to 2018.

BACKGROUND: The aims of this study was to describe molecular surveillance of Neisseria gonorrhoeae in the North Zone of Alberta (NZ) and to determine its value in predicting antimicrobial resistance. METHODS: Sequence types (STs) and single-nucleotide polymorphism (SNP) assays were performed on nucleic acid amplification testing (NAAT) samples. Sequence types of NAATs were matched to ST of cultures from across Alberta. Antimicrobial resistance prediction of NAATs for cephalosporins, azithromycin, and ciprofloxacin using SNP was compared with matching ST culture results using agar dilution and whole-genome sequencing. RESULTS: Of 2755 eligible specimens (2492 cases), 61.9% (1646 specimens) were sent for sequence typing, identifying 196 unique ST. Antimicrobial resistance data for 1307 additional cases were available using matching cultures. Decreased susceptibility (DS) to antimicrobials used for gonorrhea treatment was rare in the NZ; according to the SNP assay, none of the specimens had predicted DS to cephalosporins or azithromycin resistance. However, of the NZ NAAT samples tested in this study, 10.7% (131 of 1220) were predicted to have intermediate cephalosporin minimum inhibitory concentrations and 9.6% (115 of 1204) were resistant to ciprofloxacin. Based on cultures, the proportions of resistance in all of Alberta were as follows: DS to cephalosporins, 0.6% (20 of 3373); DS to intermediate cephalosporin, 16.9% (570 of 3373); azithromycin resistance, 1.2% (41 of 3373); and ciprofloxacin resistance, 32.2% (1087 of 3373). CONCLUSIONS: Our results highlight our ability to use culture-independent methods to predict antimicrobial resistance in N. gonorrhoeae.

Equations To Predict Antimicrobial MICs in Neisseria gonorrhoeae Using Molecular Antimicrobial Resistance Determinants.

The emergence of Neisseria gonorrhoeae strains that are resistant to azithromycin and extended-spectrum cephalosporins represents a public health threat, that of untreatable gonorrhea infections. Multivariate regression modeling was used to determine the contributions of molecular antimicrobial resistance determinants to the overall antimicrobial MICs for ceftriaxone, cefixime, azithromycin, tetracycline, ciprofloxacin, and penicillin. A training data set consisting of 1,280 N. gonorrhoeae strains was used to generate regression equations which were then applied to validation data sets of Canadian (n = 1,095) and international (n = 431) strains. The predicted MICs for extended-spectrum cephalosporins (ceftriaxone and cefixime) were fully explained by 5 amino acid substitutions in PenA, A311V, A501P/T/V, N513Y, A517G, and G543S; the presence of a disrupted mtrR promoter; and the PorB G120 and PonA L421P mutations. The correlation of predicted MICs within one doubling dilution to phenotypically determined MICs of the Canadian validation data set was 95.0% for ceftriaxone, 95.6% for cefixime, 91.4% for azithromycin, 98.2% for tetracycline, 90.4% for ciprofloxacin, and 92.3% for penicillin, with an overall sensitivity of 99.9% and specificity of 97.1%. The correlations of predicted MIC values to the phenotypically determined MICs were similar to those from phenotype MIC-only comparison studies. The ability to acquire detailed antimicrobial resistance information directly from molecular data will facilitate the transition to whole-genome sequencing analysis from phenotypic testing and can fill the surveillance gap in an era of increased reliance on nucleic acid assay testing (NAAT) diagnostics to better monitor the dynamics of N. gonorrhoeae.

Quality assurance for antimicrobial susceptibility testing of Neisseria gonorrhoeae in Latin American and Caribbean countries, 2013-2015.

