Trends in antimicrobial susceptibility for azithromycin and ceftriaxone in Neisseria gonorrhoeae isolates in Amsterdam, the Netherlands, between 2012 and 2015

Correlates of Neisseria gonorrhoeae antimicrobial resistance: cross-sectional results from an open cohort sentinel surveillance network in Québec, Canada, 2016-2019

OBJECTIVES

To examine correlates of Neisseria gonorrhoeae antimicrobial resistance (AMR) to first-line antimicrobials (azithromycin, cefixime and ceftriaxone).

DESIGN AND SETTING

The sentinel surveillance network is an open cohort of gonococcal infection cases from Québec, Canada. Cross-sectional results are reported herein.

PARTICIPANTS

Between 1 January 2016 and 31 December 2019, data from 886 individuals accounting for 941 gonorrhoea cases were included.

METHODS

Epidemiological and clinical data were collected using an auto-administered questionnaire, direct case interviews and chart reviews. Antimicrobial susceptibility testing was performed using the agar dilution method. Generalised estimating equations were used for regression.

RESULTS

The prevalence of azithromycin resistance with a minimal inhibitory concentration (MIC) of ≥2 mg/L was 21.3%. In 2016, men who have sex with men were more likely to be infected with an azithromycin-resistant N. gonorrhoeae isolate (adjusted prevalence ratio (aPR)=4.73, 95% CI 1.48 to 15.19) or with an isolate with increased third-generation cephalosporin (3GC) MIC (aPR=5.32, 95% CI 1.17 to 24.11 for cefixime (MIC≥0.06 mg/L) and aPR=4.38, 95% CI 1.53 to 12.54 for ceftriaxone (MIC≥0.03 mg/L)). However, these associations were not maintained between 2017 and 2019, with increased MIC observed in men who have sex exclusively with women and women. Overall, azithromycin resistance was significantly more likely in cases who self-reported HIV infection (aPR=1.65, 95% CI 1.00 to 2.71). Cefixime increased MIC were more likely in individuals 25-34 years old (aPR=2.23, 95% CI 1.18 to 4.21). Cefixime and ceftriaxone increased MIC were both more likely in cases who reported ≥5 sexual partners (cefixime: aPR=2.10, 95% CI 1.34 to 3.27 and ceftriaxone: aPR=1.62, 95% CI 1.14 to 2.30).

CONCLUSION

Significant correlates of N. gonorrhoeae AMR to first-line antimicrobials were observed. Antimicrobial stewardship may be particularly important for 3GC. Active monitoring and interventions are critical for 3GC non-susceptible strains, especially considering the very low prevalence in Québec.

Global status of Azithromycin and Erythromycin Resistance Rates in Neisseria gonorrhoeae: A Systematic Review and Meta-analysis

Background: The widespread development of antibiotic resistance or decreased susceptibility in Neisseria gonorrhoeae (NG) infection is a global and significant human public health issue. Objectives: Therefore, this meta-analysis aimed to estimate worldwide resistance rates of NG to the azithromycin and erythromycin according to years, regions, and antimicrobial susceptibility testing (AST). Methods: We systematically searched the published studies in PubMed, Scopus, and Embase from 1988 to 2021. All analyses were conducted using Stata software. Results: The 134 reports included in the meta-analysis were performed in 51 countries and examined 165,172 NG isolates. Most of the included studies were from Asia (50 studies) and Europe (46 studies). In the metadata, the global prevalence over the past 30 years were 6% for azithromycin and 48% for erythromycin. There was substantial change in the prevalence of macrolides NG resistance over time (P <0.01). In this metadata, among 58 countries reporting resistance data for azithromycin, 17 (29.3%) countries reported that >5% of specimens had azithromycin resistance. Conclusions: The implications of this study emphasize the rigorous or improved antimicrobial stewardship, early diagnosis, contact tracing, and enhanced intensive global surveillance system are crucial for control of further spreading of gonococcal emergence of antimicrobial resistance (AMR).

Mechanism of action, resistance, synergism, and clinical implications of azithromycin

Background

Azithromycin (AZM), sold under the name Zithromax, is classified as a macrolide. It has many benefits due to its immunomodulatory, anti‐inflammatory, and antibacterial effects. This review aims to study different clinical and biochemisterial aspects and properties of this drug which has a priority based on literature published worldwide.

