Neisseria gonorrhoeae with high-level resistance to azithromycin: case report of the first isolate identified in the United States

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

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

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.

Antimicrobial susceptibility/resistance and NG-MAST characterisation of Neisseria gonorrhoeae in Belarus, Eastern Europe, 2010-2013

Background

Gonorrhoea and widely spread antimicrobial resistance (AMR) in its etiological agent Neisseria gonorrhoeae are major public health concerns worldwide. Gonococcal AMR surveillance nationally and internationally, to identify emerging resistance and inform treatment guidelines, is imperative for public health purposes. In 2009, AMR surveillance was initiated in Belarus, Eastern Europe because no gonococcal AMR data had been available for at least two decades. Herein, the prevalence and trends of gonococcal AMR and molecular epidemiological characteristics of N. gonorrhoeae strains from 2010 to 2013 in Belarus, are described.

Methods

N. gonorrhoeae isolates (n=193) obtained in the Mogilev (n=142), Minsk (n=36) and Vitebsk (n=15) regions of Belarus in 2010 (n=72), 2011 (n=6), 2012 (n=75) and 2013 (n=40) were analyzed in regards to AMR using the Etest method and for molecular epidemiology with N. gonorrhoeae multi-antigen sequence typing (NG-MAST).

Results

During 2010–2013, the proportions of resistant N. gonorrhoeae isolates were as follows: tetracycline 36%, ciprofloxacin 28%, penicillin G 9%, azithromycin 5%, and cefixime 0.5%. Only one (0.5%) β-lactamase producing isolate was detected. No isolates resistant to ceftriaxone and spectinomycin were identified. Overall, the resistance levels to tetracycline, ciprofloxacin and penicillin G were relatively stable. Interestingly, the level of resistance to azithromycin declined from 12% in 2010 to 0% in 2013 (P < 0.05). In total, 70 NG-MAST STs were identified. The predominant STs were ST1993 (n=53), ST807 (n=13), ST285 (n=8) and ST9735 (n=8). Many novel STs (n=43, 61%), representing 41% of all isolates, were found.

Conclusions

During 2010–2013, the N. gonorrhoeae population in Belarus displayed high and relatively stable resistance levels to tetracycline, ciprofloxacin, and penicillin G, while the resistance to azithromycin declined. One isolate was resistant to cefixime, but no resistance to ceftriaxone or spectinomycin was found. The results of the present surveillance initiated in 2009 were also used to replace penicillin G with ceftriaxone (1 g single dose intramuscularly) as the first-line drug for empiric treatment of gonorrhoea in the national treatment guidelines in Belarus in late 2009. It is essential to further strengthen the surveillance of gonococcal AMR and ideally survey also treatment failures and molecular epidemiological genotypes in Belarus.

The second nationwide surveillance of the antimicrobial susceptibility of Neisseria gonorrhoeae from male urethritis in Japan, 2012-2013

Worldwide, the most important concern in the treatment of sexually transmitted infections is the increase in antimicrobial resistant Neisseria gonorrhoeae strains including resistance to cephalosporins, penicillins, fluoroquinolones or macrolides. To investigate the trends of antimicrobial susceptibility among N. gonorrhoeae strains isolated from male patients with urethritis, a Japanese surveillance committee conducted the second nationwide surveillance study. Urethral discharge was collected from male patients with urethritis at 26 medical facilities from March 2012 to January 2013. Of the 151 specimens, 103 N. gonorrhoeae strains were tested for susceptibility to 20 antimicrobial agents. None of the strains was resistant to ceftriaxone, but the minimum inhibitory concentration (MIC) 90% of ceftriaxone increased to 0.125 μg/ml, and 11 (10.7%) strains were considered less susceptible with an MIC of 0.125 μg/ml. There were 11 strains resistant to cefixime, and the MICs of these strains were 0.5 μg/ml. The distributions of the MICs of fluoroquinolones, such as ciprofloxacin, levofloxacin and tosufloxacin, were bimodal. Sitafloxacin, a fluoroquinolone, showed strong activity against all strains, including strains resistant to other three fluoroquinolones, such as ciprofloxacin, levofloxacin and tosufloxacin. The azithromycin MICs in 2 strains were 1 μg/ml.

