Azithromycin and erythromycin resistant Neisseria gonorrhoeae following treatment with azithromycin

Can we use azithromycin eye drops for gonococcal ophthalmia prophylaxis in the United States?

INTRODUCTION

Neonatal ocular prophylaxis with 0.5% erythromycin ophthalmic ointment is mandated by law in many U.S. states despite its lack of efficacy in preventing chlamydial ophthalmia and the low incidence of gonococcal ophthalmia today. The current shortage of 0.5% erythromycin ophthalmic ointment is bringing into question what alternatives exist for neonatal ocular prophylaxis for the prevention of gonococcal ophthalmia. Providers in states with mandates are concerned with the implications of administering intramuscular ceftriaxone to every newborn. Azithromycin eye drops are being considered as an alternative.

AREAS COVERED

This article discusses 1% azithromycin eye drops as an alternative to 0.5% erythromycin ophthalmic ointment. Clinical experience, side effects, resistance, logistics, pharmacokinetics, and pharmacodynamics are considered.

EXPERT OPINION

Azithromycin eye drops are not an appropriate alternative to 0.5% erythromycin ophthalmic ointment for ocular prophylaxis. Prenatal screening and treatment of pregnant women is the most effective way to prevent neonatal ophthalmia. Mandates for universal prophylaxis should be withdrawn to avoid unnecessary medication administration, healthcare costs, and potential harm.

Clinical, biological and genome-wide comparison of carbapenem-resistant Klebsiella pneumoniae with susceptibility transformation to polymyxin B during therapy

OBJECTIVES

The emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP) is a major clinical concern, and polymyxin B (PMB) is a 'last resort' antibiotic for its treatment. Understanding the effects of drug susceptibility transformation in CRKP-infected patients undergoing PMB treatment would be beneficial to optimize PMB treatment strategies.

METHODS

We retrospectively collected data from patients infected with CRKP and treated with PMB from January 2018 to December 2020. CRKPs were collected before and after PMB therapy, and patients were classified into the 'transformation' group (TG) and 'non-transformation' group (NTG) by the shift of susceptibility to PMB. We compared clinical characteristics between these groups, and further analysed the phenotypic and genome variation of CRKP after PMB susceptibility transformation.

RESULTS

A total of 160 patients (37 in the TG and 123 in the NTG) were included in this study. The duration of PMB treatment before PMB-resistant K. pneumoniae (PRKP) appearance in TG was even longer than the whole duration of PMB treatment in NTG (8 [8] vs. 7 [6] days; p 0.0496). Compared with isogenic PMB-susceptible K. pneumoniae (PSKP), most PRKP strains had missense mutations in mgrB (12 isolates), yciC (10 isolates) and pmrB (7 isolates). The competition index of 82.4% (28/34) of PRKP/PSKP pairs was <67.6% (23/34), and 73.5% (25/34) of PRKP strains showed a higher 7-day lethality in Galleria mellonella and a greater ability to resist complement-dependent killing than their corresponding PSKP, respectively.

CONCLUSION

Low dose with longer PMB treatment durations may be associated with the emergence of polymyxin resistance. The evolution of PRKP is predominantly mediated by an accumulation of mutations, including those in mgrB, yciC, and pmrB. Lastly, PRKP exhibited reduced growth and increased virulence compared with parental PSKP.

Factors Associated With Chlamydia and Gonorrhea Treatment Completion Among Sexual Health Clinic Patients, Baltimore City, Maryland; 2018 to 2019

BACKGROUND

Prompt and appropriate treatment of Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) is critical to prevent transmission and serious sequelae. The objectives were to determine the prevalence of CT/NG treatment completion and identify demographic, behavioral, and clinical factors associated with treatment completion at sexual health clinics in Baltimore City, Maryland.

METHODS

Electronic health record data from patients diagnosed with CT/NG during 2018-2019 were analyzed. Treatment completion was defined as documentation of Centers for Disease Control and Prevention-recommended treatment ≤30 days after testing. Regression was used to assess differences in treatment completion across groups; analyses were stratified by birth sex.

RESULTS

Most of the 2426 male (86%) and 754 (72%) female patients diagnosed with CT/NG completed treatment in ≤30 days; 74% of male and 36% of female patients were treated same-day. Among 890 male patients not treated same-day, treatment completion was associated with other same-day antimicrobial treatments (adjusted prevalence ratio, 0.76 [95% confidence interval, 0.61-0.94]), longer test processing times (≥10 days; 0.78 [0.65-0.95]) infection at multiple anatomic sites (1.49 [1.25-1.76]), and patients with previous clinic visits (1.16 [1.03-1.31]). Among 483 female patients not treated same-day, treatment completion was associated with diagnosis year (2019 vs. 2018; 1.23 [1.05-1.43]) and residential addresses 2 to 5 miles (vs. <2 miles) from clinic (1.25 [1.02-1.53]). Demographic and behavioral characteristics were not associated with treatment completion.

CONCLUSIONS

Substantial proportions of male and female sexual health clinic patients did not complete treatment. Our findings underscore the need for implementation of highly sensitive and specific point-of-care (POC) CT/NG testing to improve treatment completion in this setting.

Prior Exposure to Azithromycin and Azithromycin Resistance Among Persons Diagnosed With Neisseria gonorrhoeae Infection at a Sexual Health Clinic: 2012-2019

BACKGROUND

There is conflicting evidence on whether prior azithromycin (AZM) exposure is associated with reduced susceptibility to AZM (AZMRS) among persons infected with Neisseria gonorrhoeae (NG).

METHODS

The study population included Public Health-Seattle and King County Sexual Health Clinic (SHC) patients with culture-positive NG infection at ≥1 anatomic site whose isolates were tested for AZM susceptibility in 2012-2019. We used multivariate logistic regression to examine the association of time since last AZM prescription from the SHC in ≤12 months with subsequent diagnosis with AZMRS NG (minimum inhibitory concentration [MIC], ≥2.0 µg/mL) and used linear regression to assess the association between the number of AZM prescriptions in ≤12 months and AZM MIC level, controlling for demographic, behavioral, and clinical characteristics.

RESULTS

A total of 2155 unique patients had 2828 incident NG infections, 156 (6%) of which were caused by AZMRS NG. AZMRS NG was strongly associated with receipt of AZM from the SHC in the prior 29 days (adjusted odds ratio, 6.76; 95% confidence interval [CI], 1.76 to 25.90) but not with receipt of AZM in the prior 30-365 days. Log AZM MIC level was not associated with the number of AZM prescriptions within ≤12 months (adjusted correlation, 0.0004; 95% CI, -.04 to .037) but was associated with number of prescriptions within <30 days (adjusted coefficient, 0.56; 95% CI, .13 to .98).

