Neisseria gonorrhoeae antimicrobial resistance (AMR) monthly UPDATES - June, 2019

Neisseria gonorrhoeae antimicrobial resistance (AMR) monthly UPDATES

June, 2019


Addressing Untreatable Gonorrhea: Resistance-Guided Therapy

Jeffrey D. Klausner, MD, MPH 

University of Minnesota, Center for Infectious Disease Research and Policy (CIDRAP) [Webinar]. Recorded 2019 June 18.


Reviews and Commentary

Now Is the Time to Implement Whole Genome Sequencing in the Global Antimicrobial Resistance Surveillance for Neisseria gonorrhoeae?

Golparian D, Unemo M. (Full Text)

EClinicalMedicine. 2019 Feb 18;7:11-12. doi: 10.1016/j.eclinm.2019.02.002. eCollection 2019 Jan.

Neisseria gonorrhoeae resistance driven by antibiotic use.

Dong HV, Klausner JD. (Full Text)

Nat Rev Urol. 2019 Jun 10. doi: 10.1038/s41585-019-0206-2. [Epub ahead of print]

Antimicrobial Resistance in Neisseria gonorrhoeae and Treatment of Gonorrhea.

Unemo M, Golparian D, Eyre DW. (Full Text)

Methods Mol Biol. 2019;1997:37-58. doi: 10.1007/978-1-4939-9496-0_3.


Gonorrhea and antimicrobial resistance (AMR) in Neisseria gonorrhoeae are major public health concerns globally. Dual antimicrobial therapy (mainly ceftriaxone 250-500 mg × 1 plus azithromycin 1-2 g × 1) is currently recommended in many countries. These dual therapies have high cure rates, have likely been involved in decreasing the level of cephalosporin resistance internationally, and inhibit the spread of AMR gonococcal strains. However, ceftriaxone-resistant strains are currently spreading internationally, predominately associated with travel to Asia. Furthermore, the first global treatment failure with recommended dual therapy was reported in 2016 and the first isolates with combined ceftriaxone resistance and high-level azithromycin resistance were reported in 2018 in the UK and Australia. New antimicrobials for treatment of gonorrhea are essential and, of the few antimicrobials in clinical development, zoliflodacin particularly appears promising. Holistic actions are imperative. These include an enhanced advocacy; prevention, early diagnosis, contact tracing, treatment, test-of-cure, and additional measures for effective management of anogenital and pharyngeal gonorrhea; antimicrobial stewardship; surveillance of infection, AMR and treatment failures; and intensified research, for example, regarding rapid molecular point-of-care detection of gonococci and AMR, novel AMR determinants, new antimicrobials, and an effective gonococcal vaccine, which is the only sustainable solution for management and control of gonorrhea.


Epidemiology and Surveillance

Ceftriaxone Reduced Susceptible Neisseria Gonorrhoeae in the Netherlands, 2009-2017: From Pena Mosaicism to A501t/V Non-Mosaicism.

de Laat MM, Wind CM, Bruisten SM, Dierdorp M, de Vries HJC, Schim van der Loeff MF, van Dam AP. (Full Text)

Sex Transm Dis. 2019 Jun 14. doi: 10.1097/OLQ.0000000000001031. [Epub ahead of print]



To compare molecular and epidemiological differences between ceftriaxone reduced susceptible (CRO-RS) and ceftriaxone susceptible (CRO-S) Neisseria gonorrhoeae (Ng), and to study the genetic relatedness of CRO-RS isolates.


Demographic and clinical data, and samples for cultures were routinely collected from gonorrhoea patients visiting the Amsterdam STI clinic in 2009-2017. NG-MAST and penA types were compared between CRO-RS and CRO-S Ng (frequency matched on year of isolation and sexual risk group). Minimum spanning trees (MST) were produced based on NG-MLVA genotypes.


We selected 174 CRO-RS isolates (MIC ≥0.064 mg/L) and 174 CRO-S isolates (MIC ≤0.016 mg/L). Demographic and clinical characteristics of patients were overall comparable between those infected with CRO-RS Ng and CRO-S Ng. However, CRO-RS isolates were more often collected from the pharyngeal site (OR 3.64, P <0.001), and patients with CRO-RS Ng were less often HIV and syphilis positive (OR 0.63, P=0.041 and OR 0.58, P=0.028 respectively). We identified 12 clusters based on NG-MLVA genotypes, including 3 large (>25 isolates) clusters predominantly containing CRO-RS isolates. Those from cluster 1 (n=32) were mostly from 2009-2012 (n=24; 75.0%), with a mosaic penA XXXIV pattern (n=27; 84.4%) and belonging to NG-MAST genogroup G1407 (n=24; 75.0%). Isolates from cluster 2 (n=29) were mostly from 2013-2015 (n=24; 82.7%), had a non-mosaic penA IX + A501T mutation (n=22; 75.9%) and NG-MAST G2400 (n=14; 48.3%). Most isolates from cluster 3 (n=37) were from 2015-2017 (n=26; 70.2%), had a non-mosaic penA IV + A501V mutation (n=24; 64.9%) and NG-MAST G2318 (n=22; 59.5%).