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.

What's new in sexually transmitted infections in the HIV care setting: focus on syphilis and gonorrhea

Sexually transmitted infections are a resurgent problem in HIV disease. The number of new cases of syphilis among men who have sex with men has continued to increase, requiring renewed vigilance in screening, diagnosis, and treatment. Drug-resistant gonorrhea has prompted changes in treatment regimens and warrants continued monitoring. This article summarizes an IAS-USA continuing education webinar presented by Jeanne M. Marrazzo, MD, MPH, in January 2014.

High-level azithromycin-resistant Neisseria gonorrhoeae clinical isolate in France, March 2014

We report the first case in France of a high-level azithromycin-resistant Neisseria gonorrhoeae (minimum inhibitory concentration (MIC) = 96 mg/L) assigned to MLST7363 (NG-MAST ST6360), also resistant to ciprofloxacin and tetracycline but susceptible to ceftriaxone. The patient was a 51 year-old heterosexual man who returned following 1g azithromycin monotherapy. Mechanisms of azithromycin resistance were a C2599T mutation in the four copies of the rrl gene and a novel mutation in the promoter of the mtrR gene.

Persistence of Neisseria gonorrhoeae DNA following treatment for pharyngeal and rectal gonorrhea is influenced by antibiotic susceptibility and reinfection

BACKGROUND

To guide interpretation of gonorrhea tests of cure using nucleic acid amplification testing, this study examined the persistence of Neisseria gonorrhoeae DNA following treatment for pharyngeal and rectal gonorrhea.

METHODS

Men who had sex with men diagnosed with pharyngeal or rectal gonorrhea underwent swabbing from the pharynx or rectum 7 and 14 days following treatment. Repeat testing for N. gonorrhoeae was undertaken using real-time polymerase chain reaction (PCR) assays targeting the opa gene and porA pseudogene.

RESULTS

One hundred pharyngeal and 100 rectal gonorrhea infections in 190 men were included. For pharyngeal gonorrhea, positivity of N. gonorrhoeae DNA on both PCR assays was present at days 7 or 14 in 13% (95% confidence interval [CI], 6.4%-19.6%) and 8% (95% CI, 2.7%-13.3%), respectively. For rectal gonorrhea, DNA positivity was present in 6% (95% CI, 1.4%-10.7%) and 8% (95% CI, 2.7%-13.3%), respectively. Among 200 baseline pharyngeal and rectal isolates, there were 10 with ceftriaxone minimum inhibitory concentration (MIC) ≥0.06 mg/L and azithromycin MIC ≥0.5 mg/L, of which 3 (30%) had DNA detected at day 14; among the 190 isolates with lower ceftriaxone and azithromycin MICs, only 13 (7%) had persistent DNA (odds ratio, 5.8 [95% CI, 1.3-25.4]; P = .019). One man initially infected with N. gonorrhoeae multiantigen sequence type 2400 had type 4244 infection at day 14, indicating reinfection.

CONCLUSIONS

Pharyngeal and rectal gonorrhea DNA persisted in 8% of men 14 days after treatment. Persistence was associated with elevated ceftriaxone and azithromycin MICs. Persistence can also reflect reinfection.

Russian gonococcal antimicrobial susceptibility programme (RU-GASP)--resistance in Neisseria gonorrhoeae during 2009-2012 and NG-MAST genotypes in 2011 and 2012

Background

Antimicrobial resistance (AMR) in Neisseria gonorrhoeae is a major concern worldwide and gonococcal AMR surveillance globally is imperative for public health purposes. In Eastern Europe, gonococcal AMR surveillance is exceedingly rare. However, in 2004 the Russian gonococcal antimicrobial susceptibility programme (RU-GASP) was initiated. The aims of this study were to describe the prevalence and trends of gonococcal AMR from 2009 to 2012, and molecular epidemiological genotypes in 2011 and 2012 in Russia.