CONCLUSIONS

Recent individual-level AZM treatment is associated with subsequent AZMRS gonococcal infections. The long half-life and persistence of subtherapeutic levels of AZM may result in selection of resistant NG strains in persons with recent AZM use.

Neonatal ocular prophylaxis in the United States: is it still necessary?

INTRODUCTION

Much has changed since Credé reported that silver nitrate decreases the incidence of ophthalmia neonatorum. Prenatal screening and treatment of pregnant women for Neisseria gonorrhoeae became standard in the 1950s and for Chlamydia trachomatis in 1993. Neonatal gonococcal and chlamydial conjunctivitis are consequently uncommon today. Currently, only 0.5% erythromycin ophthalmic ointment is available in the United States (U.S.) for neonatal ocular prophylaxis, which is ineffective against C. trachomatis.

AREAS COVERED

This article addresses the altered epidemiology of ophthalmia neonatorum in the U.S. since prophylactic practices began, the lack of data supporting ophthalmic erythromycin for prevention of neonatal gonococcal and chlamydial conjunctivitis, and the impact of prenatal screening and treatment of pregnant women for N. gonorrhoeae and C. trachomatis on conjunctivitis incidence. The authors discuss why erythromycin ophthalmic ointment is likely ineffective against gonococcal ophthalmia, including the development of macrolide resistance. Physiologic limitations and pharmacokinetic properties are considered with respect to ophthalmic erythromycin for the prevention of gonococcal and chlamydial conjunctivitis.

EXPERT OPINION

Administration of erythromycin ophthalmic ointment for the prevention of neonatal conjunctivitis is not literature-supported. Prenatal screening and treatment of pregnant women is the most effective way to prevent ophthalmia neonatorum. National mandates for prophylaxis should be withdrawn.

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.

Should we still use azithromycin for gonorrhoea treatment?

This review presents the evidence for azithromycin in the treatment of gonorrhoea, both as monotherapy and as a component of dual therapy. Uncertainties are explored regarding the efficacy of a dual treatment strategy, combining ceftriaxone and azithromycin, in the context of resistance trends and extra-genital infections. The association between microbiological testing and clinical outcome for the individual patient, and the effect of azithromycin use on other sexually transmissible infections, are considered. Finally, in the absence of imminent new antimicrobials, optimising the dose of azithromycin while maintaining tolerability is discussed.

Gentamicin as an alternative to ceftriaxone in the treatment of gonorrhoea: the G-TOG non-inferiority RCT

BACKGROUND

Gonorrhoea is a common sexually transmitted infection that can cause pain and discomfort, affect fertility in women and lead to epididymo-orchitis in men. Current treatment is with ceftriaxone, but there is increasing evidence of antimicrobial resistance reducing its effectiveness. Gentamicin is a potential alternative treatment requiring further evaluation.

OBJECTIVES

To assess the clinical effectiveness and cost-effectiveness of gentamicin as an alternative treatment to ceftriaxone in the treatment of gonorrhoea.

DESIGN

A multicentre, parallel-group, blinded, non-inferiority randomised controlled trial.

SETTING

Fourteen sexual health clinics in England.

PARTICIPANTS

Adults aged 16-70 years with a diagnosis of uncomplicated, untreated genital, pharyngeal or rectal gonorrhoea based on a positive Gram-stained smear on microscopy or a positive nucleic acid amplification test (NAAT).

RANDOMISATION AND BLINDING

Participants were randomised using a secure web-based system, stratified by clinic. Participants, investigators and research staff assessing participants were blinded to treatment allocation.

INTERVENTIONS

Allocation was to either 240 mg of gentamicin (intervention) or 500 mg of ceftriaxone (standard treatment), both administered as a single intramuscular injection. All participants also received 1 g of oral azithromycin.

MAIN OUTCOME MEASURE

The primary outcome measure was clearance of Neisseria gonorrhoeae at all infected sites, confirmed by a negative Aptima Combo 2® (Hologic Inc., Marlborough, MA, USA) NAAT, at 2 weeks post treatment.

RESULTS

We randomised 720 participants, of whom 81% were men. There were 358 participants in the gentamicin group and 362 in the ceftriaxone group; 292 (82%) and 306 (85%) participants, respectively, were included in the primary analysis. Non-inferiority of gentamicin to ceftriaxone could not be demonstrated [adjusted risk difference for microbiological clearance -6.4%, 95% confidence interval (CI) -10.4% to -2.4%]. Clearance of genital infection was similar in the two groups, at 94% in the gentamicin group and 98% in the ceftriaxone group, but clearance of pharyngeal infection and rectal infection was lower in the gentamicin group (80% vs. 96% and 90% vs. 98%, respectively). Reported pain at the injection site was higher for gentamicin than for ceftriaxone. The side-effect profiles were comparable between the groups. Only one serious adverse event was reported and this was deemed not to be related to the trial medication. The economic analysis found that treatment with gentamicin is not cost neutral compared with standard care, with average patient treatment costs higher for those allocated to gentamicin (£13.90, 95% CI £2.47 to £37.34) than to ceftriaxone (£6.72, 95% CI £1.36 to £17.84).

LIMITATIONS

Loss to follow-up was 17% but was similar in both treatment arms. Twelve per cent of participants had a negative NAAT for gonorrhoea at their baseline visit but this was balanced between treatment groups and unlikely to have biased the trial results.

CONCLUSIONS

The trial was unable to demonstrate non-inferiority of gentamicin compared with ceftriaxone in the clearance of gonorrhoea at all infected sites. Clearance at pharyngeal and rectal sites was lower for participants allocated to gentamicin than for those allocated to ceftriaxone, but was similar for genital sites in both groups. Gentamicin was associated with more severe injection site pain. However, both gentamicin and ceftriaxone appeared to be well tolerated.

FUTURE WORK

Exploration of the genetic determinants of antibiotic resistance in N. gonorrhoeae will help to identify accurate markers of decreased susceptibility. Greater understanding of the immune response to infection can assist gonococcal vaccine development.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN51783227.

FUNDING

This project was funded by the National Institute for Health Research Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 23, No. 20. See the NIHR Journals Library website for further project information.

