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

Neisseria gonorrhoeae antimicrobial resistance (AMR) monthly UPDATES

January, 2019

New Guideline

British Association for Sexual Health and HIV national guideline for the management of infection with Neisseria gonorrhoeae (2019).

Helen Fifer, John Saunders, Suneeta Soni, S Tariq Sadiq, Mark FitzGerald. (Full Text)

Epidemiology and Surveillance 

Australian Gonococcal Surveillance Programme Annual Report, 2016.

Lahra MM, Enriquez R. (Full Text)

Commun Dis Intell (2018). 2018;42. pii: S2209-6051(18)00013-1.


The Australian Gonococcal Surveillance Programme (AGSP) has continuously monitored antimicrobial resistance in clinical isolates of Neisseria gonorrhoeae from all states and territories since 1981. In 2016, there were 6,378 clinical isolates of gonococci from public and private sector sources tested for in vitro antimicrobial susceptibility by standardised methods. Current treatment recommendations for the majority of Australia is a dual therapeutic strategy of ceftriaxone and azithromycin. Decreased susceptibility to ceftriaxone (Minimum Inhibitory Concentration or MIC value 0.06-0.125 mg/L) was found nationally in 1.7% of isolates, similar to that reported in the AGSP Annual Report 2015 (1.8%). The highest proportions were reported from Queensland and Tasmania (3.7% and 3.6% respectively). Resistance to azithromycin (MIC value ≥1.0 mg/L) was found nationally in 5.0% of isolates, double the proportion reported in 2015. The highest proportions were reported from South Australia (19.5%), Tasmania (14.3%) and urban Western Australia (7.6%). High level resistance to azithromycin (MIC value ≥256 mg/L) was again reported in 5 strains. Nationally in 2016, 4 from Victoria and 1 in South Australia. There was no reported azithromycin resistance in remote Northern Territory. The proportion of strains resistant to penicillin in urban Australia ranged from 10.7% in the Australian Capital Territory to 41.8% in New South Wales. In rural and remote Northern Territory penicillin resistance rates remain low (3.0%). In remote Western Australia penicillin resistance rates have increased (5.3%) compared to the previous years, however, there were relatively low numbers of strains available for isolate based testing. To address this and to monitor resistance and inform treatment guidelines, widespread molecular testing for penicillin resistance in Western Australia is in place, and these data are included in the AGSP. The proportion of strains resistant to ciprofloxacin in urban Australia ranged from 16.1% in the Australian Capital Territory to 41% in South Australia. Ciprofloxacin resistance rates remain comparatively low in remote areas of the Northern Territory (3.0%) and remote areas of Western Australia (4.5%).

Resistance profile of Neisseria gonorrhoeae in KwaZulu-Natal, South Africa questioning the effect of the currently advocated dual therapy.

Rambaran S, Naidoo K, Dookie N, Moodley P, Sturm AW. 

Sex Transm Dis. 2018 Dec 5. doi: 10.1097/OLQ.0000000000000961. 



We report on the antimicrobial resistance profile of N.gonorrhoeae isolates and the distribution of tetM genes in isolates with high-level tetracycline resistance in KwaZulu-Natal, South Africa.


Male and female patients presenting with urethral and/or vaginal discharge were recruited into the study. Urethral and cervical secretions were cultured on New York City agar. Confirmatory tests for N.gonorrhoeae included Gram stain, catalase, oxidase and carbohydrate utilization tests. Beta-lactamase was tested by means of the chromogenic cephalosporin test. Minimum inhibitory concentrations (MIC) were determined using agar dilution with multipoint inoculation. Polymerase Chain Reaction (PCR) with gel electrophoresis was used to detect the presence and type of the tetM gene.


N.gonorrhoeae was isolated from the specimens of 319 (26%) of the 1220 recruited patients. Of these 319 isolates 71 % were resistant to 3 or more drugs. Resistance to azithromycin were found in 68% of the isolates. All isolates showed high level tetracycline resistance with MIC values of 16 and 32 mg/ml. The tetM gene was present in 293 (92%). The American type was found in 264 (90%) and the Dutch type in 29 (10 %). Twenty six (8 %) did not carry a tetM gene.


The current syndromic management with dual ceftriaxone and azithromycin is due to the high level of azithromycin resistance factually single drug therapy. High level tetracycline resistance based on a resistance mechanism other than ribosome protection by the tetM gene product is present in N.gonorrhoeae infecting South African patients.

Antibiotic resistance and NG-MAST sequence types of Neisseria gonorrhoeae isolates in Poland compared to the world.

Mlynarczyk-Bonikowska B, Malejczyk M, Majewski S, Unemo M. 

Postepy Dermatol Alergol. 2018 Dec;35(6):346-551. doi: 10.5114/ada.2018.79780.