Methods

Several databases including Web of Science, Google Scholar, PubMed, and Scopus were searched to obtain the relevant studies.

Results

AZM mechanism of action including the inhibition of bacterial protein synthesis, inhibition of proinflammatory cytokine production, inhibition of neutrophil infestation, and macrophage polarization alteration, gives it the ability to act against a wide range of microorganisms. Resistant organisms are spreading and being developed because of the irrational use of the drug in the case of dose and duration. AZM shows synergistic effects with other drugs against a variety of organisms. This macrolide is considered a valuable antimicrobial agent because of its use as a treatment for a vast range of diseases such as asthma, bronchiolitis, COPD, cystic fibrosis, enteric infections, STIs, and periodontal infections.

Conclusions

Our study shows an increasing global prevalence of AZM resistance. Thus, synergistic combinations are recommended to treat different pathogens. Moreover, continuous monitoring of AZM resistance by registry centers and the development of more rapid diagnostic assays are urgently needed.

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

OBJECTIVES

To investigate the relationship between MIC and clinical outcome in a randomized controlled trial that compared gentamicin 240 mg plus azithromycin 1 g with ceftriaxone 500 mg plus azithromycin 1 g. MIC analysis was performed on Neisseria gonorrhoeae isolates from all participants who were culture positive before they received treatment.

METHODS

Viable gonococcal cultures were available from 279 participants, of whom 145 received ceftriaxone/azithromycin and 134 received gentamicin/azithromycin. Four participants (6 isolates) and 14 participants (17 isolates) did not clear infection in the ceftriaxone/azithromycin and gentamicin/azithromycin arms, respectively. MICs were determined by Etest on GC agar base with 1% Vitox. The geometric mean MICs of azithromycin, ceftriaxone and gentamicin were compared using logistic and linear regression according to treatment received and N. gonorrhoeae clearance.

RESULTS

As the azithromycin MIC increased, gentamicin/azithromycin treatment was less effective than ceftriaxone/azithromycin at clearing N. gonorrhoeae. There was a higher geometric mean MIC of azithromycin for isolates from participants who had received gentamicin/azithromycin and did not clear infection compared with those who did clear infection [ratio 1.95 (95% CI 1.28-2.97)], but the use of categorical MIC breakpoints did not accurately predict the treatment response. The geometric mean MIC of azithromycin was higher in isolates from the pharynx compared with genital isolates.

CONCLUSIONS

We found that categorical resistance to azithromycin or ceftriaxone in vitro, and higher gentamicin MICs in the absence of breakpoints, were poorly predictive of treatment failure.

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.

Surveillance and molecular epidemiology of Neisseria gonorrhoeae isolates in Shenzhen, China, 2010-2017

OBJECTIVES

The development and emergence of antimicrobial resistance in Neisseria gonorrhoeae (NG) have become a major public-health problem worldwide. This study aimed to analyse the antimicrobial susceptibility and molecular characteristics of NG isolates in Shenzhen, China.

METHODS

A total of 1282 NG isolates were consecutively collected between 2010 and 2017. Patient demographic information was also collected. MICs of ceftriaxone, spectinomycin, ciprofloxacin, azithromycin and penicillin were determined by agar dilution. Isolates were genotyped using N. gonorrhoeae multi-antigen sequence typing (NG-MAST).

RESULTS

Among the isolates, 97.4% were resistant to ciprofloxacin and 68.2% to penicillin. Moreover, 5.0% showed decreased susceptibility to ceftriaxone (CRO^D) and 17.3% were resistant to azithromycin (AZM-R); 1.3% were simultaneously CRO^D and AZM-R. All isolates were susceptible to spectinomycin. Increasing ceftriaxone MICs were found from 2010 to 2017. A total of 427 sequence types (STs) and 68 genogroups were identified from 724 isolates. ST5061, ST3741 and ST1766 were observed across the study years. ST14638 (n = 3) was predominant among 32 CRO^D isolates. Prevalent STs were ST5061 (n = 6), ST1866 (n = 5) and ST11133 (n = 5) among 96 AZM-R isolates.