Methods

Gonococcal isolates from 12–46 surveillance sites distributed across Russia, obtained in 2009 (n = 1200), 2010 (n = 407), 2011 (n = 423), and 2012 (n = 106), were examined for antimicrobial susceptibility using agar dilution method. Gonococcal isolates from 2011 and 2012 were investigated with N. gonorrhoeae multi-antigen sequence typing (NG-MAST).

Results

During 2009–2012, the proportions of gonococcal isolates resistant to ciprofloxacin, penicillin G, azithromycin and spectinomycin ranged from 25.5% to 44.4%, 9.6% to 13.2%, 2.3% to 17.0% and 0.9% to 11.6%, respectively. Overall, the resistance level to penicillin G was stable, the resistance level to ciprofloxacin was decreasing, however, the level of resistance to azithromycin increased. All isolates were susceptible to ceftriaxone using the US CLSI breakpoints. However, using the European breakpoints 58 (2.7%) of the isolates were resistant to ceftriaxone. Interestingly, this proportion was decreasing, i.e. from 4.8% in 2009 to 0% in 2012.

Conclusions

In Russia, the diversified gonococcal population showed a high resistance to ciprofloxacin, penicillin G and azithromycin. In general, the MICs of ceftriaxone were relatively high, however, they were decreasing from 2009 to 2012. Ceftriaxone should be the first-line for empiric antimicrobial monotherapy of gonorrhoea in Russia. It is essential to further strengthen the surveillance of gonococcal AMR (ideally also gonorrhoea treatment failures) in Russia.

Azithromycin resistance is coevolving with reduced susceptibility to cephalosporins in Neisseria gonorrhoeae in Ontario, Canada

Azithromycin (AZM) is routinely recommended as a component of dual therapy for gonorrhea in combination with third-generation cephalosporins (3GC). In this study, we examined the prevalence of AZM-resistant (AZM(r)) Neisseria gonorrhoeae from July 2010 to February 2013, assessed the rate of concurrent cephalosporin resistance under the current treatment recommendations, and analyzed the clonal distribution of AZM(r) isolates in Ontario, Canada. Nineteen AZM(r) clinical isolates (one per patient; MIC, ≥2 μg/ml) were included in the study. Susceptibility profiles of these isolates to 11 antibiotics, molecular typing, characterization of macrolide resistance mechanisms, and penicillin-binding protein 2 (PBP2) patterns were determined for all the isolates. Two groups were defined based on AZM(r) level; group A isolates displayed high-level resistance (MIC, ≥2,048 μg/ml) due to mutations (A2143G) in the four copies of the 23S rRNA rrl gene, and group B isolates had moderate resistance to AZM (MICs, 2 to 8 μg/ml, C2599T mutation in the rrl gene), with a subgroup belonging to sequence type 3158 (ST3158) (n = 8), which also showed reduced susceptibility to 3GC (MICs, 0.12 to 0.25 μg/ml, PBP2 pattern XXXIV). This AZM(r) phenotype was not observed in previous provincial surveillance in 2008 (the ST3158 clone was found, with AZM MICs of 0.25 to 0.5 μg/ml associated with mtrR mutations). We hypothesized that the AZM mutant prevention concentration (MPC) in the ST3158 subpopulation we found in 2008 was higher than the MPC in wild-type isolates (AZM MIC, ≤0.031 μg/ml), increasing the chances of additional selection of AZM(r) mutations. Full AZM resistance is now emerging in this clone together with reduced susceptibility to 3GC, threatening the future efficacy of these antibiotics as therapeutic options for treatment of gonorrhea.

Treatment failure with 2 g of azithromycin (extended-release formulation) in gonorrhoea in Japan caused by the international multidrug-resistant ST1407 strain of Neisseria gonorrhoeae

OBJECTIVES

Antimicrobial resistance in Neisseria gonorrhoeae is a major public health concern globally. We report the first verified treatment failure of gonorrhoea with 2 g of azithromycin (extended-release formulation) in Japan and characteristics of the corresponding N. gonorrhoeae isolates.