Gonorrhoea is one of the most common sexually transmitted infections and in 2012, the World Health Organization estimated about 78 million of new global urogenital cases among adults per year. The main concern during the latest decade has been the emergence and spread of multidrug-resistant strains of Neisseria gonorrhoeae. Resistance has emerged internationally to the extended-spectrum cephalosporins, ceftriaxone and cefixime, which are the last remaining options for empiric first-line monotherapy of gonorrhoea. In Poland, the levels of resistance to ciprofloxacin, benzylpenicillin and tetracycline are high, and the prevalence of azithromycin resistance has increased. However, no resistance to ceftriaxone has been identified. The currently spread multidrug-resistant strains frequently represent epidemic clones. The present paper reviews and describes the antimicrobial resistance and N. gonorrhoeae multiantigen sequence typing (NG-MAST) sequence types of N. gonorrhoeae strains spreading in Poland compared to the world.

Molecular Antimicrobial Resistance of Neisseria gonorrhoeae in a Moroccan Area.

Karim S, Bouchikhi C, Banani A, El Fatemi H, Souho T, Erraghay S, Bennani B. (Full Text)

Infect Dis Obstet Gynecol. 2018 Nov 21;2018:7263849. doi: 10.1155/2018/7263849. 



To identify the prevalence and the types of Neisseria gonorrhoeae (NG) resistance plasmids-mediated penicillin (PPNG) and tetracycline (TRNG), the ciprofloxacin resistance (CRNG), and related risk factors of each types of resistance.


The beta-lactamase-producing plasmid types (Africa, Asia, and Toronto), tetM tetracycline resistance plasmid types (America and Dutch), and the determination of the Ser-91 mutation of GyrA were detected by specifics PCRs on 149 diagnosed NG positives samples followed by Hinf1 digestion for tetM and gyrA mutation.


135 (90.1%) samples showed a profile of molecular resistance to at least one antibiotic with predominance of ciprofloxacin resistance. In fact, 36 (24.2%) and 69 (46.3%) cases harbored PPNG and TRNG, respectively, and 116 (77.9%) cases showed the mutation Ser-91 of GyrA (CRNG). From a total of 36 PPNG isolates, the Toronto, Asian, and Toronto/Asian types were detected in 13 (36.1%), 10 (27.8%), and 13 (36.1%) cases, respectively, whereas the African type was not detected. In addition, the American type of TRNG was detected in 92.8% (64/69) of cases, while the Dutch type was detected in 7.2% (5/69) of cases. The association of demographics and clinical variables with NG resistance to ciprofloxacin, penicillin, and tetracycline was studied and the risk factors have been determined.


Resistance to penicillin, tetracycline, and ciprofloxacin among NG samples positives remained at high levels in Morocco as determined by molecular profile. So, the use of molecular tools for NG antimicrobial resistance detection can help in the management and spread limitation of this infection.

Culture-free genotyping of Neisseria gonorrhoeae revealed distinct strains at different anatomical sites in a quarter of patients, the Netherlands, 2012 to 2016.

van der Veer BM, Wolffs PF, Hoebe CJ, Dukers-Muijrers NH, van Alphen LB. (Full Text)

Euro Surveill. 2018 Dec;23(50). doi: 10.2807/1560-7917.ES.2018.23.50.1800253.



Genotyping of Neisseria gonorrhoeae (NG) is essential for surveillance to monitor NG transmission and dissemination of resistant strains. Current genotyping methods rely on bacterial culture which frequently fails.


Our aim was to develop a culture-free genotyping method that is compatible with the widely used N. gonorrhoeae multi-antigen sequence typing (NG-MAST) database, which facilitates genotyping of NG detected at separate anatomical sites in individual patients.


Specific primers for both PCR targets porB and tbpB were designed and technically validated by assessing the analytical sensitivity, cross-reactivity with 32 non-gonoccocal Neisseria species, and concordance with NG-MAST. Clinical application was assessed on 205 paired samples from concurrent NG infections at different anatomical sites of 98 patients (81 men who have sex with men and 17 women) visiting our sexually transmitted infections clinic.


Typing could be consistently performed on samples with a PCR quantification cycle (Cq) value <35. Furthermore, the method showed no cross-reactivity and was concordant with NG-MAST. Culture-free NG-MAST improved the typing rate from 62% (59/95) for cultured samples to 94% (89/95) compared with culture-dependent NG-MAST. Paired samples of 80 of 98 patients were genotyped, revealing distinct NG strains in separate anatomical sites in 25% (20/80) of the patients.


This NG-specific genotyping method can improve NG surveillance as it facilitates genotyping of non-culturable and extra-genital samples. Furthermore, 25% of patients were infected with multiple NG strains, which is missed in current culture-dependent surveillance. Including non-culturable and concurrent NG infections in surveillance informs actions on dissemination of multidrug-resistant NG strains.