We observed a shift in the predominant penA (from mosaic towards non-mosaic plus A501T/V mutation), NG-MAST and NG-MLVA types among CRO-RS Ng over time. This indicates a successive spread of different CRO-RS Ng clones.

High prevalence of TEM-135 expression from the Asian plasmid in penicillinase-producing Neisseria gonorrhoeae from Hangzhou, China.

Yan J, Zhang J, van der Veen S. (Full Text)

Int J Antimicrob Agents. 2019 Jun 13. pii: S0924-8579(19)30165-7. doi: 10.1016/j.ijantimicag.2019.06.012. [Epub ahead of print]


Penicillinase-producing Neisseria gonorrhoeae (PPNG) expressing the TEM-135 variant are a global public health concern because this variant only requires a single amino-acid substitution to develop into an extended-spectrum β-lactamase. The aim of this study was to investigate the epidemiology of blaTEM-135 in 505 isolates from Hangzhou, China, over the periods 2011-12 and 2015-17. Investigation by nitrocefin test and mismatch amplification PCR showed that 41% of the isolates were PPNG and 37% of these PPNG isolates contained the blaTEM-135 allele. Further PCR-based plasmid typing showed that blaTEM-135 was predominantly expressed from the Asian plasmid (94%). PPNG isolates consisted of three major clusters, namely Asian plasmid/blaTEM-135 (35%), Asian plasmid/blaTEM-1 (32%) and African plasmid/blaTEM-1 (28%), which showed significant differences in penicillin MICs tested by agar dilution method. Therefore representative strains were investigated by quantitative real-time PCR (plasmid copy number and blaTEM gene expression), Western analysis (TEM levels and TEM stability) and in vivo β-lactamase activity assays to elucidate the cause. Overall, strains of the Asian plasmid/blaTEM-135 cluster showed the highest β-lactamase activity, which was explained by higher blaTEM gene expression (Asian versus African plasmid) and higher TEM stability (TEM-135 versus TEM-1). In conclusion, the blaTEM-135 allele is commonly present on the Asian plasmid in PPNG isolates from Hangzhou. The PPNG strain cluster containing the Asian plasmid and blaTEM-135 showed the highest penicillin MICs, which might explain its abundance in the Hangzhou population.

A Whole-genome Sequencing Analysis of Neisseria gonorrhoeae Isolates in China: An Observational Study.

Peng JP, Yin YP, Chen SC, Yang J, Dai XQ, Zheng HP, Gu WM, Zhu BY, Yong G, Zhong N, Hu LH, Cao WL, Zheng ZJ, Wang F, Zhi Q, Zhang C, Xiu LS, Liu B, Dong J, Sun LL, Zhu YF, Chen XS, Jin Q. (Full Text)

EClinicalMedicine. 2019 Feb 14;7:47-54. doi: 10.1016/j.eclinm.2019.01.010. eCollection 2019 Jan.



Tracking the spread of the Neisseria gonorrhoeae strains with decreased susceptibility or resistance to cephalosporins is a major priority for global surveillance programmes. Whole-genome sequencing (WGS) has been widely used by increasing countries in North America, Europe, and Pacific to determine the decreased susceptible or resistance determinants of Neisseria gonorrhoeae, track the spread of these determinants throughout the gonococcal population at national or regional level. However, no studies to date have examined the genomic epidemiology of gonorrhea in Asia where the antimicrobial resistant strains of Neisseria gonorrhoeae appears to have emerged before disseminating the strains globally.


We obtained clinical isolates and data from the China Gonococcal Resistance Surveillance Programme (China-GRSP) from 2012 to 2013. We sequenced the genomes of 435 clinical isolates of Neisseria gonorrhoeae, including 112 (25.6%) isolates with decreased susceptibility to ceftriaxone (Cfx-DS). We assessed the association between antimicrobial resistance genotype and phenotype. We also compared our data with the whole genome data of the isolates from the USA and the UK in the GenBank.