METHODS

Pre- and post-treatment isolates (n = 4) were investigated by Etest for antimicrobial susceptibility. The isolates were examined for molecular epidemiology by multilocus sequence typing (MLST), N. gonorrhoeae multi-antigen sequence typing (NG-MAST) and multiple-locus variable-number tandem repeat analysis (MLVA), and for the presence of azithromycin resistance determinants (23S rRNA gene mutations, erm genes and mtrR mutations).

RESULTS

All isolates were resistant to azithromycin (MIC 4 mg/L) and ciprofloxacin, but remained susceptible to cefixime, ceftriaxone and spectinomycin. All isolates were assigned to MLST ST1901 and NG-MAST ST1407 and three of four isolates possessed MLVA profile 8-3-21-16-1. All isolates contained the previously described C2599T mutation (N. gonorrhoeae numbering) in all four 23S rRNA alleles and the previously described single-nucleotide (A) deletion in the mtrR promoter region.

CONCLUSIONS

This verified treatment failure occurred in a patient infected with an MLST ST1901/NG-MAST ST1407 strain of N. gonorrhoeae. While this international strain commonly shows resistance or decreased susceptibility to multiple antimicrobials, including extended-spectrum cephalosporins, the strain reported here remained fully susceptible to the latter antimicrobials. Hence, two subtypes of azithromycin-resistant gonococcal MLST ST1901/NG-MAST ST1407 appear to have evolved and to be circulating in Japan. Azithromycin should not be recommended as a single antimicrobial for first-line empirical treatment of gonorrhoea.

Antimicrobial susceptibility and molecular epidemiology of Neisseria gonorrhoeae in Germany

Antimicrobial drug resistance in Neisseria gonorrhoeae has become an increasing public health problem. Hence, surveillance of resistance development is of crucial importance to implement adequate treatment guidelines. Data on the spread of antibiotic resistance among gonococcal isolates in Germany, however, is scarce. In a resistance surveillance study conducted by the Paul Ehrlich Society for Chemotherapy between October 2010 and December 2011, 23 laboratories all over Germany were requested to send N. gonorrhoeae isolates to the study laboratory in Frankfurt am Main. Species verification was performed biochemically using ApiNH and with Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS). Antimicrobial susceptibility testing was performed using the Etest method. For molecular epidemiological analysis, N. gonorrhoeae strains were genotyped by means of N. gonorrhoeae multi-antigen sequence typing. A total of 213 consecutive gonococcal isolates were analyzed in this nationwide study. Applying EUCAST breakpoints, high resistance rates were found for ciprofloxacin (74%) and tetracycline (41%). Penicillin non-susceptibility was detected in 80% of isolates. The rate of azithromycin resistance was 6%, while all strains were susceptible to spectinomycin, cefixime, and ceftriaxone. Molecular typing of gonococcal isolates revealed a great heterogeneity of 99 different sequence types (ST), but ST1407 predominated (n=39). This is the first comprehensive German multi-centre surveillance study on antibiotic susceptibility and molecular epidemiology of N. gonorrhoeae with implications for antibiotic choice for treatment of gonorrhoea. The World Health Organization supports the concept that an efficacious treatment of gonorrhoea results in at least 95% of infections being cured. Accordingly, as spectinomycin is not available on the German market, only the third generation cephalosporins cefixime and ceftriaxone are regarded as valuable drugs for empirical treatment of gonorrhoea in Germany.