Antimicrobial Consumption and Susceptibility of Neisseria gonorrhoeae: A Global Ecological Analysis.

Kenyon C, Buyze J, Wi T. (Full Text)

Front Med (Lausanne). 2018 Nov 27;5:329. doi: 10.3389/fmed.2018.00329. 


Aims: The reasons why antimicrobial resistance in Neisseria gonorrhoeae has emerged explosively in certain populations but not others are poorly understood. We hypothesized that population level consumption of antimicrobials plays a role. Methods: Using susceptibility data from the World Health Organizations Global Gonococcal Antimicrobial Surveillance Programme and antimicrobial consumption data from the IMS Health MIDAS database we built linear regression models with country-level cephalosporin, macrolide, and fluoroquinolone consumption (standard doses/1,000 population/year) as the explanatory variable and 1-year lagged ceftriaxone, azithromycin, and ciprofloxacin resistance as the outcome variables. These were performed at two time points 2008/2009 and 2013/2014. Results: The association between antimicrobial resistance and consumption at the level of individual countries was positive in all six assessments. In four instances the positive associations were statistically significant (cephalosporins 2008: coefficient 0.0005 [95% confidence interval (CI) 0.0002-0.0007] and 2013: coefficient 0.0003 [95% CI 0.0002-0.0004]; macrolides 2013: coefficient 0.0005 [95% CI 0.00002-0.001]; fluoroquinolones 2013: coefficient 0.02 [95% CI 0.006-0.031]). Conclusions: Differences in population level consumption of particular antimicrobials may play a role in explaining the variations in the emergence of antimicrobial resistance in N. gonorrhoeae.

Stably high azithromycin resistance and decreasing ceftriaxone susceptibility in Neisseria gonorrhoeae in 25 European countries, 2016.

Day MJ, Spiteri G, Jacobsson S, Woodford N, Amato-Gauci AJ, Cole MJ, Unemo M; Euro-GASP network. 

BMC Infect Dis. 2018 Dec 3;18(1):609. doi: 10.1186/s12879-018-3528-4.



The European Gonococcal Antimicrobial Surveillance Programme (Euro-GASP) performs annual sentinel surveillance of Neisseria gonorrhoeae susceptibility to therapeutically relevant antimicrobials across the European Union/European Economic Area (EU/EEA). We present the Euro-GASP results from 2016 (25 countries), linked to patient epidemiological data, and compared with data from previous years.


Agar dilution and minimum inhibitory concentration (MIC) gradient strip methodologies were used to determine the antimicrobial susceptibility (using EUCAST breakpoints) of 2660 N. gonorrhoeae isolates from 25 countries across the EU/EEA. Significance of differences compared with Euro-GASP results in previous years was analysed using Z-tests.


No isolates with resistance to ceftriaxone (MIC > 0.125 mg/L) were detected in 2016 (one in 2015). However, the proportion of isolates with decreased susceptibility to ceftriaxone (MICs from 0.03 mg/L to 0.125 mg/L) increased significantly (p = 0.01) from 2015 to 2016. There were 14 (0.5%) isolates with ceftriaxone MICs 0.125 mg/L (on the resistance breakpoint), of which one isolate was resistant to azithromycin and four showed intermediate susceptibility to azithromycin. Cefixime resistance was detected in 2.1% of isolates in 2016 compared with 1.7% in 2015 (p = 0.26) and azithromycin resistance in 7.5% in 2016 compared with 7.1% in 2015 (p = 0.74). Seven (0.3%) isolates from five countries displayed high-level azithromycin resistance (MIC≥256 mg/L) in 2016 compared with five (0.2%) isolates in 2015. Resistance rate to ciprofloxacin was 46.5% compared with 49.4% in 2015 (p = 0.06). No isolates were resistant to spectinomycin and the MICs of gentamicin remained stable compared with previous years.


Overall AMR rates in gonococci in EU/EEA remained stable from 2015 to 2016. However, the ceftriaxone MIC distribution shifted away from the most susceptible (≤0.016 mg/L) and the proportion of isolates with decreased susceptibility to ceftriaxone increased significantly. This development is of concern as current European gonorrhoea management guideline recommends ceftriaxone 500 mg plus azithromycin 2 g as first-line therapy. With azithromycin resistance at 7.5%, the increasing ceftriaxone MICs might soon threaten the effectiveness of this therapeutic regimen and requires close monitoring.

Novel detection strategies and diagnostics

Antimicrobial resistance prediction and phylogenetic analysis of Neisseria gonorrhoeae isolates using the Oxford Nanopore MinION sequencer.

Golparian D, Donà V, Sánchez-Busó L, Foerster S, Harris S, Endimiani A, Low N, Unemo M. (Full Text)

Sci Rep. 2018 Dec 4;8(1):17596. doi: 10.1038/s41598-018-35750-4.