Decreased Azithromycin Susceptibility of Neisseria gonorrhoeae Isolates in Patients Recently Treated with Azithromycin

Background

Increasing azithromycin usage and resistance in Neisseria gonorrhoeae threatens current dual treatment. Because antimicrobial exposure influences resistance, we analyzed the association between azithromycin exposure and decreased susceptibility of N. gonorrhoeae.

Methods

We included N. gonorrhoeae isolates of patients who visited the Amsterdam STI Clinic between 1999 and 2013 (t0), with another clinic visit in the previous 60 days (t-1). Exposure was defined as the prescription of azithromycin at t-1. Using multivariable linear regression, we assessed the association between exposure and azithromycin minimum inhibitory concentration (MIC). Whole genome sequencing (WGS) was performed to produce a phylogeny and identify multilocus sequence types (MLST), N. gonorrhoeae multiantigen sequence types (NG-MAST), and molecular markers of azithromycin resistance.

Results

We included 323 isolates; 212 were unexposed to azithromycin, 14 were exposed ≤30 days, and 97 were exposed between 31 and 60 days before isolation. Mean azithromycin MIC was 0.28 mg/L (range, <0.016-24 mg/L). Linear regression adjusted for age, ethnicity, infection site, and calendar year showed a significant association between azithromycin exposure ≤30 days and MIC (β, 1.00; 95% confidence interval, 0.44-1.56; P = .002). WGS was performed on 31 isolates: 14 unexposed, 14 exposed to azithromycin ≤30 days before isolation, and 3 t-1 isolates. Exposure to azithromycin was significantly associated with A39T or G45D mtrR mutations (P = .046) but not with MLST or NG-MAST types.

Conclusions

The results suggest that frequent azithromycin use in populations at high risk of contracting N. gonorrhoeae induces an increase in MIC and may result in resistance.

Antimicrobial Drug Prescription and Neisseria gonorrhoeae Susceptibility, United States, 2005-2013

We investigated whether outpatient antimicrobial drug prescribing is associated with Neisseria gonorrhoeae antimicrobial drug susceptibility in the United States. Using susceptibility data from the Gonococcal Isolate Surveillance Project during 2005–2013 and QuintilesIMS data on outpatient cephalosporin, macrolide, and fluoroquinolone prescribing, we constructed multivariable linear mixed models for each antimicrobial agent with 1-year lagged annual prescribing per 1,000 persons as the exposure and geometric mean MIC as the outcome of interest. Multivariable models did not demonstrate associations between antimicrobial drug prescribing and N. gonorrhoeae susceptibility for any of the studied antimicrobial drugs during 2005–2013. Elucidation of epidemiologic factors contributing to resistance, including further investigation of the potential role of antimicrobial drug use, is needed.

Is previous azithromycin treatment associated with azithromycin resistance in Neisseria gonorrhoeae? A cross-sectional study using national surveillance data in England

OBJECTIVES

It has been suggested that treatment of STIs with azithromycin may facilitate development of azithromycin resistance in Neisseria gonorrhoeae (NG) by exposing the organism to suboptimal doses. We investigated whether treatment history for non-rectal Chlamydia trachomatis (CT), non-gonococcal urethritis (NGU) or NG (proxies for azithromycin exposure) in sexual health (GUM) services was associated with susceptibility of NG to azithromycin.

METHODS

Azithromycin susceptibility data from the Gonococcal Resistance to Antimicrobials Surveillance Programme (GRASP 2013-2015, n=4606) and additional high-level azithromycin-resistant isolates (HL-AziR) identified by the Public Health England reference laboratory (2013-2016, n=54) were matched to electronic patient records in the national GUMCAD STI surveillance dataset (2012-2016). Descriptive and regression analyses were conducted to examine associations between history of previous CT/NGU/NG and subsequent susceptibility of NG to azithromycin.

RESULTS

Modal azithromycin minimum inhibitory concentration (MIC) was 0.25 mg/L (one dilution below the resistance breakpoint) in those with and without history of previous CT/NGU/NG (previous 1 month/6 months). There were no differences in MIC distribution by history of CT/NGU (P=0.98) or NG (P=0.85) in the previous 1 month/6 months or in the odds of having an elevated azithromycin MIC (>0.25 mg/L) (Adjusted OR for CT/NGU 0.97 (95% CI 0.76 to 1.25); adjusted OR for NG 0.82 (95% CI: 0.65 to 1.04)) compared with those with no CT/NGU/NG in the previous 6 months. Among patients with HL-AziR NG, 3 (4%) were treated for CT/NGU and 2 (3%) for NG in the previous 6 months, compared with 6% and 8%, respectively for all GRASP patients.

CONCLUSIONS

We found no evidence of an association between previous treatment for CT/NGU or NG in GUM services and subsequent presentation with an azithromycin-resistant strain. As many CT diagnoses occur in non-GUM settings, further research is needed to determine whether azithromycin-resistant NG is associated with azithromycin exposure in other settings and for other conditions.

Management of Gonorrhea in Adolescents and Adults in the United States

Gonorrhea is the second most commonly reported notifiable disease in the United States and is associated with serious health sequelae, including pelvic inflammatory disease, infertility, and ectopic pregnancy. Treatment for gonorrhea has been complicated by antimicrobial resistance. Neisseria gonorrhoeae has developed resistance to each of the antimicrobials that were previously recommended as first-line treatment regimens, and current treatment options are severely limited. This article summarizes the key questions and data that were discussed at the Sexually Transmitted Diseases (STD) Treatment Guidelines Expert Consultation meeting in April 2013, and the rationale for the 2015 Centers for Disease Control and Prevention STD treatment guidelines for gonococcal infections in adolescents and adults. Key issues addressed include whether to change the dosage of ceftriaxone and azithromycin used in the recommended dual treatment regimen, whether to continue to list dual treatment with cefixime and azithromycin as an alternative treatment regimen, and management of gonococcal infections in persons with severe cephalosporin allergy or suspected treatment failure.

Antimicrobial Resistance Expressed by Neisseria gonorrhoeae: A Major Global Public Health Problem in the 21st Century

Neisseria gonorrhoeae is a strictly human pathogen that is typically transmitted by sexual contact. The associated disease gonorrhea has plagued humankind for thousands of years, with a current estimated incidence of 78 million cases per year. Advances in antimicrobial discovery in the 1920s and 1930s leading to the discovery of sulfonamides and penicillin begun the era of effective antimicrobial treatment of gonorrhea. Unfortunately, the gonococcus developed decreased susceptibility or even resistance to these initially employed antibiotics, a trend that continued over subsequent decades with each new antibiotic that was brought into clinical practice. As this pattern of resistance has continued into the 21st century, there is now reason for great concern, especially in an era when few new antibiotics have prospects for use as treatment of gonorrhea. Here, we review the history of gonorrhea treatment regimens and gonococcal resistance to antibiotics, the mechanisms of resistance, resistance monitoring schemes that exist in different international settings, global responses to the challenge of resistance, and prospects for future treatment regimens in the 21st century.