The most prevalent MLST STs in our gonococcal population were MLST ST7827 (n = 74), followed by ST7365 (n = 58), ST1600 (n = 38), ST7367 (n = 35), and ST7363 (n = 29). MLST ST1901 which was reported as the predominant ST in the US was not found in our population. A total of 2512 strains, including additional 2077 published NG strains, were further included for phylogenetic analysis. It generated two distinct lineages - lineage 1 and lineage 2. Analysis of MLST ST1901 in the database indicate that most of MLST ST1901 isolates in the lineage2.6 were Cfx-DS isolates while all isolates in the lineage 2.1 were sensitive to ceftriaxone (77/110 vs. 0/13; p < 0.001). ST1901/lineage 2.6 is a ceftriaxone resistant clone which cannot distinguished by MLST genotyping. In the isolates from our study, the MICs of ceftriaxone for ST7363/lineage 2.6 isolates ranged from 0.008-0.125 mg/L (mean ± SD; 0.054 ± 0.043 mg/L) while those for ST7363/lineage 2.8 isolates ranged from 0.032-0.250 mg/L (0.134 ± 0.085 mg/L). All ST7363/lineage 2.8 isolates contained penA mosaic alleles.


To our knowledge, current study is the first WGS-based analysis of gonococcal population at national level in Asia. China harbors the different predominant clones associated with decreased susceptibility to ceftriaxone from those clones circulated in other regions. The findings from the study can be not only used as baseline data for future studies in China but also contributable to our understanding on spread of N. gonorrhoeae and its resistant strains at regional and global levels.


The Chinese Academy Medical Sciences (CAMS) Initiative for Innovative Medicine.

Modulation effect of vaginal mucosal microflora and susceptibility to Neisseria gonorrhoeae infections: a systematic review and meta-analysis.

Zeng J, Yang R, He W, Zhong X, Liu W, Zhu H, Zhang X, Luo Q. (Full Text)

Arch Gynecol Obstet. 2019 Jun 7. doi: 10.1007/s00404-019-05200-1. [Epub ahead of print]



The vaginal microbiota may modulate susceptibility to Neisseria gonorrhea (NG) infections. The objective of this meta-analysis was to evaluate the association between these NG infections and the vaginal microbiota.


A systematic review and meta-analysis was conducted to investigate the correlation of vaginal microbiota and NG risk. Primary sources of the reviewed studies were from inception through December 2018. Vaginal mucosa microflora were dichotomized into high-Lactobacillus vaginal microbiota and low-Lactobacillus vaginal microbiota (LL-VMB), using either Nugent score, Amsel's criteria, presence of clue cells or 16S rRNA gene sequencing.


A total of 8 studies qualified for inclusion in this meta-analysis. LL-VMB could be regarded as worse prognostic factor, and the pooled OR was 1.33 (95% CI 1.02, 1.73; P = 0.04, I2 = 44%). LL-VMB was associated with a significantly higher susceptibility of NG. Trend for the sensitive analysis was consistence with the primary outcome. Significant publication bias was not detected by the funnel plot.


In conclusion, the systematic review and meta-analysis has demonstrated that LL-VMB was significantly associated with a high NG susceptibility.

Emergence and spread of ciprofloxacin-resistant Neisseria gonorrhoeae in New South Wales, Australia: lessons from history.

Hanrahan JK, Hogan TR, Buckley C, Trembizki E, Mitchell H, Lau CL, Whiley DM, Lahra MM. (Full Text)

J Antimicrob Chemother. 2019 Jun 6. pii: dkz182. doi: 10.1093/jac/dkz182. [Epub ahead of print]



Our aim was to investigate the emergence and spread of ciprofloxacin resistance in clinical Neisseria gonorrhoeae isolates in New South Wales, Australia, from the first reported case in 1991 until ciprofloxacin resistance was sustained at or above the WHO threshold for treatment change of 5% (1999), to inform future strategies for controlling gonococcal antimicrobial resistance.


The index isolate and all subsequent clinical isolates of ciprofloxacin-resistant N. gonorrhoeae in New South Wales from 1991 to 1999 were genotyped using a previously described method on the Agena MassARRAY iPLEX platform. Region of acquisition data, where available, were used to determine whether cases were travel associated.


In New South Wales, of the 325 ciprofloxacin-resistant N. gonorrhoeae isolates reported from 1991 to 1999, 98% (320/325) were able to be recovered and 100% (320/320) were genotyped. There were 66 different genotypes, comprising 1-99 isolates each. Notably no single clone was found to account for ciprofloxacin resistance being sustained in the population, with considerable variability in genotype prevalence observed throughout the study period. A total of 65% (209/320) of genotyped isolates had information regarding the likely place of acquisition; of these, 44% (93/209) were associated with overseas travel or sexual contact with an overseas visitor. The first ciprofloxacin-resistant N. gonorrhoeae in New South Wales was associated with travel to Thailand. Index cases of each resistant genotype were significantly more likely to have been acquired overseas (51.5%), predominantly in Asia (45%, 30/66).