Antimicrobial resistance (AMR) in Neisseria gonorrhoeae is common, compromising gonorrhoea treatment internationally. Rapid characterisation of AMR strains could ensure appropriate and personalised treatment, and support identification and investigation of gonorrhoea outbreaks in nearly real-time. Whole-genome sequencing is ideal for investigation of emergence and dissemination of AMR determinants, predicting AMR, in the gonococcal population and spread of AMR strains in the human population. The novel, rapid and revolutionary long-read sequencer MinION is a small hand-held device that generates bacterial genomes within one day. However, accuracy of MinION reads has been suboptimal for many objectives and the MinION has not been evaluated for gonococci. In this first MinION study for gonococci, we show that MinION-derived sequences analysed with existing open-access, web-based sequence analysis tools are not sufficiently accurate to identify key gonococcal AMR determinants. Nevertheless, using an in house-developed CLC Genomics Workbench including de novo assembly and optimised BLAST algorithms, we show that 2D ONT-derived sequences can be used for accurate prediction of decreased susceptibility or resistance to recommended antimicrobials in gonococcal isolates. We also show that the 2D ONT-derived sequences are useful for rapid phylogenomic-based molecular epidemiological investigations, and, in hybrid assemblies with Illumina sequences, for producing contiguous assemblies and finished reference genomes.

Genome-wide discovery of epistatic loci affecting antibiotic resistance in Neisseria gonorrhoeae using evolutionary couplings.

Schubert B, Maddamsetti R, Nyman J, Farhat MR, Marks DS. (Full Text)

Nat Microbiol. 2019 Feb;4(2):328-338. doi: 10.1038/s41564-018-0309-1.


Genome analysis should allow the discovery of interdependent loci that together cause antibiotic resistance. In practice, however, the vast number of possible epistatic interactions erodes statistical power. Here, we extend an approach that has been successfully used to identify epistatic residues in proteins to infer genomic loci that are strongly coupled. This approach reduces the number of tests required for an epistatic genome-wide association study of antibiotic resistance and increases the likelihood of identifying causal epistasis. We discovered 38 loci and 240 epistatic pairs that influence the minimum inhibitory concentrations of 5 different antibiotics in 1,102 isolates of Neisseria gonorrhoeae that were confirmed in a second dataset of 495 isolates. Many known resistance-affecting loci were recovered; however, the majority of associations occurred in unreported genes, such as murE. About half of the discovered epistasis involved at least one locus previously associated with antibiotic resistance, including interactions between gyrA and parC. Still, many combinations involved unreported loci and genes. While most variation in minimum inhibitory concentrations could be explained by identified loci, epistasis substantially increased explained phenotypic variance. Our work provides a systematic identification of epistasis affecting antibiotic resistance in N. gonorrhoeae and a generalizable approach for epistatic genome-wide association studies.

Comparison of Neisseria gonorrhoeae minimum inhibitory concentrations obtained using agar dilution versus microbroth dilution methods.

Jacobson RK, Notaro MJ, Carr GJ. (Full Text)

J Microbiol Methods. 2019 Jan 7;157:93-99. doi: 10.1016/j.mimet.2019.01.001.


With increasing antibiotic resistance observed amongst clinical isolates of Neisseria gonorrhoeae, the second most prevalent sexually transmitted bacterial disease in the United States, there is still a need for antimicrobial susceptibility testing (AST). The current method recommended by the Clinical and Laboratory Standards Institute is agar dilution. In this study, we show that a commercially available version of Fastidious Broth is capable of supporting N. gonorrhoeae in the evaluation of minimum inhibitory concentrations of 4 antibiotics (ceftriaxone, azithromycin, ciprofloxacin, and tetracycline), when comparing the agar dilution (AD) versus microbroth dilution (MBD) method and the susceptibilities obtained for 32 N. gonorrhoeae isolates. Herein, 3 out of the 4 antibiotics tested showed 94% or greater essential agreement (EA) and 91% or greater categorical agreement (CA) respectively, when comparing the MBD versus AD methods.

Evaluation of the accuracy of molecular assays targeting the mutation A2059G for detecting high-level azithromycin resistance in Neisseria gonorrhoeae: a systematic review and meta-analysis.

Wang F, Liu J, Liu H, Huang J, Chen S, Chen X, Yin Y. (Full Text)

Infect Drug Resist. 2018 Dec 28;12:95-104. doi: 10.2147/IDR.S183754.



Neisseria gonorrhoeae resistance to azithromycin has become a significant public health concern globally, and high-level azithromycin-resistant (HL-AzmR) isolates have emerged frequently. However, high-level azithromycin resistance is considered to be caused by mutated alleles of 23S rRNA gene at position 2059, and identification of HL-AzmR isolates mainly relies on agar dilution method or E-test method. This study aimed to assess the accuracy of the molecular assays targeting the mutation A2059G for identifying HL-AzmR isolates and thereby determine the association between the mutation and high-level azithromycin resistance.