Clinical Efficacy of a Single Two Gram Dose of Azithromycin Extended Release for Male Patients with Urethritis

To clarify the clinical efficacy of a single oral 2 g dose of azithromycin extended-release for heterosexual male patients with urethritis, and the current antimicrobial sensitivity of Neisseria gonorrhoeae to azithromycin, a prospective clinical trial was conducted from 2011-2013. In patients with gonococcal urethritis, the eradication rate was 90.9% (30 of 33). The susceptibility rates of isolated Neisseria gonorrhoeae strains to ceftriaxone, spectinomycin, cefixime and azithromycin were 100%, 100%, 95.3% (41/43) and 37.2% (16/43), respectively. In the patients with nongonococcal urethritis, the eradication rate was 90.0% (45 of 50). The microbiological eradication rates for the pathogens were 90.9% (30/33) for Neisseria gonorrhoeae, 91.5% (43/47) for Chlamydia trachomatis, 71.4% (5/7) for Mycoplasma genitalium, and 100% (13/13) for Ureaplasma urealyticum. The main adverse event was diarrhea and its manifestation rate was 35.2% (32 of 120). The symptom of diarrhea was mostly temporary and resolved spontaneously. The conclusion was that the treatment regimen with a single oral 2 g dose of azithromycin extended-release would be effective for patients with urethritis. However, the antimicrobial susceptibilities of Neisseria gonorrhoeae and Mycoplasma genitalium should be carefully monitored because of possible treatment failure.

Characterization of azithromycin-resistant Neisseria gonorrhoeae isolated in Tokyo in 2005-2011

A total of 122 Neisseria gonorrhoeae isolated in the Tokyo metropolitan area in 2005-2011 were collected and analyzed by N. gonorrhoeae multiantigen sequence typing (NG-MAST) and for their susceptibility to azithromycin and ceftriaxone. All 122 strains were susceptible to ceftriaxone, but 8 strains were azithromycin-resistant, defined as an azithromycin MIC ≥ 1 μg/ml. The 8 azithromycin-resistant strains were in 6 NG-MAST types, 3 strains in NG-MAST type 1407 and each of the other 5 strains in a different NG-MAST type. NG-MAST type 1407 strains are multidrug-resistant and are disseminated worldwide.

Molecular approaches to enhance surveillance of gonococcal antimicrobial resistance

The best available data indicate that the world is heading towards a pandemic of extensively drug-resistant Neisseria gonorrhoeae. At the same time, clinical microbiology laboratories have moved away from using culture-based methods to diagnose gonorrhoea, thus undermining our ability to detect antimicrobial resistance (AMR) using current technologies. In this Opinion article, we discuss the problem of N. gonorrhoeae AMR, particularly emerging resistance to the cephalosporin ceftriaxone, outline current concerns about the surveillance of N. gonorrhoeae AMR and propose the use of molecular methods on a large scale to systematically enhance surveillance.

Gonococcal susceptibility to cephalosporins--Hawaii, 2003 to 2011

Among gonococcal isolates examined at the Hawaii State Laboratory Division from 2003 to 2011, the prevalence of elevated cefixime minimum inhibitory concentrations (MICs; ≥0.064 μg/mL) and elevated cefpodoxime MICs (≥0.19 μg/mL) increased over time. In contrast, few isolates exhibited elevated ceftriaxone MICs (≥0.094 μg/mL), and the prevalence of elevated ceftriaxone MICs did not change.

Point-of-care testing improves accuracy of STI care in an emergency department

OBJECTIVES

We aimed to examine the impact of a point-of-care (POC) test on overtreatment and undertreatment of sexually transmitted infections (STIs) by comparing treatment patterns for gonorrhoea (detected with nucleic acid amplification testing (NAAT)) with trichomoniasis (detected by POC test) for young women seen in an emergency department (ED).

METHODS

We reviewed the database of a quality improvement (QI) project that aims to improve follow-up care for STIs in the ED. Data included the test result and antibiotic given (if any) during visits by women age 14-21 for whom an STI test was ordered. We generated Shewhart control charts and compared overtreatment and undertreatment rates for gonorrhoea and trichomoniasis using χ(2) testing.