Antimicrobial resistance in Neisseria gonorrhoeae in the 21st century: past, evolution, and future

Neisseria gonorrhoeae is evolving into a superbug with resistance to previously and currently recommended antimicrobials for treatment of gonorrhea, which is a major public health concern globally. Given the global nature of gonorrhea, the high rate of usage of antimicrobials, suboptimal control and monitoring of antimicrobial resistance (AMR) and treatment failures, slow update of treatment guidelines in most geographical settings, and the extraordinary capacity of the gonococci to develop and retain AMR, it is likely that the global problem of gonococcal AMR will worsen in the foreseeable future and that the severe complications of gonorrhea will emerge as a silent epidemic. By understanding the evolution, emergence, and spread of AMR in N. gonorrhoeae, including its molecular and phenotypic mechanisms, resistance to antimicrobials used clinically can be anticipated, future methods for genetic testing for AMR might permit region-specific and tailor-made antimicrobial therapy, and the design of novel antimicrobials to circumvent the resistance problems can be undertaken more rationally. This review focuses on the history and evolution of gonorrhea treatment regimens and emerging resistance to them, on genetic and phenotypic determinants of gonococcal resistance to previously and currently recommended antimicrobials, including biological costs or benefits; and on crucial actions and future advances necessary to detect and treat resistant gonococcal strains and, ultimately, retain gonorrhea as a treatable infection.

Analysis of Neisseria gonorrhoeae azithromycin susceptibility in the United States by the Gonococcal Isolate Surveillance Project, 2005 to 2013

Azithromycin, administered with ceftriaxone, is recommended by the CDC for the treatment of gonorrhea. Many experts have expressed concern about the ease with which Neisseria gonorrhoeae can acquire macrolide resistance. We sought to describe gonococcal azithromycin susceptibility in the United States and to determine whether azithromycin susceptibility has changed over time. We analyzed data from 2005 to 2013 from the Gonococcal Isolate Surveillance Project, a CDC-supported sentinel surveillance network that monitors gonococcal antimicrobial susceptibility. A total of 44,144 N. gonorrhoeae isolates were tested for azithromycin susceptibility by agar dilution methods. The overall azithromycin MIC50 was 0.25 μg/ml, and the MIC90 was 0.5 μg/ml. There were no overall temporal trends in geometric means. Isolates from men who had sex with men had significantly higher geometric mean MICs than isolates from men who had sex exclusively with women. The overall prevalence of reduced azithromycin susceptibility (MIC, ≥2 μg/ml) was 0.4% and varied by year from 0.3% (2006 and 2009) to 0.6% (2013). We did not find a clear temporal trend in gonococcal azithromycin MICs in the United States, and the prevalence of reduced azithromycin susceptibility remains low. These findings support the continued use of azithromycin in a combination therapy regimen for gonorrhea.

High prevalence of ciprofloxacin-resistant gonorrhea among female sex workers in Kampala, Uganda (2008-2009)

BACKGROUND

Recent antimicrobial resistance data for Neisseria gonorrhoeae are lacking in Uganda, where, until 2010, ciprofloxacin was the nationally recommended first-line treatment of presumptive gonorrhea. This study assessed the antimicrobial susceptibility patterns of N. gonorrhoeae isolates cultured from female sex workers (FSWs) in Kampala.

METHODS

Gonococci were isolated from endocervical specimens collected from women enrolled in a FSW cohort for 18 months (2008-2009). Minimum inhibitory concentrations for 7 antibiotics (ciprofloxacin, cefixime, ceftriaxone, azithromycin, spectinomycin, penicillin, and tetracycline) were determined for 148 isolates using Etest strips. The European Committee on Antimicrobial Susceptibility Testing version 1.3 clinical breakpoints were used to assign susceptibility categories. The 2008 World Health Organization N. gonorrhoeae panel was used for quality assurance purposes.

RESULTS

For ciprofloxacin, 123 (83.1%) gonococcal isolates were resistant, 2 (1.4%) had intermediate susceptibility, and 23 (15.6%) were fully susceptible. All isolates were susceptible to ceftriaxone and spectinomycin, whereas 1 isolate (0.7%) was resistant to cefixime. For azithromycin, 124 isolates (83.8%) were susceptible, 20 (13.5%) had decreased susceptibility, and 4 (2.7%) were resistant. Most isolates were resistant to penicillin (101; 68.2%) and tetracycline (144; 97.3%). The minimum inhibitory concentration ranges for each antibiotic were as follows: ciprofloxacin (0.002-32 mg/L), ceftriaxone (≤0.002-0.064 mg/L), cefixime (≤0.016-0.38 mg/L), spectinomycin (2-24 mg/L), azithromycin (0.023-1 mg/L), penicillin (0.094-32 mg/L), and tetracycline (0.019-256 mg/L).

CONCLUSIONS

The high prevalence of ciprofloxacin-resistant gonorrhea observed in Kampala-based FSW emphasizes the need for sustainable gonococcal antimicrobial resistance surveillance programs in Uganda and, in general, Africa.

Global resistance of Neisseria gonorrhoeae: when theory becomes reality

PURPOSE OF REVIEW

Neisseria gonorrhoeae has demonstrated a remarkable genetic capacity to acquire antimicrobial resistance (AMR) determinants. This review focuses on the recent developments in respect of third generation extended spectrum cephalosporin (ESC)-resistant gonorrhoea and the search for future treatment options.

RECENT FINDINGS

The estimated incidence of new gonorrhoea cases is increasing, and the antimicrobial resistance profile of N. gonorrhoeae is worsening. The most significant recent finding has been the emergence of extensively drug-resistant (XDR) N. gonorrhoeae characterized by very high ceftriaxone minimum inhibitory concentrations. A national switch from cefixime to high-dose ceftriaxone as first-line antigonococcal therapy in England and Wales, as well as parts of Japan, has been accompanied by a reduction in the prevalence of oral ESC-resistant gonococci. Azithromycin given in combination with either gentamicin or gemifloxacin has been shown to be an effective alternative antigonococcal therapy. Both ertapenem and solithromycin have good in-vitro activity against ESC-resistant N. gonorrhoeae strains.