Two researchers independently searched six databases to identify studies published from the launch of each database to October 15, 2017. The fixed effects model was used to estimate the pooled sensitivity rate, specificity rate, positive predictive value (PPV), and negative predictive value (NPV). Summary receiver operating characteristic curves were generated, and the area under the curve (AUC) was determined to estimate the overall performance of the assays. The Deeks' test was conducted to evaluate potential publication bias.


Ten relevant studies were included in the meta-analysis to assess the synthetic accuracy of the molecular assays. The molecular assays had the synthetic sensitivity rate of 97.8% and the synthetic specificity rate of 99.1%. And the aggregated PPV and NPV were 96.4% and 99.5%, respectively. AUC was 0.99, suggesting a close relation existing between the mutation A2059G and high-level azithromycin resistance. This indicated that the molecular assays targeting the mutation A2059G have relatively high overall accuracy for identifying HL-AzmR N. gonor-rhoeae isolates. Publication bias was statistically significant.


The mutation A2059G is the critical factor causing high-level azithromycin resistance. Hence, molecular methods are recommended to be put into clinical practice by commercialization, which will assist clinicians to prescribe more precisely.

Novel antibiotics, mechanisms, vaccine, and other advances

Pharmacokinetic Data Are Predictive of in vivo Efficacy for Cefixime and Ceftriaxone against Susceptible and Resistant Neisseria gonorrhoeae Strains in the Gonorrhea Mouse Model.

Connolly KL, Eakin AE, Gomez C, Osborn BL, Unemo M, Jerse AE.

Antimicrob Agents Chemother. 2019 Jan 14. pii: AAC.01644-18. doi: 10.1128/AAC.01644-18.


There is a pressing need for drug development for gonorrhea. Here we describe pharmacokinetics/pharmacodynamics (PK/PD) analysis of extended-spectrum cephalosporins (ESC) against drug-susceptible and drug-resistant gonococcal strains in a murine genital tract infection model. PK determined in uninfected mice displayed a clear dose response in plasma levels following single doses of ceftriaxone (CRO) (intraperitoneal) or cefixime (CFM) (oral). The observed doses required for efficacy against ESCS strain FA1090 were 5 mg/kg (CRO) and 12 mg/kg (CFM); these doses had estimated therapeutic times (time of free drug above the MIC, fTMIC) of 24 h and 37 h, respectively. No single dose of CRO or CFM was effective against the ESCR strain H041. However, fractionation (TIDq8h) of a 120 mg/kg dose of CRO resulted in estimated therapeutic times in the range of 23 h and cleared H041 infection in a majority (90%) of mice, comparable to gentamicin. In contrast, multiple CFM doses of 120 or 300 mg/kg administered TIDq8h cleared infection in ≤ 50% of mice with therapeutic times estimated from single-dose PK data, of 13 and 27 h, respectively. This study reveals a clear relationship between plasma ESC levels and bacterial clearance rates in the gonorrhea mouse model. The PK/PD relationships in mice reflected that observed in humans with in vivo efficacy against an ESCS strain requiring doses that yielded an fTMIC in excess of 20-24 h. PK data also accurately predicted the failure of single doses of ESCs against an ESCR strain and were useful in designing effective dosing regimens.


Macrophage-Neisseria gonorrhoeae Interactions: A Better Understanding of Pathogen Mechanisms of Immunomodulation.

Escobar A, Rodas PI, Acuña-Castillo C.  (Full Text)

Front Immunol. 2018 Dec 21;9:3044. doi: 10.3389/fimmu.2018.03044. eCollection 2018.


Neisseria gonorrhoeae is a significant health problem worldwide due to multi-drug resistance issues and absence of an effective vaccine. Patients infected with N. gonorrhoeae have not shown a better immune response in successive infections. This might be explained by the fact that N. gonorrhoeae possesses several mechanisms to evade the innate and adaptative immune responses at different levels. Macrophages are a key cellular component in the innate immune response against microorganisms. The current information suggests that gonococcus can hijack the host response by mechanisms that involve the control of macrophages activity. In this mini review, we intend to condense the recent knowledge on the macrophage-N. gonorrhoeae interactions with a focus on strategies developed by gonococcus to evade or to exploit immune response to establish a successful infection. Finally, we discuss the opportunities and challenges of therapeutics for controlling immune manipulation by N. gonorrhoeae.

Photo-inactivation of Neisseria gonorrhoeae: A paradigm changing approach for combating antibiotic-resistant gonococcal infection.

Wang Y, Ferrer-Espada R, Baglo, Goh XS, Held KD, Grad YH, Gu Y, Gelfand JA, Dai T. 