The continued importation of multiple genotypes, rather than the expansion of a single genotype, led to ciprofloxacin-resistant N. gonorrhoeae being established in New South Wales.

Neisseria gonorrhoeae ciprofloxacin-resistant strains were associated with Chlamydia trachomatis coinfection.

Corich L, Campisciano G, Zanotta N, Monasta L, Petix V, Favero B, Colli C, Seta F, Comar M. 

Future Microbiol. 2019 May;14:653-660. doi: 10.2217/fmb-2019-0015. Epub 2019 May 29.


Aim: This study aims to characterize circulating strains to predict their relationship with sexually transmitted microorganisms, Chlamydia trachomatis, HIV, HCV, Treponema pallidum, HPV, Mycoplasmas, in an Italian multiethnic area, which has revealed a recent increase of Neisseria gonorrhoeae first-line antibiotic resistance. Materials & methods: We performed N. gonorrhoeae multiantigen sequence typing and the N. gonorrhoeae sequence typing for antimicrobial resistance. Results: We identified mutations in genes conferring resistance to cephalosporins, macrolides, fluoroquinolones through por and tbpB loci, and we reported new combinations of already known alleles. N. gonorrhoeae resistance to ciprofloxacin was associated with C. trachomatis coinfection. Conclusion: This study's data proved the utility of a routine N. gonorrhoeae molecular characterization to monitor the evolution of antibiotic resistance and to detect the most effective clinical treatment.

Detection of tet(M) in high-level tetracycline-resistant Neisseria gonorrhoeae.

Pitt R, Sadouki Z, Town K, Fifer H, Mohammed H, Hughes G, Woodford N, Cole MJ. (Full Text)

J Antimicrob Chemother. 2019 Jul 1;74(7):2115-2116. doi: 10.1093/jac/dkz130.

Genomic Characterization of Gonococci from Different Anatomic Sites, Italy, 2007-2014.

Carannante A, Ciammaruconi A, Vacca P, Anselmo A, Fillo S, Palozzi AM, Fortunato A, Lista F, Stefanelli P. (Full Text)

Microb Drug Resist. 2019 Jun 20. doi: 10.1089/mdr.2018.0371. [Epub ahead of print]


In recent decades, Neisseria gonorrhoeae has developed resistance to several antimicrobial classes. Molecular epidemiology approaches are useful for detecting emerging, often resistant, gonococcal clones. In this study, 67 N. gonorrhoeae isolates from different anatomic sites, collected over 8 years in Italy, were analyzed by whole genome sequencing (WGS). WGS was performed using the Illumina NextSeq 500 platform. Phylogenetic analysis was based on core single nucleotide polymorphism (SNP) and core genome multilocus sequence typing (cgMLST). N. gonorrhoeae multi-antigen sequence typing (NG-MAST), MLST, and N. gonorrhoeae sequence typing for antimicrobial resistance (NG-STAR) were carried out in silico using WGS data. Antimicrobial susceptibility against a four-drug panel was evaluated using a gradient diffusion method. Overall, gonococci clustered in accordance with NG-MAST, MLST, NG-STAR, and antimicrobials susceptibility profiles, but not with the site of isolation, HIV status, and patient sexual orientation. Phylogenetic analysis identified nine clades: two of them were the predominant and including gonococci of G1407 and G2400 genogroups.

Use of whole genome sequencing for the molecular comparison of Neisseria gonorrhoeae isolates with decreased susceptibility to extended spectrum cephalosporins from two geographically different regions in America.

Gianecini RA, Zittermann S, Oviedo C, Galas M, Ramon Pardo P, Allen VG, Galarza P, Melano RG. (Full Text)

Sex Transm Dis. 2019 Apr 24. doi: 10.1097/OLQ.0000000000001011. [Epub ahead of print]



Neisseria gonorrhoeae isolates with reduced susceptibility or resistance to the recommended first-line antimicrobial therapy have been described in several countries. The purpose of this study was to use genome analyses to compare the molecular characteristics of N. gonorrhoeae isolates with decreased susceptibility to extended-spectrum cephalosporin (ESC) from Ontario, Canada, and Argentina.


A total of 128 N. gonorrhoeae isolates, collected in 2015, were included. The susceptibility to penicillin G, tetracycline, ciprofloxacin, cefixime, ceftriaxone and azithromycin was determined using the agar dilution method. Isolates were subjected to whole genome sequencing, and an in silico analysis was performed to identify antimicrobial resistance determinants and for genotyping.


Decreased susceptibility to ESC was mainly associated with penA mosaic allele 34.001, together with an mtrR promoter A deletion and porB1b alterations G120K/A121N. N. gonorrhoeae multiantigen sequence typing (NG-MAST) ST1407 or closely related genotypes were identified circulating in both regions.