SUMMARY

Current strategies to control gonococcal AMR should focus on the use of higher doses of ceftriaxone given as part of dual therapy and further evaluation of alternative drug combinations. The emergence of XDR gonorrhoea argues for enhanced efforts to develop novel antimicrobial agents and a gonococcal vaccine.

2012 European guideline on the diagnosis and treatment of gonorrhoea in adults

Gonorrhoea is a major public health concern globally. Of particularly grave concern is that resistance to the extended-spectrum cephalosporins has emerged during the most recent years. This guideline provides recommendations regarding the diagnosis and treatment of gonorrhoea in Europe. Compared to the outdated 2009 European gonorrhoea guideline, this 2012 European gonorrhoea guideline provides up-to-date guidance on, broader indications for testing and treatment of gonorrhoea;the introduction of dual antimicrobial therapy (ceftriaxone 500 mg and azithromycin 2 g) for uncomplicated gonorrhoea when the antimicrobial sensitivity is unknown; recommendation of test of cure in all gonorrhoea cases to ensure eradication of infection and identify emerging resistance; and recommendations to identify, verify and report failures with recommended treatment regimens. Optimisations of the testing, diagnostics, antimicrobial treatment and follow-up of gonorrhoea patients are crucial in controlling the emergent spread of cephalosporin-resistant and multidrug-resistant gonorrhoea.

Emergence of increased azithromycin resistance during unsuccessful treatment of Neisseria gonorrhoeae infection with azithromycin (Portland, OR, 2011)

We describe the emergence of an azithromycin-resistant Neisseria gonorrhoeae variant in a man from Portland, Oregon, during sole treatment with 2 g azithromycin. This report highlights the ease with which gonococcal macrolide resistance can emerge, the threat of multidrug resistant N. gonorrhoeae, and the need for adherence to Centers for Disease Control and Prevention treatment guidelines.

Emergence of fluoroquinolone resistance in Neisseria gonorrhoeae isolates from four clinics in three regions of Kenya

We have recently reported high levels of fluoroquinolone resistance in a single region of Kenya. In this article, we report high prevalence of fluoroquinolone resistance (53.2%) in Neisseria gonorrhoeae isolates from 4 clinics in 3 additional regions of Kenya. These findings highlight the need to change first-line treatment in these settings and the need to evaluate empirical management guidelines for treatment of gonococcal infection in Kenya.

UK national guideline for the management of gonorrhoea in adults, 2011

The British Association for Sexual Health and HIV (BASHH) UK gonorrhoea guideline has been updated in 2011. It offers advice on diagnosis, treatment and health promotion for anogenital and pharyngeal gonorrhoea. Nucleic acid amplification tests (NAATs) are now being used more for diagnosis and are increasing detection rates in the pharynx and rectum. First line treatment using ceftriaxone with azithromycin is now advised, along with routine test of cure (TOC). The aim is to slow the spread of resistant gonorrhoea now that fewer antibiotics remain effective. A patient information leaflet has been developed.

Cephalosporin Resistance in Neisseria gonorrhoeae

Gonorrhea, a disease of public health importance, not only leads to high incidence of acute infections and complications but also plays a major role in facilitating human immunodeficiency virus (HIV) acquisition and transmission. One of the major public health needs for gonorrhea control is appropriate, effective treatment. However, treatment options for gonorrhea are diminishing as Neisseria gonorrhoeae have developed resistance to several antimicrobial drugs such as sulfonamides, penicillin, tetracyclines and quinolones. Antimicrobial resistance (AMR) surveillance of N. gonorrhoeae helps establish and maintain the efficacy of standard treatment regimens. AMR surveillance should be continuous to reveal the emergence of new resistant strains, monitor the changing patterns of resistance, and be able to update treatment recommendations so as to assist in disease control. Current treatment guidelines recommend the use of single dose injectable or oral cephalosporins. The emergence and spread of cephalosporin resistant and multi drug resistant N. gonorrhoeae strains, represents a worrying trend that requires monitoring and investigation. Routine clinical laboratories need to be vigilant for the detection of such strains such that strategies for control and prevention could be reviewed and revised from time to time. It will be important to elucidate the genetic mechanisms responsible for decreased susceptibility and future resistance. There is also an urgent need for research of safe, alternative anti-gonococcal compounds that can be administered orally and have effective potency, allowing high therapeutic efficacy (greater than 95.0% cure rate).

Emergence of high-level azithromycin resistance in Neisseria gonorrhoeae in England and Wales

OBJECTIVES

This study aimed to investigate the origin of high-level azithromycin resistance that emerged in isolates of Neisseria gonorrhoeae in England and Wales in 2007, and to establish methods for identifying high-level azithromycin resistance.

METHODS

The Gonococcal Resistance to Antimicrobials Surveillance Programme (GRASP) data from 2001-07 were examined for emerging trends in azithromycin susceptibility. Further to the identification of six high-level azithromycin-resistant isolates in GRASP 2007, an additional 102 isolates were selected on the basis of azithromycin susceptibility and geographic origin from the GRASP 2006 and 2007 collections. Susceptibility testing by Etest and disc diffusion was performed on all 108 isolates and 75 of these were typed by N. gonorrhoeae multiantigen sequence typing.

RESULTS

A slight drift towards higher MICs of azithromycin was observed in the gonococcal population since 2001. Of greater concern was the first example of a shift to high-level resistance observed in six isolates in 2007. All six isolates were sequence type 649, which was not observed in any of the lower-level azithromycin-resistant isolates from 2007 or in any isolates tested from the same geographical locations. Contact tracing data for one patient suggested a link with Scotland. Disc diffusion testing of all 108 isolates showed that azithromycin, but not erythromycin, discs can differentiate between low-level and high-level resistance.

CONCLUSIONS

High-level azithromycin resistance has emerged in England and Wales. Contact tracing and typing data suggest this may have originated from Scotland. Surveillance of azithromycin resistance will be key in controlling its further dissemination.

Update on the management of gonorrhea in adults in the United States

Gonorrhea, the second most commonly reported notifiable disease, is an important cause of cervicitis, urethritis, and pelvic inflammatory disease. The selection of appropriate therapy for gonorrhea (i.e., safe, highly effective, single dose, and affordable) is complicated by the ability of Neisseria gonorrhoeae to develop resistance to antimicrobial therapies. This article reviews the key questions and data that informed the 2006 gonorrhea treatment recommendations of the Centers for Disease Control and Prevention. Key areas addressed include the criteria used to select effective treatment for gonorrhea, the level of antimicrobial resistance at which changing treatment regimens is recommended, the epidemiology of resistance, and the use of quinolones, cephalosporins, and other classes of antimicrobials for the treatment of uncomplicated gonorrhea.