CONCLUSIONS

A high prevalence of isolates resistant to ciprofloxacin and penicillin was found in this study. Azithromycin, one antimicrobial of dual antimicrobial therapy recommended by the WHO, showed a high prevalence of resistance. The other, ceftriaxone, can be used continuously in this region owing to lower resistance levels. However, the emergence of CRO^D and decreasing susceptibility to ceftriaxone indicate that continuous antimicrobial resistance surveillance is essential.

Azithromycin resistant gonococci: a literature review

OBJECTIVE

Gonorrhea is the second most common sexually transmitted bacterial infection (STI) next to Chlamydia. Untreated cases could results in major complications like pelvic inflammatory disease (PID), ectopic pregnancy, infertility, miscarriage, fetal death and congenital infections. Gonorrhea has been treated with antibiotics for more than eight decades. However, the emergence and spread of antimicrobial resistance (AMR) in gonococcus seriously compromises the management of the disease. The aim of this review was to describe the current developments in the field of azithromycin resistant gonococci.

METHODS

Literatures published in English in the last 10 years were retrieved from PubMed, SCOPUS, Google scholar, Cochrane library and the Google databases using relevant searching terms.

RESULTS

Gonococcus is capable of using a number of strategies to confer resistance as the bacterium has an extraordinary capacity to alter its genome. So far the accumulated data on the field showed that the world is heading towards a pandemic of extensively drug-resistant (XDR) gonococcus which is now seems to be evolving into a true "superbug". Hence, in the near future gonorrhea may become untreatable on the international basis unless new drugs become available. An antibiotic resistance in gonococcus has been noted beginning in 1940s against sulfonamides. Since then, resistance has rapidly emerged to penicillins, tetracyclines, macrolides, fluoroquinolones, and cephalosporins. Currently, in most nations, the injectable extended-spectrum cephalosporin (ESC), i.e. ceftriaxone based therapy is the only remaining option for gonorrhea. Based on the WHO and the US-CDC recommendations, countries are increasingly using a combination of cephalosporin and azithromycin for the treatment of gonorrhoea. Azithromycin revolutionized gonoccocal therapy as it shortened treatment time by more than half from 7 to 14 days and improved patient compliance due to high tissue levels and long half-life. However, constantly emerging reports from different parts of the globe showed that N. gonorrhoeae is developing significant level of resistance against azithromycin, and so far more than 33% level of resistance was reported. Two strategies have been commonly implicated in gonococcal resistance against azithromycin: over expression of an efflux pump (due to mutations at mtrR coding region) and decreased antimicrobial affinity (due to mutations in genes encoding the 23S ribosomal subunit).

CONCLUSIONS

With no alternative antimicrobial treatment options for gonorrhoea and only a few new drugs in the development pipeline, it is necessary to monitor drug resistance and optimize treatment regimens regularly. Moreover, investigations for novel drugs should be wired.

Trends and determinants of antimicrobial susceptibility of Neisseria gonorrhoeae in the Netherlands, 2007 to 2015

Neisseria gonorrhoeae antibiotic resistance surveillance is important to maintain adequate treatment. We analysed 2007–15 data from the Gonococcal Resistance to Antimicrobials Surveillance (GRAS), which currently includes 19 of 25 sexually transmitted infection (STI) centres in the Netherlands. Methods: From each patient with a gonorrhoea culture, the minimum inhibitory concentration (MIC) for several antibiotics was determined. Time trends were assessed by geometric means and linear regression of logarithmic MIC. Determinants for decreased susceptibility to ceftriaxone (MIC > 0.032 mg/L) and resistance to cefotaxime (MIC > 0.125 mg/L) and azithromycin (MIC > 0.5 mg/L) were assessed using stratified logistic regression. Results: 11,768 isolates were analysed. No ceftriaxone resistance was found. In 2015, 27 of 1,425 isolates (1.9%) were resistant to cefotaxime and 176 of 1,623 (10.9%) to azithromycin. Ceftriaxone susceptibility showed no trend (p = 0.96) during the study period, but cefotaxime MIC decreased (p < 0.0001) and azithromycin MIC increased (p < 0.0001) significantly. Concerning ceftriaxone, isolates of men who have sex with men (MSM) from 2013 (p = 0.0005) and 2014 (p = 0.0004) were significantly associated with decreased susceptibility. Significant determinants for cefotaxime resistance were having ≥ 6 partners for women (p = 0.0006). For azithromycin,isolates from MSM collected in 2012 (p = 0.0035), 2013 (p = 0.012), and 2014 (p = 0.013), or from non-Dutch (p < 0.0001) or older (≥ 35 years; p = 0.01) MSM were significantly associated with susceptibility. Resistance in heterosexual men was significantly associated with being ≥ 25 years-old (p = 0.0049) or having 3–5 partners (p = 0.01). Conclusions: No ceftriaxone resistance was found, but azithromycin MIC increased in 2007–15. Resistance determinants could help with focused intervention strategies.