An international multi-drug resistant clone of N. gonorrhoeae was associated with decreased susceptibility to ESC in two different regions in America. Evidence of clonal dissemination of the organism in some regions, suggest that the strength of surveillance programs and establishment of collaborative projects are essential.


Novel detection strategies and diagnostics

Using the genetic characteristics of Neisseria gonorrhoeae strains with decreased susceptibility to cefixime to develop a molecular assay to predict cefixime susceptibility

Deng XM, Allan-Blitz LT, and Klausner JD. (Full Text)

Sexual Health. 2019 June 24. 


Background: In the last two decades, gonococcal strains with decreased cefixime susceptibility and cases of clinical treatment failure have been reported worldwide. Gonococcal strains with a cefixime minimum inhibitory concentration (MIC)
>=0.12 mg mL-1 are significantly more likely to fail cefixime treatment than strains with an MIC <0.12 mg mL-1. Various researchers have described the molecular characteristics of gonococcal strains with reduced cefixime susceptibility, and many have proposed critical molecular alterations that contribute to this decreased susceptibility.

Methods: A systematic review of all published articles in PubMed through 1 November 2018 was conducted that report findings on the molecular characteristics and potential mechanisms of resistance for gonococcal strains with decreased cefixime susceptibility. The findings were summarised and suggestions were made for the development of a molecular-based cefixime susceptibility assay.

Results: The penicillin-binding protein 2 (PBP2)

encoded by the penA gene is the primary target of cefixime antimicrobial activity. Decreased cefixime susceptibility is conferred by altered penA genes with mosaic substitute sequences from other Neisseria (N.) species (identifiable by alterations at amino acid position 375–377) or by non-mosaic penA genes with at least one of the critical amino acid substitutions at positions 501, 542 and 551. Based on this review of 415 international cefixime decreased susceptible N. gonorrhoeae isolates, the estimated sensitivity for an assay detecting the aforementioned amino acid alterations would be 99.5% (413/415).

Conclusions: Targeting mosaic penA and critical amino acid substitutions in non-mosaic penA are necessary and may be sufficient to produce a robust, universal molecular assay to predict cefixime susceptibility.

Impact of species diversity on the design of RNA-based diagnostics for antibiotic resistance in Neisseria gonorrhoeae.

Wadsworth CB, Sater MRA, Bhattacharyya RP, Grad YH. (Full Text)

Antimicrob Agents Chemother. 2019 May 28. pii: AAC.00549-19. doi: 10.1128/AAC.00549-19. [Epub ahead of print]


Quantitative assessment of antibiotic-responsive RNA transcripts holds promise for a rapid point of care (POC) diagnostic tool for antimicrobial susceptibility testing (AST). These assays aim to distinguish susceptible and resistant isolates by transcriptional differences upon drug exposure. However, an often-overlooked dimension of designing these tests is that the genetic diversity within a species may yield differential transcriptional regulation independent of resistance phenotype. Here, we use a phylogenetically diverse panel of Neisseria gonorrhoeae and transcriptome profiling coupled with RT-qPCR to test this hypothesis, to identify azithromycin responsive transcripts and evaluate their potential diagnostic value, and to evaluate previously reported diagnostic markers for ciprofloxacin resistance (porB and rpmB). Transcriptome profiling confirmed evidence of genetic distance and population structure impacting transcriptional response to azithromycin. Taking this into account, we found azithromycin-responsive transcripts overrepresented in susceptible strains compared to resistant strains, and selected four candidate diagnostic transcripts (rpsO, rplN, omp3, and NGO1079) that were the most significantly differentially regulated between phenotypes across drug exposure. RNA signatures for these markers categorically predicted resistance in 19/20 cases, with the one incorrect categorical assignment for an isolate at the threshold of reduced susceptibility. Finally, we found that porB and rpmB expression were not uniformly diagnostic of ciprofloxacin resistance in a panel of isolates with unbiased phylogenetic sampling. Overall, our results suggest that RNA signatures as a diagnostic tool are promising for future POC diagnostics; however, development and testing should consider representative genetic diversity of the target pathogen.

Prediction of Minimum Inhibitory Concentrations of Antimicrobials for Neisseria gonorrhoeae Using Whole-Genome Sequencing.

Eyre DW, Golparian D, Unemo M. (Full Text)

Methods Mol Biol. 2019;1997:59-76. doi: 10.1007/978-1-4939-9496-0_4.