Pharyngeal Gonorrhea in Female Sex Workers: Response to a Single 2-g Dose of Azithromycin

OBJECTIVES

A sharp increase in the incidence of gonorrhea has been observed in Tel Aviv, Israel, since 1999. Almost one half of interviewed patients admitted contracting the infection from a sex worker. In two thirds of the cases, oral sex (fellatio) was the most probable route of acquiring the disease. In the current study, we assessed the prevalence of pharyngeal gonorrhea among sex workers in Tel Aviv and evaluated the efficacy of a single 2-g dose of azithromycin in eradicating the infection.

METHODS

Throat specimens were obtained for gonococcal culture from 301 female sex workers practicing in brothels. A questionnaire covering demographic and sexual behavior information was administered to all participants, and a single 2-g dose was administered orally under supervision. Women with positive cultures were reexamined a week later for eradication of Neisseria gonorrhoeae.

RESULTS

N gonorrhoeae was isolated from 27 women (9%). The median age of women with pharyngeal gonorrhea was 23 years (range, 18-32 years); 85% were born in former Soviet Union (mostly Russia, Ukraine, Moldavia). Regular condom use in vaginal sex was reported by 88% of the participants, whereas only 60% reported always using condoms in oral sex. All isolates were susceptible to azithromycin (MIC < or = 0.5 microg/ml). Gonococci were eradicated in 20/21 individuals (95%).

CONCLUSION

A high carriage rate of gonococci in the throat and a low rate of condom use in oral sex were documented among sex workers in Tel Aviv. A single 2 g dose of azithromycin was very effective in eradicating gonococci from the throat.

Antimicrobial resistance of Neisseria gonorrhoeae isolates from the Stuttgart and Heidelberg areas of southern Germany

The aim of the present study was to determine prospectively the antimicrobial susceptibility of Neisseria gonorrhoeae strains collected in southern Germany (Heidelberg and Stuttgart areas). Sixty-five N. gonorrhoeae strains, isolated between July 2004 and June 2005 from patients with uncomplicated gonorrhoea, were tested. Minimum inhibitory concentrations of penicillin, tetracycline, ciprofloxacin, azithromycin, spectinomycin, ceftriaxone, and cefixime were determined by the E test. All isolates were fully susceptible to ceftriaxone, cefixime, and spectinomycin. However, 21.5% (14/65), 29.2% (19/65), and 47.7% (31/65) of isolates were resistant to penicillin (>2.0 mg/l), tetracycline (>2.0 mg/l), and ciprofloxacin (>1.0 mg/l), respectively. Critical MICs of azithromycin (>1.0 mg/l, as defined by the Neisseria Reference Laboratory at the Centers for Disease Control) were found for five (7.7%) N. gonorrhoeae isolates. These data indicate a high prevalence of N. gonorrhoeae strains resistant to the antimicrobial agents currently used to treat gonococcal infections in the Heidelberg and Stuttgart areas. Even though the findings may not be representative of the general population in Germany, they nevertheless illustrate the need to establish an antimicrobial resistance surveillance system in order to control gonorrhoea effectively.

Activity of gemifloxacin tested against Neisseria gonorrhoeae isolates including antimicrobial-resistant phenotypes

The antigonococcal potency of gemifloxacin and 5 reference comparator antimicrobials was determined for a selected collection of gonococcal isolates. The 250 Neisseria gonorrhoeae strains were inclusive of (1) 50 historic strains from Japan with elevated fluoroquinolone minimal inhibitory concentration values (QRNG) and (2) 200 contemporary strains from clinical specimens in 2004 (176 from 6 sentinel sites in the United States and 24 bacteremic isolates from the SENTRY Antimicrobial Surveillance Program). The rank order of potency of the tested antimicrobials for the entire collection was: ceftriaxone (MIC(90) = 0.06 microg/mL) > gemifloxacin (1 microg/mL) > tetracycline (2 microg/mL) > ciprofloxacin = levofloxacin = penicillin (4 microg/mL). The activity of gemifloxacin was not affected by penicillinase production; however, its activity was decreased for penicillin-resistant strains. Cross-resistance between gemifloxacin and the older fluoroquinolones was present, and the gemifloxacin MIC90 value was higher for the ciprofloxacin-resistant strains compared with the ciprofloxacin-susceptible strains (2 versus 0.016 mug/mL, respectively). More than 20.0% of the recent clinical strains were resistant to penicillin, tetracycline, and ciprofloxacin with >30.0% of gonococci resistant to ciprofloxacin in Washington State and Hawaii. The historic QRNG strains from the Far East were predominantly of intermediate susceptibility (88.0%) to ciprofloxacin, with a gemifloxacin MIC90 value of only 0.25 microg/mL. The bacteremic gonococcal strains were exquisitely susceptible to the 3 quinolones tested (ciprofloxacin, levofloxacin, and gemifloxacin, MIC90 at < or = 0.03 microg/mL) and ceftriaxone (MIC90 = 0.06 microg/mL). In summary, the potency of gemifloxacin was competitive and positioned between that of ceftriaxone and older quinolones or penicillin or tetracycline, irrespective of the gonococcal resistance phenotype. Gemifloxacin should be considered for further development as a therapeutic option to treat uncomplicated infections due to emerging strains resistant to penicillins, tetracycline, and some older fluoroquinolones.

The Emergence of Neisseria gonorrhoeae With Decreased Susceptibility to Azithromycin in Kansas City, Missouri, 1999 to 2000

BACKGROUND AND OBJECTIVES

We describe the first cluster of persons with Neisseria gonorrhoeae with decreased susceptibility to azithromycin (AziDS; minimum inhibitory concentration >/=1.0 microg/mL) in the United States. GOAL The goal of this study was to identify risk factors for AziDS N. gonorrhoeae and to describe isolate microbiology.

STUDY DESIGN

Persons with AziDS N. gonorrhoeae (cases) were identified in Kansas City, Missouri, through the Gonococcal Isolate Surveillance Project (GISP) in 1999 and expanded surveillance, January 2000 to June 2001. A case-control study using 1999 GISP participants was conducted; control subjects had azithromycin-susceptible N. gonorrhoeae.