J Infect Dis. 2019 Jan 9. doi: 10.1093/infdis/jiz018.


Antimicrobial resistance in Neisseria gonorrhoeae is a major issue of public health, and there is a critical need for the development of new anti-gonococcal strategies. In this study, we investigated the effectiveness of antimicrobial blue light (aBL; 405 nm wavelength), an innovative non-pharmacological approach, for the inactivation of N. gonorrhoeae. Our findings indicated that aBL preferentially inactivated N. gonorrhoeae, including antibiotic-resistant strains, over human vaginal epithelial cells in vitro. Furthermore, no genotoxicity of aBL to the vaginal epithelial cells was observed at the radiant exposure for inactivating N. gonorrhoeae. aBL also effectively inactivated N. gonorrhoeae that had attached to and invaded into the vaginal epithelial cells in their co-cultures. No gonococcal resistance to aBL developed after 15 successive cycles of sub-therapeutic aBL inactivation. Endogenous aBL-activatable photosensitizing porphyrins in N. gonorrhoeae were identified and quantified using ultra-performance liquid chromatography, with coproporphyrin being the most abundant species in all the N. gonorrhoeae strains studied. Singlet oxygen was involved in aBL inactivation of N. gonorrhoeae. Taken together, aBL represents a potent potential treatment for antibiotic-resistant gonococcal infection.

Pharmacokinetic considerations regarding the treatment of bacterial sexually transmitted infections with azithromycin: a review

Fabian Yuh Shiong Kong  Patrick Horner  Magnus Unemo  Jane S Hocking. 

Journal of Antimicrobial Chemotherapy, dky548,


Rates of bacterial sexually transmitted infections (STIs) continue to rise, demanding treatments to be highly effective. However, curing infections faces significant challenges due to antimicrobial resistance in Neisseria gonorrhoeae and Mycoplasma genitalium and especially treating STIs at extragenital sites, particularly rectal chlamydia and oropharyngeal gonorrhoea. As no new antimicrobials are entering the market, clinicians must optimize the currently available treatments, but robust data are lacking on how the properties or pharmacokinetics of antimicrobials can be used to inform STI treatment regimens to improve treatment outcomes. This paper provides a detailed overview of the published pharmacokinetics of antimicrobials used to treat STIs and how factors related to the drug (tissue distribution, protein binding and t½), human (pH, inflammation, site of infection, drug side effects and sexual practices) and organism (organism load and antimicrobial resistance) can affect treatment outcomes. As azithromycin is commonly used to treat chlamydia, gonorrhoea and M. genitalium infections, and its pharmacokinetics are well studied, it is the main focus of this review. Suggestions are also provided on possible dosing regimens when using extended and/or higher doses of azithromycin, which appropriately balance efficacy and side effects. The paper also emphasizes the limitations of currently published pharmacokinetic studies including oropharyngeal gonococcal infections, where very limited data exist around ceftriaxone pharmacokinetics and its use in combination with azithromycin. In future, the different anatomical sites of infections may require alternative therapeutic approaches.

Evaluation of apramycin against spectinomycin-resistant and -susceptible strains of Neisseria gonorrhoeae.

Riedel S, Vijayakumar D, Berg G, Kang AD, Smith KP, Kirby JE. 

J Antimicrob Chemother. 2019 Jan 27. doi: 10.1093/jac/dkz012. 



The emergence of Neisseria gonorrhoeae resistant to all currently available antimicrobial therapies poses a dire public health threat. New antimicrobial agents with activity against N. gonorrhoeae are urgently needed. Apramycin is an aminocyclitol aminoglycoside with broad-spectrum in vitro activity against MDR Gram-negative pathogens and Staphylococcus aureus. However, its activity against N. gonorrhoeae has not been described.


The activity spectrum of apramycin against a collection of MDR N. gonorrhoeae was assessed. Isolates tested included those susceptible and resistant to the structurally distinct aminocyclitol, spectinomycin.


The modal MICs for apramycin and spectinomycin were 16 mg/L and 32 mg/L, respectively. The epidemiological cut-off (ECOFF) for apramycin was 64 mg/L. No strains among 77 tested had an MIC above this ECOFF, suggesting very low levels of acquired apramycin resistance. In time-kill analysis, apramycin demonstrated rapid bactericidal activity comparable to that of spectinomycin.


Apramycin has broad-spectrum, rapidly bactericidal activity against N. gonorrhoeae. Future pharmacokinetic and pharmacodynamic studies will be needed to determine whether apramycin and/or apramycin derivatives hold promise as new therapeutics for N. gonorrhoeae infection.

Evaluation of Susceptibilities to Carbapenems and Faropenem Against Cephalosporin-Resistant Neisseria gonorrhoeae Clinical Isolates with penA Mosaic Alleles.