RESULTS

Of 1877 visits over 18 months, 8.8% of women had gonorrhoea and 16.5% had trichomoniasis. Overtreatment was higher for women with gonorrhoea than trichomoniasis (54% vs 23%, p<0.001). Overtreatment for gonorrhoea decreased from 58% to 47% (p<0.01) and overtreatment for trichomoniasis decreased from 24% to 18% (p<0.01), which corresponded to improvements in patient follow-up for the QI project. Undertreatment was higher for women with gonorrhoea than trichomoniasis (29% vs 21%, p=0.03), and did not change over time.

CONCLUSIONS

A POC test improves the accuracy of STI care in an ED compared with NAAT testing. An unanticipated benefit of QI efforts to improve patient follow-up is the observed decrease in antibiotic use in the ED. Given the ability of gonorrhoea to develop antibiotic resistance, future efforts should focus on development of an accurate POC test for gonorrhoea.

Neisseria gonorrhoeae antimicrobial resistance among men who have sex with men and men who have sex exclusively with women: the Gonococcal Isolate Surveillance Project, 2005-2010

BACKGROUND

Gonorrhea treatment has been complicated by antimicrobial resistance in Neisseria gonorrhoeae. Gonococcal fluoroquinolone resistance emerged more rapidly among men who have sex with men (MSM) than men who have sex exclusively with women (MSW).

OBJECTIVE

To determine whether N. gonorrhoeae urethral isolates from MSM were more likely than isolates from MSW to exhibit resistance to or elevated minimum inhibitory concentrations (MICs) of antimicrobials used to treat gonorrhea.

DESIGN

6 years of surveillance data from the Gonococcal Isolate Surveillance Project.

SETTING

Publicly funded sexually transmitted disease clinics in 30 U.S. cities.

PATIENTS

Men with a total of 34 600 episodes of symptomatic urethral gonorrhea.

MEASUREMENTS

Percentage of isolates exhibiting resistance or elevated MICs and adjusted odds ratios for resistance or elevated MICs among isolates from MSM compared with isolates from MSW.

RESULTS

In all U.S. regions except the West, isolates from MSM were significantly more likely to exhibit elevated MICs of ceftriaxone and azithromycin than isolates from MSW (P < 0.050). Isolates from MSM had a high prevalence of resistance to ciprofloxacin, penicillin, and tetracycline and were significantly more likely to exhibit antimicrobial resistance than isolates from MSW (P < 0.001).

LIMITATIONS

Sentinel surveillance may not be representative of all patients with gonorrhea. HIV status, travel history, and antimicrobial use data were missing for some patients.

CONCLUSION

Men who have sex with men are vulnerable to the emerging threat of antimicrobial-resistant N. gonorrhoeae. Because antimicrobial susceptibility testing is not routinely done in clinical practice, clinicians should monitor for treatment failures among MSM diagnosed with gonorrhea. Strengthened prevention strategies for MSM and new antimicrobial treatment options are needed.

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.

Antimicrobial susceptibility and genetic characteristics of Neisseria gonorrhoeae isolates from India, Pakistan and Bhutan in 2007-2011

BACKGROUND

Knowledge on antimicrobial drug resistance and genetic characteristics of Neisseria gonorrhoeae isolates circulating in India, Pakistan, and Bhutan is sorely lacking. In this paper, we describe the prevalence of antimicrobial resistance and molecular characteristics of N. gonorrhoeae isolates from India, Pakistan, and Bhutan in 2007-2011.

METHODS

Antimicrobial susceptibility and β-lactamase production were tested for 65 N. gonorrhoeae isolates from India (n=40), Pakistan (n=18) and Bhutan (n=7) using Etest methodology (eight antimicrobials) and nitrocefin solution, respectively. Resistance determinants, i.e. penA, mtrR, porB1b, gyrA, and parC, were sequenced. N. gonorrhoeae multiantigen sequence typing (NG-MAST) was performed for molecular epidemiology.