RESULTS

Thirty-three persons with AziDS N. gonorrhoeae were identified. Case patients were older than control patients (median age, 33 years vs. 23 years; P <0.001). Fifty percent of cases and 13% of control subjects had a history of sex with a female commercial sex worker (odds ratio, 7.0; 95% confidence interval, 1.3-36.0); 50% of cases and 4% of control subjects met sex partners on street A (P <0.01). AziDS N. gonorrhoeae isolates were phenotypically and genotypically similar and contained an mtrR gene mutation.

CONCLUSIONS

With few treatment options remaining, surveillance for antimicrobial-resistant N. gonorrhoeae is increasingly important, especially among persons at high risk.

Multidrug-resistant Neisseria gonorrhoeae with decreased susceptibility to cefixime-Hawaii, 2001

We report 4 urogenital Neisseria gonorrhoeae isolates recovered from 3 patients that demonstrated resistance to penicillin, tetracycline, and ciprofloxacin and reduced susceptibility to cefixime. This report of the first 3 patients in the United States identified with this multidrug-resistant strain may portend an emerging problem for clinicians and public health officials.

A cost-effectiveness evaluation of testing and treatment of Chlamydia trachomatis infection among asymptomatic women infected with Neisseria gonorrhoeae

BACKGROUND

Because patients infected with Neisseria gonorrhoeae are frequently coinfected with Chlamydia trachomatis, routine dual treatment of patients with N gonorrhoeae infection is frequently practiced and has long been recommended.

GOAL

The goal of this study was to examine the cost-effectiveness of routine dual treatment of women with infection, with or without separate testing for C trachomatis, compared with an alternative of testing for both infections and restricting treatment for C trachomatis to women testing positive for C trachomatis.

STUDY DESIGN

A decision analysis compared the cost-effectiveness of these options using cases of pelvic inflammatory disease prevented as the outcome. Parameter values were taken from the literature.

RESULTS

Routine dual treatment is not an effective or cost-effective replacement for testing for C trachomatis, but it can increase the number of cases of C trachomatis treated when combined with testing. Dual treatment results in more overtreatment of infection C trachomatis than treatment based on test results.

CONCLUSIONS

Testing for both infections is more cost-effective than routine presumptive treatment for C trachomatis. Providing both presumptive treatment and testing for C trachomatis can also be cost-effective in some settings.

How predictive is PK/PD for antibacterial agents?

The pharmacodynamic (PD) parameters most often used in studies of antibiotic effect include the following relationships between the antibiotic concentration curve in serum as a surrogate marker for the antibiotic concentration at the infection site, the peak/minimal inhibitory concentration (MIC) ratio, the area under the curve (AUC)/MIC ratio and the duration of time the concentration exceeds the MIC (T(>MIC)). The MIC plays an important role also as a PD marker, and its precision in this respect is discussed. The predictive role of T(>MIC) is important for drugs showing minimal concentration dependent effect such as the beta-lactam antibiotics, the macrolides and others. The time can be calculated as the chronological time measured or as the (cumulative) per cent of the dosing interval covered by the dose. Several clinical studies have confirmed this relationship. It can be deduced from experimental as well as clinical studies that there is a minimal effective time (MET), which needs to be covered by the antibiotic concentration at the site of infection in order to achieve cure. Dosing according to this MET will result in the least antibiotic needed for the shortest duration. In several cases a single dose will suffice to cover the MET. If this is not possible the antibiotic should be dosed in a way, that each dose will surpass the MIC for at least 40-50% of the dosing interval. For antibiotics with a clear concentration-dependent bacterial killing effect the most important pharmacokinetic/pharmacodynamic (PK/PD) index is the peak/MIC ratio (or the AUC/MIC ratio). This is the case for aminoglycosides and fluoroquinolones, and for both classes a peak/MIC ratio of at least 10 within the first 24 h of treatment has been shown to result in around 90% bacteriological as well as clinical cure. One consequence of clinical dosing has been the once-a-day (OD) dosing for aminoglycosides, which is the standard mode of therapy in many countries. Clinical studies in the field of antibacterial PD are still relatively scarce, and much information is needed to enable relevant dosing strategies for all types of antibiotics against all common infections and micro-organisms.

Current concepts in the management of gonorrhoea

The incidence of gonorrhoea is again rising in developed countries and a high disease rate has been maintained in less developed regions for a number of years. The need not only for treatment of the individual but also for control of gonorrhoea at a community level has increased significantly following recognition of its role in the amplification of human immunodeficiency virus (HIV) transmission. A sustainable decrease in the incidence of gonorrhoea and other sexually transmitted diseases (STDs) requires an integrated approach combining improved prevention, better diagnosis and optimal treatment. Effective antibiotic treatment is an essential element of this approach. However, antibiotic treatment of gonorrhoea has been severely hampered by the development of antibiotic resistance in Neisseria gonorrhoeae, to the extent that many therapies are no longer effective. Those treatments that retain acceptable efficacy are often unaffordable where they are most needed. Penicillins and tetracyclines should no longer be used in gonococcal disease, there are limitations on the effectiveness of newer macrolides and spectinomycin and in many parts of the world quinolones have been withdrawn from schedules for the treatment of gonorrhoea. Of all the current agents used to treat all forms of gonococcal disease, only the third generation cephalosporins (most notably ceftriaxone) have retained their efficacy; however, decreased susceptibility to these antibiotics has also appeared. Continuing reliance on antibiotic treatment for controlling gonorrhoea in the absence of other necessary approaches will see a further deterioration in the situation. In these circumstances the possibility that gonorrhoea will be untreatable becomes more real.

Reduced susceptibility to azithromycin and high percentages of penicillin and tetracycline resistance in Neisseria gonorrhoeae isolates from Manaus, Brazil, 1998

BACKGROUND

The identification of Neisseria gonorrhoeae isolates resistant to antimicrobial agents currently recommended for the treatment of gonococcal infections continues to escalate globally. Thus, in some areas, resistance to fluoroquinolone drugs is commonplace; several reports document resistance to third-generation cephalosporins, and the sporadic isolation of spectinomycin-resistant isolates continues unabated. Gonococcal resistance to azithromycin, an antibiotic used for the primary treatment of gonococcal infections in some Latin American countries, also has been described. Because the prevalence of resistant isolates is insufficiently documented in many areas of Latin America, the efficacy of locally recommended therapies for gonococcal infections is often unknown.

GOAL

To determine the antimicrobial susceptibility and strain types of N gonorrhoeae isolates collected in Manaus, Brazil. These data will establish antimicrobial susceptibility baseline data for the region as a reference point for future surveillance.