Trends in antimicrobial management of gonorrhoea by general practitioners in Amsterdam, the Netherlands, between 2010 and 2016: a cross-sectional study

Background

Sexually transmitted infections (STI) caused by multidrug resistant Neisseria gonorrhoea are an emerging threat to global health. In the Netherlands, the general practitioner (GP) provides the major part of STI care. In 2013 an update of the Dutch guideline was published, recommending a single dose of intramuscular ceftriaxone as treatment for gonorrhoea infections. Data from a Dutch General Practitioner research database was used to investigate the guideline implementation for the treatment of gonorrhoea. A survey was conducted to gain more insight in GPs experiences with the recommended intramuscular therapy.

Methods

Data on STI-related episodes and STI-diagnoses for gonorrhoea, based on ICPC codes were obtained from the electronic medical records (EMRs) from 35 GPs in Amsterdam for the years 2010 to 2016. Questionnaires regarding the treatment preferences were sent to GPs participating in the research network database.

Results

The number of gonorrhoea cases treated with first choice therapy increased from 81% in 2010 (intramuscular cefotaxime or ceftriaxone) to 93% in 2015 (only cefttriaxone). The number of ceftriaxone prescriptions increased substantially from 30% in 2010 to 93% in 2015. GPs preferred a single intramuscular shot of a third-generation cephalosporin above multiple oral doses of other antibiotics.

Conclusions

The results demonstrate a successful shift in the antimicrobial management of gonorrhoea infections to ceftriaxone monotherapy according to the national guideline. GPs in this higher prevalence area in Amsterdam reported limited barriers in the intramuscular administration of third-generation cephalosporins.

Electronic supplementary material

The online version of this article (10.1186/s12875-018-0900-9) contains supplementary material, which is available to authorized users.

Antimicrobial resistance and molecular epidemiology using whole-genome sequencing of Neisseria gonorrhoeae in Ireland, 2014-2016: focus on extended-spectrum cephalosporins and azithromycin

High-level resistance and treatment failures with ceftriaxone and azithromycin, the first-line agents for gonorrhoea treatment are reported and antimicrobial-resistant Neisseria gonorrhoeae is an urgent public health threat. Our aims were to determine antimicrobial resistance rates, resistance determinants and phylogeny of N. gonorrhoeae in Ireland, 2014-2016. Overall, 609 isolates from four University Hospitals were tested for susceptibility to extended-spectrum cephalosporins (ESCs) and azithromycin by the MIC Test Strips. Forty-three isolates were whole-genome sequenced based on elevated MICs. The resistance rate to ceftriaxone, cefixime, cefotaxime and azithromycin was 0, 1, 2.1 and 19%, respectively. Seven high-level azithromycin-resistant (HLAzi-R) isolates were identified, all susceptible to ceftriaxone. Mosaic penA alleles XXXIV, X and non-mosaic XIII, and G120K plus A121N/D/G (PorB1b), H105Y (MtrR) and A deletion (mtrR promoter) mutations, were associated with elevated ESC MICs. A2059G and C2611T mutations in 23S rRNA were associated with HLAzi-R and azithromycin MICs of 4-32 mg/L, respectively. The 43 whole-genome sequenced isolates belonged to 31 NG-MAST STs. All HLAzi-R isolates belonged to MLST ST1580 and some clonal clustering was observed; however, the isolates differed significantly from the published HLAzi-R isolates from the ongoing UK outbreak. There is good correlation between previously described genetic antimicrobial resistance determinants and phenotypic susceptibility categories for ESCs and azithromycin in N. gonorrhoeae. This work highlights the advantages and potential of whole-genome sequencing to be applied at scale in the surveillance of antibiotic resistant strains of N. gonorrhoeae, both locally and internationally.