Hiyama Y, Takahashi S, Sato T, Shinagawa M, Fukushima Y, Nakajima C, Suzuki Y, Masumori N, Yokota SI. (Full Text)

Microb Drug Resist. 2019 Jan 24. doi: 10.1089/mdr.2018.0263.


Neisseria gonorrhoeae is a principal pathogen for sexually transmitted infections, especially for male urethritis. Currently, the prevalence of multidrug resistance is increasing. Carbapenems are broad-spectrum antimicrobials that are widely used in the clinical setting, especially for multidrug-resistant Gram-negative bacteria. However, susceptibility to carbapenems has not been well evaluated for cephalosporin-resistant N. gonorrhoeae isolates. In this study, we determined the susceptibility to a series of carbapenems (meropenem, imipenem, doripenem, and biapenem) and faropenem against cephalosporin-resistant (resistant to cefixime, but susceptible to ceftriaxone) and cephalosporin-susceptible N. gonorrhoeae clinical isolates. The gene mutations associated with β-lactam resistance were evaluated. All cephalosporin-resistant N. gonorrhoeae isolates possessed mosaic mutation alleles in penA (NG-STAR penA-10.001, 27.001, or 108.001). They exhibited a low minimum inhibitory concentration (MIC) (≤0.125 mg/L) for meropenem and markedly high MICs (0.5-2 mg/L) for other carbapenems and faropenem. The strongest association was observed between the mosaic alleles in penA and decreased susceptibility to carbapenems and faropenem compared with mutations in mtrR, porB, and ponA. These results suggest that meropenem may serve as an alternative therapeutic agent for cephalosporin-resistant N. gonorrhoeae with a mosaic allele in penA, whereas other carbapenems and faropenem may be ineffective.


In vitro activity of EDTA and TOL-463 against Neisseria gonorrhoeae.

Nash EE, Henning TC, Pham CD, Pettus K, Sharpe S, Kersh EN. (Full Text)

Diagn Microbiol Infect Dis. 2018 Nov 10. pii: S0732-8893(18)30603-5. doi: 10.1016/j.diagmicrobio.2018.10.021.


Neisseria gonorrhoeae quickly develops drug resistance. Time-kill curves revealed that EDTA and TOL-463 inhibit growth similar to penicillin, ciprofloxacin, and azithromycin. Furthermore, synergistic and additive antimicrobial interactions occurred when EDTA and TOL-463 were combined with penicillin or azithromycin, respectively, suggesting that further investigations into these unconventional antimicrobials may be advantageous.


The serogroup B meningococcal vaccine Bexsero elicits antibodies to Neisseria gonorrhoeae.

Semchenko EA, Tan A, Borrow R, Seib KL. (Full Text)

Clin Infect Dis. 2018 Dec 14. doi: 10.1093/cid/ciy1061.



Neisseria gonorrhoeae and Neisseria meningitidis are closely related bacteria that cause a significant global burden of disease. Control of gonorrhoea is becoming increasingly difficult due to widespread antibiotic resistance. While vaccines are routinely used for N.meningitidis, no vaccine is available for N.gonorrhoeae. Recently, the outer membrane vesicle (OMV) meningococcal B vaccine, MeNZB, was reported to be associated with reduced rates of gonorrhoea following a mass vaccination campaign in New Zealand. To probe the basis for this protection we assessed cross reactivity to N. gonorrhoeae of serum raised to the meningococcal vaccine Bexsero, which contains the MeNZB OMV component plus three recombinant antigens (NadA, fHBP-GNA2091, and NHBA-GNA1030).


Bioinformatic analysis was performed to assess the similarity of MeNZB OMV and Bexsero antigens to gonococcal proteins. Rabbits were immunised with the OMV component or the three recombinant antigens of Bexsero, and Western blot and ELISA were used to assess generation of antibodies recognising N.gonorrhoeae. Serum from humans immunised with Bexsero was investigated assess the nature of the anti-gonococcal response.


There is a high level of sequence identity between MeNZB OMV and Bexsero OMV antigens, and gonococcal proteins. NHBA is the only Bexsero recombinant antigen that is conserved and surfaced exposed in N.gonorrhoeae. Bexsero induces antibodies in humans that recognise gonococcal proteins.


The anti-gonococcal antibodies induced by MeNZB-like OMV proteins could explain the previously seen decrease in gonococcal cases following MeNZB vaccination. The high level of anti-gonococcal-NHBA antibodies generated by Bexsero vaccination in humans may result in additional cross-protection against gonorrhoea.


Prediction of epitopes of Neisseria Gonorrhoeae against USA human leukocyte antigen background: An immunoinformatic approach towards development of future vaccines for USA population.

Mahmood MS, Asad-Ullah M, Batool H, Batool S, Ashraf NM. 