RESULTS

The highest resistance level was observed for ciprofloxacin (94%), followed by penicillin G (68%), erythromycin (62%), tetracycline (55%), and azithromycin (7.7%). All the isolates were susceptible to ceftriaxone, cefixime, and spectinomycin. Thirty-four (52%) of the isolates were producing β-lactamase. No penA mosaic alleles or A501-altered alleles of penicillin-binding protein 2 were identified. Forty-nine NG-MAST STs were identified, of which 42 STs have not been previously described worldwide.

CONCLUSIONS

Based on this study, ceftriaxone, cefixime, and spectinomycin can be used as an empirical first-line therapy for gonorrhoea in India, Pakistan, and Bhutan, whereas ciprofloxacin, penicillin G, tetracycline, erythromycin, and azithromycin should not be. It is imperative to strengthen the laboratory infrastructure in this region, as well as to expand the phenotypic and genetic surveillance of antimicrobial resistance, emergence of new resistance, particularly, to extended-spectrum cephalosporins, and molecular epidemiology.

Emergence of multidrug-resistant, extensively drug-resistant and untreatable gonorrhea

The new superbug Neisseria gonorrhoeae has retained resistance to antimicrobials previously recommended for first-line treatment and has now demonstrated its capacity to develop resistance to the extended-spectrum cephalosporin, ceftriaxone, the last remaining option for first-line empiric treatment of gonorrhea. An era of untreatable gonorrhea may be approaching, which represents an exceedingly serious public health problem. Herein, we review the evolution, origin and spread of antimicrobial resistance and resistance determinants (with a focus on extended-spectrum cephalosporins) in N. gonorrhoeae, detail the current situation regarding verified treatment failures with extended-spectrum cephalosporins and future treatment options, and highlight essential actions to meet the large public health challenge that arises with the possible emergence of untreatable gonorrhea. Essential actions include: implementing action/response plans globally and nationally; enhancing surveillance of gonococcal antimicrobial resistance, treatment failures and antimicrobial use/misuse; and improving prevention, early diagnosis and treatment of gonorrhea. Novel treatment strategies, antimicrobials (or other compounds) and, ideally, a vaccine must be developed.

Expedited partner therapy for sexually transmitted infections

PURPOSE OF REVIEW

In 2006, the Centers for Disease Control and Prevention recommended Expedited Partner Therapy (EPT) as a clinical option for assuring treatment of sex partners of persons infected with sexually transmitted infections. In this review, we provide an update on research, evaluation and efforts to increase EPT coverage. We also attend to EPT for gonorrhea in the context of antimicrobial resistance.

RECENT FINDINGS

Controlled trials in the United States and United Kingdom have presented increasing variety in intervention approaches. Trials and program evaluations typically demonstrate increased partner treatment rates, although only some studies show reductions in follow-up infection rates. Coverage has increased substantially, with over 30 states permitting EPT for chlamydial infection, gonorrhea, or both. The prospect of cephalosporin-resistant gonorrhea, however, raises the prospect that EPT may become less feasible as a partner treatment approach for gonorrhea patients.

SUMMARY

Clinicians should continue to be aware of the importance of partner managements for STD-infected patients, with EPT being an evidence-based intervention in that respect. The variety in EPT models provides alternatives that may suit some practices and venues. For clinicians seeing gonorrhea patients, effective counseling models - enhanced patient referral - should be closely examined in case oral treatment for gonorrhea becomes infeasible.

The ticking time bomb: escalating antibiotic resistance in Neisseria gonorrhoeae is a public health disaster in waiting

From a once easily treatable infection, gonorrhoea has evolved into a challenging disease, which in future may become untreatable in certain circumstances. International spread of extensively drug-resistant gonococci would have severe public health implications. It seems clear that under the current treatment pressure from extended-spectrum cephalosporins, and owing to Neisseria gonorrhoeae's remarkable evolutionary adaptability, further rise of ceftriaxone-resistant strains around the world is inevitable. Simply increasing the doses of extended-spectrum cephalosporins will likely prove ineffective in the long run, and has been a lesson learnt for all single-agent therapies used for gonorrhoea to date. We recommend that dual therapy, especially those consisting of extended-spectrum cephalosporins and azithromycin, be adopted more widely and complemented by strengthening of antimicrobial resistance surveillance. Unless there is urgent action at international and local levels to combat the problem of N. gonorrhoeae antimicrobial resistance, we are in for gloomy times ahead in terms of gonorrhoea disease and control.