Epidemiological, behavioural, and clinical factors associated with antimicrobial-resistant gonorrhoea: a review

Antimicrobial-resistant Neisseria gonorrhoeae is a global public health problem in the 21st century. N. gonorrhoeae has developed resistance to all classes of antibiotics used for empirical treatment, and clinical treatment failure caused by extensively resistant strains has been reported. Identifying specific factors associated with an increased risk of antimicrobial-resistant N. gonorrhoeae might help to develop strategies to improve antimicrobial stewardship. In this review, we describe the findings of 24 studies, published between 1989 and 2017, that examined epidemiological, behavioural, and clinical factors and their associations with a range of antimicrobial agents used to treat gonorrhoea. Antimicrobial-resistant N. gonorrhoeae is more common in older than younger adults and in men who have sex with men compared with heterosexual men and women. Antimicrobial-resistant N. gonorrhoeae is less common in some black minority and Aboriginal ethnic groups than in the majority white population in high-income countries. The factors associated with antimicrobial-resistant gonorrhoea are not necessarily those associated with a higher risk of gonorrhoea.

Susceptibility of Neisseria gonorrhoeae to azithromycin and ceftriaxone in China: A retrospective study of national surveillance data from 2013 to 2016

BACKGROUND

Gonorrhea remains one of the most common sexually transmitted diseases worldwide. Successful treatment has been hampered by emerging resistance to each of the antibiotics recommended as first-line therapies. We retrospectively analyzed the susceptibility of gonorrhea to azithromycin and ceftriaxone using data from the China Gonococcal Resistance Surveillance Programme (China-GRSP) in order to provide evidence for updating the treatment recommendations in China.

METHODS AND FINDINGS

In this study, we included 3,849 isolates collected from patients with a confirmed positive Neisseria gonorrhoeae (N. gonorrhoeae) culture at clinic visits during the period of 1 January 2013 through 31 December 2016 in 7 provinces. Antimicrobial susceptibility testing of gonorrhea isolates using agar dilution was conducted to determine minimum inhibitory concentration (MIC). Resistance to azithromycin (RTA) was defined as MIC ≥ 1.0 mg/l, and decreased susceptibility to ceftriaxone (DSC) was defined as MIC ≥ 0.125 mg/l. The prevalence of isolates with RTA was 18.6% (710/3,827; 95% CI 17.4%-19.8%). The percentage of patients with DSC fluctuated between 9.7% and 12.2% over this period. The overall prevalence of isolates with both RTA and DSC was 2.3% (87/3,827; 95% CI 1.9%-2.8%) and it increased from 1.9% in 2013 to 3.3% in 2016 (chi-squared test for trend, P = 0.03). Study limitations include the retrospective study design and potential biases in the sample, which may overrepresent men with symptomatic infection, coastal residents, and people reporting as heterosexual.

CONCLUSIONS

To our knowledge, this is the first national study on susceptibility of N. gonorrhoeae to azithromycin and ceftriaxone in China. Our findings indicate high rates of RTA and DSC from 2013 to 2016. Although dual therapy with azithromycin and ceftriaxone has been recommended by WHO and many countries to treat gonorrhea, reevaluation of this therapy is needed prior to its introduction in China.

Partner notification and partner treatment for chlamydia: attitude and practice of general practitioners in the Netherlands; a landscape analysis

BACKGROUND

Chlamydia prevalence remains high despite scaling-up control efforts. Transmission is not effectively interrupted without partner notification (PN) and (timely) partner treatment (PT). In the Netherlands, the follow-up of partners is not standardized and may depend on GPs' time and priorities. We investigated current practice and attitude of GPs towards PN and PT to determine the potential for Patient-Initiated Partner Treatment, which is legally not supported yet.

METHODS

Multiple data-sources were combined for a landscape analysis. Quantitative data on (potential) PT were obtained from prescriptions in the national pharmacy register (2004-2014) and electronic patient data from NIVEL-Primary Care Database (PCD) and from STI consultations in a subgroup of sentinel practices therein. Furthermore, we collected information on current practice via two short questionnaires at a national GP conference and obtained insight into GPs' attitudes towards PN/PT in a vignette study among GPs partaking in NIVEL-PCD.