Bacterial whole-genome sequencing is now increasingly available to researchers, reference laboratories and individual healthcare institutions. It can be possible to predict antimicrobial minimum inhibitory concentrations (MICs) for Neisseria gonorrhoeae using sequencing data, for many antimicrobials within one or two MIC doubling dilutions of the phenotypic value. With emerging rapid sequencing technologies, it may be possible in future to predict antimicrobial resistance faster than existing culture-based methods. Sequencing also provides insights into the genetic mechanisms underlying antimicrobial resistance, their spread in time and space, as well as the molecular epidemiology of the gonococcal strains.


Novel antibiotics, mechanisms, vaccine, and other advances

Solithromycin versus ceftriaxone plus azithromycin for the treatment of uncomplicated genital gonorrhoea (SOLITAIRE-U): a randomised phase 3 non-inferiority trial.

Chen MY, McNulty A, Avery A, Whiley D, Tabrizi SN, Hardy D, Das AF, Nenninger A, Fairley CK, Hocking JS, Bradshaw CS, Donovan B, Howden BP, Oldach D; Solitaire-U Team. (Full Text)

Lancet Infect Dis. 2019 Jun 10. pii: S1473-3099(19)30116-1. doi: 10.1016/S1473-3099(19)30116-1. [Epub ahead of print]



Antibiotic-resistant gonorrhoea represents a global public health threat, and new therapies are needed. We aimed to compare the efficacy and safety of solithromycin, a fourth generation macrolide, with ceftriaxone plus azithromycin for the treatment of gonorrhoea.


We did an open-label, multicentre, non-inferiority trial of patients aged 15 years or older with uncomplicated untreated genital gonorrhoea at two sites in Australia and one site in the USA. Patients were randomly assigned (1:1) to receive single dose oral solithromycin 1000 mg or intramuscular ceftriaxone 500 mg plus oralazithromycin 1000 mg. Neisseria gonorrhoeae cultures were obtained at baseline and test of cure (day 7 ± 2). The primary outcome was the proportion of patients with eradication of genital N gonorrhoeae based on culture at test of cure, assessed in the microbiological intention-to-treat (mITT) population, which included all randomly assigned patients who received any dose of study drug and had a positive genital culture for N gonorrhoeae at baseline. Non-inferiority of solithromycin was to be concluded if the lower limit of the 95% CI for the between-group differences was greater than -10%. Safety was analysed in all patients who received any dose of study drug. This trial is registered with, number NCT02210325.


Between Sept 3, 2014, and Aug 27, 2015, 262 patients were randomly assigned and 261 received treatment (130 in the solithromycin group and 131 in the ceftriaxone plus azithromycin group). In the mITT population, 99 (80%) of 123 patients in the solithromycin group and 109 (84%) of 129 patients in the ceftriaxone plus azithromycin group had N gonorrhoeae eradication at test of cure (difference -4·0%, 95% CI -13·6 to 5·5), thus solithromycin did not meet the criterion for non-inferiority at the prespecified -10% margin. The frequency of adverse events was higher in the solithromycin group than the ceftriaxone plus azithromycin group (69 [53%] of 130 patients vs 45 [34%] of 131 patients), the most common of which were diarrhoea (31 [24%] of 130 patients vs 20 [15%] of 131 patients), and nausea (27 [21%] of 130 patients vs 15 [11%] of 131 patients).


Solithromycin as a single 1000 mg dose is not a suitable alternative to ceftriaxone plus azithromycin as first-line treatment for gonorrhoea. If insufficient duration of solithromycin exposure at the infection site in a subset of individuals was the reason for treatment failures, this might be adequately addressed with dose adjustment. However, any further trials with longer dosing need to consider the potential risk of gastrointestinal effects and liver enzyme elevations.


Cempra Pharmaceuticals.

In vitro activity of mecillinam and nitroxoline against Neisseria gonorrhoeae - re-purposing old antibiotics in the multi-drug resistance era.

Fuchs F, Wille J, Hamprecht A, Parcina M, Lehmann C, Schwarze-Zander C, Seifert H, Higgins PG. (Full Text)

J Med Microbiol. 2019 Jun 4. doi: 10.1099/jmm.0.001014. [Epub ahead of print]