The use of cephalosporins for gonorrhea: an update on the rising problem of resistance

INTRODUCTION

Over the last several years, Neisseria gonorrhoeae has developed decreased susceptibility to extended-spectrum cephalosporins worldwide. Gonococcal antimicrobial surveillance programs in multiple regions have documented the rise in N. gonorrhoeae isolates' minimum inhibitory concentrations to cephalosporins, and the first cases of ceftriaxone treatment failure have been reported. These developments have prompted the use of the term 'superbug' and concerns about the emergence of untreatable gonococcal infections.

AREAS COVERED

Since the publication of the last detailed review of the use of cephalosporins for gonorrhea in 2009, several new developments have occurred, which are detailed in this review. A variety of treatment strategies have been proposed in response to this 'superbug' threat, including increasing the dose or providing multiple doses of cephalosporins, multidrug therapy, rotating therapeutic regimens and individualized treatment based on susceptibility testing.

EXPERT OPINION

A robust public health response is needed that includes better diagnosis and treatment of pharyngeal gonorrhea, improved surveillance of antimicrobial resistance, informed treatment approaches and reduction of the global burden of gonococcal infections.

In vitro activity of the new fluoroketolide solithromycin (CEM-101) against a large collection of clinical Neisseria gonorrhoeae isolates and international reference strains, including those with high-level antimicrobial resistance: potential treatment option for gonorrhea?

Gonorrhea may become untreatable, and new treatment options are essential. We investigated the in vitro activity of the first fluoroketolide, solithromycin. Clinical Neisseria gonorrhoeae isolates and reference strains (n = 246), including the two extensively drug-resistant strains H041 and F89 and additional isolates with clinical cephalosporin resistance and multidrug resistance, were examined. The activity of solithromycin was mainly superior to that of other antimicrobials (n = 10) currently or previously recommended for gonorrhea treatment. Solithromycin might be an effective treatment option for gonorrhea.

Current and future challenges in the development of antimicrobial agents

Micro-organisms exist to survive. Even in the absence of antimicrobial agents, many have determinants of resistance that may be expressed phenotypically, should the need arise. With the advent of the antibiotic age, as more and more drugs were developed to treat serious infections, micro-organisms (particularly bacteria) rapidly developed resistance determinants to prevent their own demise.The most important determinants of resistance have been in the Gram-positive and Gram-negative bacteria. Among Gram-positive bacteria, methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE) and penicillin-resistant Streptococcus pneumoniae (PRSP) have taxed researchers and pharmaceutical companies to develop new agents that are effective against these resistant strains. Among the Gram-negative bacteria, extended-spectrum beta-lactamase (ESBL) enzymes, carbapenemases (CREs) and the so-called amp-C enzymes that may be readily transferred between species of enterobacteriaceae and other facultative species have created multi-drug resistant organisms that are difficult to treat. Other resistance determinants have been seen in other clinically important bacterial species such as Neisseria gonorrhoeae, Clostridium difficile, Haemophilus influenzae and Mycobacterium tuberculosis. These issues have now spread to fungal agents of infection.A variety of modalities have been used to stem the tide of resistance. These include the development of niche compounds that target specific resistance determinants. Other approaches have been to find new targets for antimicrobial activity, use of combination agents that are effective against more than one target in the cell, or new delivery mechanism to maximize the concentration of antimicrobial agents at the site of infection without causing toxicity to the host. It is important that such new modalities have been proved effective for clinical therapy. Animal models and non-mammalian systems have been developed to determine if new agents will reach sufficient concentrations at infection sites to predict clinical efficacy without toxicity. It will also be key to consider antimicrobial stewardship as an important component of the continuing battle to prevent the development of antimicrobial resistance.