Mol Cell Probes. 2019 Feb;43:40-44. doi: 10.1016/j.mcp.2018.11.007. 


Gonorrheal infections are the second most prevalent sexually transmitted diseases STDs in the USA populations after Chlamydia. These infections have now become an urgent problem to address because Neisseria gonorrhoeae is capable of developing resistance to multiple antibiotic classes. Infection with these antibiotic-resistant strains has become the major public health concern. Although extensive researches are ongoing to control its transmission and to develop the productive treatments against this pathogen, no effective vaccine could develop till now. The present study will effectively contribute to the future designing of USA specific epitope-based vaccines. Through computational approaches, this study has highlighted putative epitopes from Neisseria gonorrhoeae which restrict maximally to the frequent HLA alleles in the USA populations. Antigenic and non-allergenic nature of predicted epitopes was verified using vexijen and AllerTOP tools respectively. Total seven epitopes, four from class-I and three from class-II were antigenic as well as non-allergenic. These epitopes showed USA population coverage of 99.3% with no allergenic response. Still, additional studies are needed to validate the immunogenic properties of the predicted epitopes which are likely vaccine target for gonorrhoea in the USA populations.


The MtrCDE Efflux Pump Contributes to Survival of Neisseria gonorrhoeae From Human Neutrophils and Their Antimicrobial Components.

Handing JW, Ragland SA, Bharathan UV, Criss AK.

Front Microbiol. 2018 Nov 20;9:2688. doi: 10.3389/fmicb.2018.02688.


The mucosal inflammatory response to Neisseria gonorrhoeae (Gc) is characterized by recruitment of neutrophils to the site of infection. Gc survives exposure to neutrophils by limiting the ability of neutrophils to make antimicrobial products and by expressing factors that defend against these products. The multiple transferable resistance (Mtr) system is a tripartite efflux pump, comprised of the inner membrane MtrD, the periplasmic attachment protein MtrC, and the outer membrane channel MtrE. Gc MtrCDE exports a diverse array of substrates, including certain detergents, dyes, antibiotics, and host-derived antimicrobial peptides. Here we report that MtrCDE contributes to the survival of Gc after exposure to adherent, chemokine-treated primary human neutrophils, specifically in the extracellular milieu. MtrCDE enhanced survival of Gc in neutrophil extracellular traps and in the supernatant from neutrophils that had undergone degranulation (granule exocytosis), a process that releases antimicrobial proteins into the extracellular milieu. The extent of degranulation was unaltered in neutrophils exposed to parental or mtr mutant Gc. MtrCDE expression contributed to Gc defense against some neutrophil-derived antimicrobial peptides but not others. These findings demonstrate that the Mtr system contributes to Gc survival after neutrophil challenge, a key feature of the host immune response to acute gonorrhea.


Neisseria gonorrhoeae PBP3 and PBP4 Facilitate NOD1 Agonist Peptidoglycan Fragment Release and Survival in Stationary Phase.

Schaub RE, Perez-Medina KM, Hackett KT, Garcia DL, Dillard JP.

Infect Immun. 2019 Jan 24;87(2). pii: e00833-18. doi: 10.1128/IAI.00833-18.


Neisseria gonorrhoeae releases peptidoglycan fragments during growth, and these molecules induce an inflammatory response in the human host. The proinflammatory molecules include peptidoglycan monomers, peptidoglycan dimers, and free peptides. These molecules can be released by the actions of lytic transglycosylases or an amidase. However, >40% of the gonococcal cell wall is cross-linked, where the peptide stem on one peptidoglycan strand is linked to the peptide stem on a neighboring strand, suggesting that endopeptidases may be required for the release of many peptidoglycan fragments. Therefore, we characterized mutants with individual or combined mutations in genes for the low-molecular-mass penicillin-binding proteins PBP3 and PBP4. Mutations in either dacB, encoding PBP3, or pbpG, encoding PBP4, did not significantly reduce the release of peptidoglycan monomers or free peptides. A mutation in dacB caused the appearance of a larger-sized peptidoglycan monomer, the pentapeptide monomer, and an increased release of peptidoglycan dimers, suggesting the involvement of this enzyme in both the removal of C-terminal d-Ala residues from stem peptides and the cleavage of cross-linked peptidoglycan. Mutation of both dacB and pbpG eliminated the release of tripeptide-containing peptidoglycan fragments concomitantly with the appearance of pentapeptide and dipeptide peptidoglycan fragments and higher-molecular-weight peptidoglycan dimers. In accord with the loss of tripeptide peptidoglycan fragments, the level of human NOD1 activation by the dacB pbpG mutants was significantly lower than that by the wild type. We conclude that PBP3 and PBP4 overlap in function for cross-link cleavage and that these endopeptidases act in the normal release of peptidoglycan fragments during growth.