OBJECTIVES: A Neisseria gonorrhoeae antimicrobial susceptibility quality control comparison programme was re-established in Latin America and the Caribbean to ensure antimicrobial susceptibility data produced from the region are comparable nationally and internationally. METHODS: Three panels, consisting of N. gonorrhoeae isolates comprising reference strains and other characterised isolates were sent to 11 participating laboratories between 2013 and 2015. Antimicrobial susceptibilities for these isolates were determined using agar dilution, Etest or disc diffusion methods. Modal minimum inhibitory concentrations (MICs) for each panel isolate/antibiotic combination were calculated. The guidelines of the Clinical and Laboratory Standards Institute were used for interpretations of antimicrobial susceptibility. The agreement of MICs with the modal MICs was determined for each of the participating laboratories as well as for each of the antibiotics tested. RESULTS: Five of 11 laboratories that participated in at least one panel had an overall average agreement between participants' MIC results and modal MICs of >90%. For other laboratories, agreements ranged from 60.0% to 82.4%. The proportion of agreement between interpretations for all the antibiotics, except penicillin and tetracycline, was >90%. The percentages of agreement between MIC results and their modes for erythromycin, spectinomycin, cefixime and azithromycin were >90%. Tetracycline, ceftriaxone and ciprofloxacin agreement ranged from 84.5% to 89.1%, while penicillin had 78.8% agreement between MICs and modal MICs. CONCLUSIONS: The participating laboratories had acceptable results, similar to other international quality assurance programmes. It is important to ensure continuation of the International Gonococcal Antimicrobial Susceptibility Quality Control Comparison Programme to ensure that participants can identify and correct any problems in antimicrobial susceptibility testing for N. gonorrhoeae as they arise and continue to generate reproducible and reliable data.

Quality Assurance for Antimicrobial Susceptibility Testing of Neisseria gonorrhoeae in Canada, 2003 to 2012.

Data from the Canadian National Gonococcal Antimicrobial Susceptibility Comparison Program, including results from 25 proficiency panels distributed between 2003 and 2012, were analyzed. The average MIC agreement between the participating laboratories ranged from 85.6% to 98.8% over the 10-year period, with the interpretation agreement ranging from 85.7% to 98.1%.

Antimicrobial susceptibilities and distribution of sequence types of Neisseria gonorrhoeae isolates in Canada: 2010.

The monitoring of antimicrobial susceptibilities in Neisseria gonorrhoeae isolates and characterization of N. gonorrhoeae multiantigen sequence types (NG-MAST, ST) provide important surveillance data as resistance rates continue to rise. A total of 2970 N. gonorrhoeae isolates were collected by Canadian provincial public health laboratories in 2010, and 1233 were submitted to the National Microbiology Laboratory for testing. The NG-MAST and minimum inhibitory concentration (MIC) by agar dilution were determined for each isolate. Of the 2970 isolates, 25.1% were resistant to penicillin, 34.6% resistant to tetracycline, 31.5% resistant to erythromycin, 35.9% resistant to ciprofloxacin, and 1.2% resistant to azithromycin. Decreased susceptibility to cefixime (MIC ≥ 0.25 mg/L) and ceftriaxone (MIC ≥ 0.125 mg/L) was identified in 3.2% and 7.3% of the isolates, respectively. The most common STs found in Canada were ST1407 (13.3%), ST3150 (11.3%), and ST3158 (9.0%), with 249 different STs identified among the isolates. Within the ST1407 group, 19.5% and 43.3% isolates have decreased susceptibility to cefixime and ceftriaxone, respectively. ST1407, the most prevalent NG-MAST in Canada in 2010, has been associated with high-level ceftriaxone MICs and with cefixime treatment failure cases worldwide. Identification and monitoring of STs and corresponding antimicrobial resistance profiles may be useful in surveillance programs and be used to inform public health actions.

Emergence and characterization of Neisseria gonorrhoeae isolates with decreased susceptibilities to ceftriaxone and cefixime in Canada: 2001-2010.