In 2018, the European Centre for Disease Prevention and Control reported the first cases of extensively drug-resistant Neisseria gonorrhoeae infections in Europe. Seeking new options for antimicrobial therapy we investigated the susceptibility of N. gonorrhoeae to nitroxoline (NIT) and mecillinam (MCM), both of which are currently only indicated to treat uncomplicated urinary tract infections. Clinical N. gonorrhoeae isolates with non-susceptibility to penicillin from two German medical centres were included (n =27). Most isolates were also non-susceptible to a range of other anti-gonococcal antimicrobials (cefotaxime, ciprofloxacin, azithromycin, tetracycline). All isolates were further characterized by multi-locus sequence typing. MICs of penicillin and cefotaxime were determined by agar gradient diffusion. Production of penicillinase was tested by cefinase disk test. Susceptibility of MCM was investigated by agar dilution, NIT by agar dilution and disk diffusion. Penicillin MICs ranged from 0.125 to 64 mg l and MICs of cefotaxime ranged from < 0.016 to 1 mg. Five isolates were penicillinase-producers. MICs of MCM ranged from 16 to > 128 mg whereas MICs of NIT ranged from 0.125 to 2 mg. NIT disk diffusion (median zone diameter 32 mm) correlated well with results from agar dilution. We demonstrated excellent in vitro activity of NIT against clinical N. gonorrhoeae isolates with non-susceptibility to standard anti-gonococcal antibiotics. MCM activity was unsatisfactory. Correlation of agar dilution and disk diffusion in NIT susceptibility testing is an important aspect with potential clinical implications.

Antimicrobial Blue Light Inactivation of Neisseria gonorrhoeae: Roles of Wavelength, Endogenous Photosensitizer, Oxygen, and Reactive Oxygen Species.

Wang Y, Ferrer-Espada R, Baglo Y, Gu Y, Dai T. (Full Text)

Lasers Surg Med. 2019 Jun 3. doi: 10.1002/lsm.23104. [Epub ahead of print]



The aim of this study was to investigate the efficacy, safety, and mechanism of action of antimicrobial blue light (aBL) for the inactivation of Neisseria gonorrhoeae, the etiological agent of gonorrhea.


The susceptibilities of N. gonorrhoeae (ATCC 700825) in planktonic suspensions to aBL at 405- and 470-nm wavelengths were compared. The roles of oxygen in the anti-gonococcal activity of aBL were studied by examining the effects of hypoxic condition (blowing N2 ) on the anti-gonococcal efficiency of 405-nm aBL. The presence, identification, and quantification of endogenous photosensitizers in N. gonorrhoeae cells and human vaginal epithelial cells (VK2/E6E7 cells) were determined using fluorescence spectroscopy and ultra-performance liquid chromatography (UPLC). Finally, the selectivity of aBL inactivation of N. gonorrhoeae over the host cells were investigated by irradiating the co-cultures of N. gonorrhoeae and human vaginal epithelial cells using 405-nm aBL.


About 3.12-log10 reduction of bacterial colony forming units (CFU) was achieved by 27 J/cm 2 exposure at 405 nm, while about 3.70-log10 reduction of bacterial CFU was achieved by 234 J/cm2 exposure at 470 nm. The anti-gonococcal efficacy of 405-nm aBL was significantly suppressed under hypoxic condition. Spectroscopic and UPLC analyses revealed the presence of endogenous porphyrins and flavins in N. gonorrhoeae. The concentrations of endogenous photosensitizers in N. gonorrhoeae (ATCC 700825) cells were more than 10 times higher than those in the VK2/E6E7 cells. In the co-cultures of N. gonorrhoeae and VK2/E6E7 cells, 405-nm aBL at 108 J/cm2 preferentially inactivated N. gonorrhoeae cells while sparing the vaginal epithelial cells.


aBL at 405-nm wavelength is more effective than 470-nm wavelength in inactivating N. gonorrhoeae while sparing the vaginal epithelial cells. Reactive oxygen species generated from the photochemical reactions between aBL and endogenous photosensitizers play a vital role in the anti-gonococcal activity of 405-nm aBL. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

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

Ross JD, Harding J, Duley L, Montgomery AA, Hepburn T, Tan W, Brittain C, Meakin G, Sprange K, Thandi S, Jackson L, Roberts T, Wilson J, White J, Dewsnap C, Cole M, Lawrence T. (Full Text)

Health Technol Assess. 2019 May;23(20):1-104. doi: 10.3310/hta23200.



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.


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


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


Fourteen sexual health clinics in England.


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).


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


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.


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.


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).


Loss to follow-up was 17% but was similar in both treatment arms. Twelve percent 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.


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.


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.


Current Controlled Trials ISRCTN51783227.


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.