STUDY DESIGN

Consecutive N gonorrhoeae isolates from urethral and endocervical specimens were collected and examined for identity, antimicrobial susceptibility, and strain type (plasmid content, tetM type, auxotype, and serovar).

RESULTS

Most of the isolates (65/81; 85.2%) were resistant to tetracycline, penicillin, or both, with the majority (n = 62) carrying plasmid-mediated resistance to tetracycline (tetracycline-resistant N gonorrhoeae [TRNG]). All of the TRNG contained the Dutch-type tetM plasmid, and 18 were A/S class NR/IA-02. Penicillinase-producing N gonorrhoeae comprised 8.2% (7/81) of the isolates. Of these seven isolates, four also were TRNG, and two carried chromosomal resistance to tetracycline. The isolates were susceptible to ciprofloxacin, spectinomycin, and ceftriaxone. However, 23 isolates were characterized by reduced susceptibility to azithromycin (MIC, 0.25-0.5 microg/ml), and one isolate had reduced susceptibility to ciprofloxacin (MIC, 0.25 microg/ml).

CONCLUSIONS

This study supports the continued use of third-generation cephalosporins, spectinomycin, and fluoroquinolone drugs for the primary treatment of gonococcal infections in Manaus. The occurrence of isolates with reduced susceptibility to azithromycin and ciprofloxacin underscores the importance of ongoing antimicrobial susceptibility monitoring to support decisions regarding appropriate drugs for the treatment of gonococcal infections.

Antimicrobial susceptibility of Neisseria gonorrhoeae isolates from three Caribbean countries: Trinidad, Guyana, and St. Vincent

BACKGROUND

The percentage of Neisseria gonorrhoeae isolates resistant to antimicrobial agents commonly used for treatment is unknown in many Caribbean countries.

GOAL

To determine the antimicrobial susceptibility of N gonorrhoeae isolates from Trinidad (144 isolates), Guyana (70 isolates), and St. Vincent (68 isolates) so baseline data can be established for further studies, and to assist in establishing effective treatment guidelines.

STUDY DESIGN

Consecutive urethral and endocervical specimens from several clinics were collected and identified as N gonorrhoeae. Isolates of N gonorrhoeae were tested for their susceptibility to penicillin, tetracycline, ceftriaxone, ciprofloxacin, spectinomycin, and azithromycin. The presumptive identification of penicillinase-producing N gonorrhoeae and/or tetracycline-resistant N gonorrhoeae isolates based on MIC was confirmed by plasmid and tetM content analysis.

RESULTS

High percentages of penicillin and/or tetracycline resistance were observed in N gonorrhoeae isolates from Guyana (92.9%), St. Vincent (44.1%), and Trinidad (42.4%). Isolates from all three countries were susceptible to ceftriaxone, ciprofloxacin, and spectinomycin. One penicillinase-producing N gonorrhoeae/tetracycline-resistant N gonorrhoeae from Guyana had an MIC of 0.5 microg/l to ciprofloxacin. This and nine other isolates from Guyana also were resistant to azithromycin (defined as MIC > or = 2.0 microg/ml) as well as penicillin and tetracycline. A reduced susceptibility to azithromycin was displayed by 16% of the isolates from St. Vincent and 72% of the isolates from Guyana (MIC, 0.25-1.0 microg/ml). Most penicillinase-producing N gonorrhoeae isolates carried Africa-type plasmids (61/90), with 28 of 90 having Toronto-type plasmids and a single isolate carrying an Asia-type plasmid. The tetM determinant in tetracycline-resistant N gonorrhoeae isolates was predominantly of the Dutch type (68/91).

CONCLUSIONS

The high prevalence of N gonorrhoeae isolates from 3 of 21 English- and Dutch-speaking Caricom countries in the Caribbean with either plasmid-mediated or chromosomal resistance to penicillin and tetracycline supports international observations that these drugs should not be used to treat gonococcal infections. The detection of isolates with reduced susceptibility to drugs such as azithromycin, which currently are recommended for treatment in the region, attest to the importance of the continued monitoring of gonococcal antimicrobial susceptibility for the maintenance of effective treatment guidelines.

Erythromycin-resistant Neisseria gonorrhoeae and oral commensal Neisseria spp. carry known rRNA methylase genes

Two Neisseria gonorrhoeae isolates from Seattle and two isolates from Uruguay were resistant to erythromycin (MIC, 4 to 16 microg/ml) and had reduced susceptibility to azithromycin (MIC, 1 to 4 microg/ml) due to the presence of the self-mobile rRNA methylase gene(s) ermF or ermB and ermF. The two Seattle isolates and one isolate from Uruguay were multiresistant, carrying either the 25.2-MDa tetM-containing plasmid (Seattle) or a beta-lactamase plasmid (Uruguay). Sixteen commensal Neisseria isolates (10 Neisseria perflava-N. sicca, 2 N. flava, and 4 N. mucosa) for which erythromycin MICs were 4 to 16 microg/ml were shown to carry one or more known rRNA methylase genes, including ermB, ermC, and/or ermF. Many of these isolates also were multiresistant and carried the tetM gene. This is the first time that a complete transposon or a complete conjugative transposon carrying an antibiotic resistance gene has been described for the genus Neisseria.

Failure of azithromycin therapy in gonorrhea and discorrelation with laboratory test parameters

BACKGROUND

Azithromycin is efficacious in the treatment of chlamydial genital tract infection but less so in gonorrhea. However, MICs of azithromycin for gonococci from previously reported azithromycin treatment failures were consistently below the 'susceptible' MIC level of 2 mg/L.

GOAL OF THIS STUDY

To examine gonococci not eliminated with 1 g azithromycin therapy to establish treatment outcome/MIC correlates in gonorrhea.

STUDY DESIGN

The MICs and phenotypes of gonococci isolated from five cases of treatment failure after 1 g azithromycin therapy were determined and compared with the MICs of a systematic sample of routine isolates.

RESULTS

Azithromycin MICs of gonococci from five cases of failed 1 g azithromycin treatment were 0.125 or 0.25 mg/L, well within the current 'susceptible' MIC range. None of the isolates were of the mtr phenotype. The MIC90 of a systematic sample of 219 gonococcal isolates was 0.25 mg/L.

CONCLUSION

The antibiotic MIC/treatment outcome correlates that are usually found in gonorrhea do not apply for azithromycin. Current MIC criteria do not accurately define susceptibility or resistance of gonococci to azithromycin and by themselves do not predict the likely outcome of therapy. Pharmacokinetic factors may decrease the predictive value of MIC data.