BACKGROUND: Globally, Neisseria gonorrhoeae antimicrobial resistance has been increasing, and in particular, reports of isolates with reduced susceptibility to third-generation cephalosporins have surfaced. We examined the phenotypic and genetic characteristics of 155 N. gonorrhoeae isolates with decreased susceptibilities to third-generation cephalosporins isolated in Canada between 2001 and mid-2010. METHODS: Minimum inhibitory concentrations (MICs) were determined by agar dilution on N. gonorrhoeae isolates, and those displaying elevated MICs to cefixime (MIC = 0.25 µg/mL and 0.5 µg/mL) and ceftriaxone (MIC = 0.125 µg/mL and 0.25 µg/mL) were examined using N. gonorrhoeae multiantigen sequence typing (NG-MAST) and sequencing of resistance determinants associated with decreased cephalosporin susceptibilities (penA, mtrR, ponA, porB1b (penB alteration). RESULTS: Between 2001 and 2010, there has been a shift in the modal MICs from 0.016 to 0.125 µg/mL for cefixime and from 0.016 to 0.063 µg/mL for ceftriaxone. Thirty-seven different sequence types (STs) were identified among the isolates using N. gonorrhoeae multiantigen sequence typing; ST3158, ST225, and ST1407 were most prevalent at 25.9%, 19.4%, and 14.8%, respectively. The penA mosaic was present in 60% of the isolates, with the most common penA mosaic types XXXII and X identified at 51.0% and 7.7%, respectively, whereas the nonmosaic penA type XII was identified in 36.8% of the isolates. CONCLUSIONS: In Canada, N. gonorrhoeae isolates with decreased susceptibilities to third-generation cephalosporins have increased over the years. The alterations in penA, mtrR, and porB1b (penB alteration) are important determinants identified in these isolates. The most common STs identified among these Canadian isolates have also been reported worldwide.

Identification of prolyliminopeptidase-negative Neisseria gonorrhoeae strains in Canada.

Neisseria gonorrhoeae strains that fail to produce the enzyme prolyliminopeptidase have been identified in Canada. Commercial test panels use prolyliminopeptidase activity for identification and to avoid the misdiagnosis of gonorrhea, at least 2 distinct methods for the confirmatory identification of N. gonorrhoeae is imperative.

Serological diagnosis of syphilis: enzyme-linked immunosorbent assay to measure antibodies to individual recombinant Treponema pallidum antigens.

We standardized an indirect ELISA for measurement of serum antibody levels to four individual treponemal recombinant proteins that have been commonly used in a number of commercial EIAs, mostly as a mixture of antigens. When tested with 127 syphilis-negative and 37 secondary syphilis sera, ELISA O.D.s obtained for each of the four antigens clearly distinguished between these two groups of samples. Sensitivity and specificity of 100% was obtained with the current set of samples. Further evaluations with sera from different stages of syphilis can help to define the applications of this ELISA test for each of the four antigens studied.

Serological diagnosis of syphilis: comparison of the Trep-Chek IgG enzyme immunoassay with other screening and confirmatory tests.

The Trep-Chek IgG Enzyme Immunoassay (Trep-Chek IgG EIA) was evaluated with 604 serum specimens submitted for syphilis serology from patients across Canada against a battery of conventional syphilis serology tests, including the Rapid Plasma Reagin (RPR) test, the Venereal Disease Research Laboratory (VDRL) test, the Treponema pallidum passive particle agglutination (TP-PA) test, the fluorescent treponemal antibody absorption (FTA-ABS) test, and the newer confirmatory test, Innogenetics INNO-LIA. On the basis of a consensus result derived from these serologic tests, 34 specimens were found to be syphilis-positive (28 active and six past infections), and 570 were syphilis-negative (including 12 biological false positives). When the test results on this set of samples were compared to those obtained with the conventional tests RPR, VDRL, TP-PA, and FTA-ABS, the sensitivity and specificity of the Trep-Chek IgG EIA were found to be 85.3% and 95.6%, respectively. Without further evaluation, we do not recommend use of the Trep-Chek IgG EIA as a stand-alone test for either screening or confirmatory syphilis serology.