Gonorrhoea is a common infection, spread by having sex, that causes genital pain and discomfort. In women it can lead to pelvic inflammation and infertility, and in men it can lead to swelling and pain in the testicles. Currently, an antibiotic called ceftriaxone is used to treat gonorrhoea. However, there is evidence that this is becoming less effective over time and it could stop curing patients with gonorrhoea within the next few years. In this study, we wanted to find out if another antibiotic called gentamicin is as good as ceftriaxone in the treatment of gonorrhoea and whether or not gentamicin could be used to treat gonorrhoea if ceftriaxone stops being effective. We recruited 720 adults with gonorrhoea and randomly allocated them (by chance) to receive treatment with an injection of either gentamicin (240 mg) or ceftriaxone (500 mg). They all also received a single dose of azithromycin (1 g) taken by mouth. Overall, 98% of participants given ceftriaxone had their gonorrhoea cured, compared with 91% of participants given gentamicin, a difference of 7%. Therefore, it is likely that doctors will continue to use ceftriaxone (plus azithromycin) as the preferred treatment. Gentamicin did have a cure rate of 94% for genital gonorrhoea and so it might be useful when ceftriaxone is not available or appropriate to use. Cure rates using gentamicin were lower than cure rates using ceftriaxone for gonorrhoea infecting the rectum (90%) and throat (80%), so it may be less useful for patients with infections at these sites. We also found that gentamicin is likely to cost the NHS more than ceftriaxone. Gentamicin caused few side effects and seems to be as safe as ceftriaxone, which is reassuring.

In vitro activity of the ketolide cethromycin in multidrug-resistant clinical Neisseria gonorrhoeae isolates and international reference strains.

Jacobsson S, Alirol E, Unemo M. (Full Text)

J Chemother. 2019 May 20:1-6. doi: 10.1080/1120009X.2019.1615724. [Epub ahead of print]


Antimicrobial resistance in Neisseria gonorrhoeae is a major public health problem, which compromises the treatment of gonorrhoea globally. We evaluated the in vitro activity of the ketolide cethromycin against a large panel of clinical gonococcal isolates and international reference strains (n = 254), including numerous multidrug-resistant and extensively drug-resistant isolates. Cethromycin showed potent in vitro activity against most of the gonococcal isolates with the following modal MIC, MIC50 and MIC90: 0.064 mg/L, 0.125 mg/L and 0.5 mg/L, respectively. However, cross-resistance between azithromycin and cethromycin was identified (Spearman's rank correlation coefficient 0.917) and isolates displaying high-level resistance to azithromycin (MIC >256 mg/L; n = 9) also showed high MICs of cethromycin (32-256 mg/L). In conclusion, the cross-resistance with azithromycin indicates that cethromycin may not be considered for empirical first-line monotherapy of gonorrhoea. However, cethromycin might be valuable in combination antimicrobial therapy and for second-line therapy e.g. for cases with ceftriaxone resistance or allergy.

Complement alone drives efficacy of a chimeric antigonococcal monoclonal antibody.

Gulati S, Beurskens FJ, de Kreuk BJ, Roza M, Zheng B, DeOliveira RB, Shaughnessy J, Nowak NA, Taylor RP, Botto M, He X, Ingalls RR, Woodruff TM, Song WC, Schuurman J, Rice PA, Ram S.

PLoS Biol. 2019 Jun 19;17(6):e3000323. doi: 10.1371/journal.pbio.3000323. [Epub ahead of print]


Multidrug-resistant Neisseria gonorrhoeae is a global health problem. Monoclonal antibody (mAb) 2C7 recognizes a gonococcal lipooligosaccharide epitope that is expressed by >95% of clinical isolates and hastens gonococcal vaginal clearance in mice. Chimeric mAb 2C7 (human immunoglobulin G1 [IgG1]) with an E430G Fc modification that enhances Fc:Fc interactions and hexamerization following surface-target binding and increases complement activation (HexaBody technology) showed significantly greater C1q engagement and C4 and C3 deposition compared to mAb 2C7 with wild-type Fc. Greater complement activation by 2C7-E430G Fc translated to increased bactericidal activity in vitro and, consequently, enhanced efficacy in mice, compared with "Fc-unmodified" chimeric 2C7. Gonococci bind the complement inhibitors factor H (FH) and C4b-binding protein (C4BP) in a human-specific manner, which dampens antibody (Ab)-mediated complement-dependent killing. The variant 2C7-E430G Fc overcame the barrier posed by these inhibitors in human FH/C4BP transgenic mice, for which a single 1 μg intravenous dose cleared established infection. Chlamydia frequently coexists with and exacerbates gonorrhea; 2C7-E430G Fc also proved effective against gonorrhea in gonorrhea/chlamydia-coinfected mice. Complement activation alone was necessary and sufficient for 2C7 function, evidenced by the fact that (1) "complement-inactive" Fc modifications that engaged Fc gamma receptor (FcγR) rendered 2C7 ineffective, nonetheless; (2) 2C7 was nonfunctional in C1q-/- mice, when C5 function was blocked, or in C9-/- mice; and (3) 2C7 remained effective in neutrophil-depleted mice and in mice treated with PMX205, a C5a receptor (C5aR1) inhibitor. We highlight the importance of complement activation for antigonococcal Ab function in the genital tract. Elucidating the correlates of protection against gonorrhea will inform the development of Ab-based gonococcal vaccines and immunotherapeutics.