RESULTS

Prescription data showed Azithromycin double dosages in 1-2% of cases in the pharmacy register (37.000 per year); probable chlamydia-specific repeated prescriptions or double dosages of other antibiotics in NIVEL-PCD (115/1078) could not be interpreted as PT for chlamydia with certainty. STI consultation data revealed direct PT in 6/100 cases, via partner prescription or double doses. In the questionnaires the large majority of GPs (>95% of 1411) reported to discuss PN of current and ex-partner(s) with chlamydia patients. Direct PT was indicated as most common method by 4% of 271 GPs overall and by 12% for partners registered in the same practice. Usually, GPs leave further steps to the patients (83%), advising patients to tell partners to get tested (56%) or treated (28%). In the vignette study, 16-20% of 268 GPs indicated willingness to provide direct PT, depending on patient/partner profile, more (24-45%) if patients would have the chance to notify their partner first.

CONCLUSION

GPs in the Netherlands already treat some partners of chlamydia cases directly, especially partners registered in the same practice. Follow-up of partner notification and treatment in general practice needs more attention. GPs may be open to implement PIPT more often, provided there are clear guidelines to arrange this legally and practically.

Antibiotic Susceptibility Monitoring of Neisseria gonorrhoeae in Bacolod City, Philippines

A local study was conducted to monitor the antibiotic susceptibility of N. gonorrhoeae in Bacolod City, Philippines. A total of 88 isolates were taken during the period of 1 January 2015 to 30 June 2017, from male patients ages 12 to 72 years. The highest incidence of gonorrhea infection was in the group aged 20⁻24 years (34.09%). The susceptibility pattern to antibiotics was as follows: ceftriaxone 100%, cefixime 82.6%, spectinomycin 92.1%, ciprofloxacin 4.9%, tetracycline 5.1%, and penicillin G with 0%. All isolates were noted to produce beta-lactamase, which can be attributed to plasmid-mediated penicillin resistance. These findings indicate that the resistance rates of N. gonorrhoeae to most commonly-used antibiotics are increasing, and that ceftriaxone remains an effective antibiotic in treating gonorrhea infections locally.

A Case-Control Study of Molecular Epidemiology in Relation to Azithromycin Resistance in Neisseria gonorrhoeae Isolates Collected in Amsterdam, the Netherlands, between 2008 and 2015

Neisseria gonorrhoeae resistance to ceftriaxone and azithromycin is increasing, which threatens the recommended dual therapy. We used molecular epidemiology to identify N. gonorrhoeae clusters and associations with azithromycin resistance in Amsterdam, the Netherlands. N. gonorrhoeae isolates (n = 143) were selected from patients visiting the Amsterdam STI Outpatient Clinic from January 2008 through September 2015. We included all 69 azithromycin-resistant isolates (MIC ≥ 2.0 mg/liter) and 74 frequency-matched susceptible controls (MIC ≤ 0.25 mg/liter). The methods used were 23S rRNA and mtrR sequencing, N. gonorrhoeae multiantigen sequence typing (NG-MAST), N. gonorrhoeae multilocus variable-number tandem-repeat analysis (NG-MLVA), and a specific PCR to detect mosaic penA genes. A hierarchical cluster analysis of NG-MLVA related to resistance and epidemiological characteristics was performed. Azithromycin-resistant isolates had C2611T mutations in 23S rRNA (n = 62, 89.9%, P < 0.001) and were NG-MAST genogroup G2992 (P < 0.001), G5108 (P < 0.001), or G359 (P = 0.02) significantly more often than susceptible isolates and were more often part of NG-MLVA clusters (P < 0.001). Two resistant isolates (2.9%) had A2059G mutations, and five (7.3%) had wild-type 23S rRNA. No association between mtrR mutations and azithromycin resistance was found. Twenty-four isolates, including 10 azithromycin-resistant isolates, showed reduced susceptibility to extended-spectrum cephalosporins. Of these, five contained a penA mosaic gene. Four of the five NG-MLVA clusters contained resistant and susceptible isolates. Two clusters consisting mainly of resistant isolates included strains from men who have sex with men and from heterosexual males and females. The co-occurrence of resistant and susceptible strains in NG-MLVA clusters and the frequent occurrence of resistant strains outside of clusters suggest that azithromycin resistance develops independently from the background genome.