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

Neisseria gonorrhoeae antimicrobial resistance (AMR) monthly UPDATES

September, 2019

Epidemiology and Surveillance

World Health Organization Global Gonococcal Antimicrobial Surveillance Program (WHO GASP): review of new data and evidence to inform international collaborative actions and research efforts.

Unemo M, Lahra MM, Cole M, Galarza P, Ndowa F, Martin I, Dillon JR, Ramon-Pardo P, Bolan G, Wi T. (Full Text)

Sex Health. 2019 Aug 23. doi: 10.1071/SH19023. [Epub ahead of print]


Antimicrobial resistance (AMR) in Neisseria gonorrhoeae is a serious public health problem, compromising the management and control of gonorrhoea globally. Resistance in N. gonorrhoeae to ceftriaxone, the last option for first-line empirical monotherapy of gonorrhoea, has been reported from many countries globally, and sporadic failures to cure especially pharyngeal gonorrhoea with ceftriaxone monotherapy and dual antimicrobial therapies (ceftriaxone plus azithromycin or doxycycline) have been confirmed in several countries. In 2018, the first gonococcal isolates with ceftriaxone resistance plus high-level azithromycin resistance were identified in England and Australia. The World Health Organization (WHO) Global Gonococcal Antimicrobial Surveillance Program (GASP) is essential to monitor AMR trends, identify emerging AMR and provide evidence for refinements of treatment guidelines and public health policy globally. Herein we describe the WHO GASP data from 67 countries in 2015-16, confirmed gonorrhoea treatment failures with ceftriaxone with or without azithromycin or doxycycline, and international collaborative actions and research efforts essential for the effective management and control of gonorrhoea. In most countries, resistance to ciprofloxacin is exceedingly high, azithromycin resistance is present and decreased susceptibility or resistance to ceftriaxone has emerged. Enhanced global collaborative actions are crucial for the control of gonorrhoea, including improved prevention, early diagnosis, treatment of index patient and partner (including test-of-cure), improved and expanded AMR surveillance (including surveillance of antimicrobial use and treatment failures), increased knowledge of correct antimicrobial use and the pharmacokinetics and pharmacodynamics of antimicrobials and effective drug regulations and prescription policies (including antimicrobial stewardship). Ultimately, rapid, accurate and affordable point-of-care diagnostic tests (ideally also predicting AMR and/or susceptibility), new therapeutic antimicrobials and, the only sustainable solution, gonococcal vaccine(s) are imperative.

Gentamicin susceptibility of Neisseria gonorrhoeae isolates from 7 provinces in China.

Liu JW, Xu WQ, Zhu XY, Dai XQ, Chen SC, Han Y, Liu J, Chen XS, Yin YP. (Full Text)

Infect Drug Resist. 2019 Aug 9;12:2471-2476. doi: 10.2147/IDR.S214059. eCollection 2019.



Gentamicin is a promising antimicrobial for the treatment of gonorrhea. The study aimed to evaluate gentamicin minimum inhibitory concentrations (MICs) of Neisseria gonorrhoeae isolates in China.


In this study, the agar dilution method was used to determine the MICs of 470 isolates collected in 2016 to four effective antimicrobials (gentamicin, azithromycin, ceftriaxone, and spectinomycin).


Gentamicin MICs ranged from 1 to 8 mg/L. No isolate was resistant to gentamicin. Of seven isolates simultaneously resistant to azithromycin and ceftriaxone, 6 isolates demonstrated MICs of 4 mg/L or less to gentamicin. No cross relationships were found between MICs of gentamicinand susceptibility profiles of azithromycin, ceftriaxone, and spectinomycin.


The in vitro results suggest that gentamicin can be a promising treatment option for gonococcal infections in China. Clinical trials to evaluate the therapeutic efficacy of gentamicin are required.

Changing of antibiotic susceptibility and molecular characterization of Neisseria gonorrhoeae isolates in Guangdong, China:in a background of rapidly raising epidemic.

Qin X, Zhao Y, Chen W, Wu X, Tang S, Li G, Yuqi Y, Cao W, Liu X, Huang J, Yang J, Chen W, Tang W, Zheng H.

Int J Antimicrob Agents. 2019 Aug 16. pii: S0924-8579(19)30226-2. doi: 10.1016/j.ijantimicag.2019.08.015. [Epub ahead of print]



The global prevalence of Neisseria gonorrhoeae infections has rapidly increased since 2015 in China. Antibiotic resistance and molecular mobilization of N.gonorrhoeae are two important factors that drive the increasing prevalence of N.gonorrhoeae infections. This study aimed to explore the changes in antibiotic susceptibility and molecular characteristics of N.gonorrhoeae isolates collected in Guangdong, China over the period of 2013 to 2017.


A total of 704 isolates were collected in two cities in Guangdong, China over the period of 2013 to 2017. The minimum inhibitory concentrations (MICs) of major antimicrobials against the isolates were quantified through the agar dilution method. The plasmid types of Penicillinase-producing N.gonorrhoeae (PPNG) and Tetracycline-Resistant N.gonorrhoeae (TRNG) were characterized. The collected isolates were genotyped through N.gonorrhoeae multiantigen sequence typing (NG-MAST). All statistical analyses were performed using SPSS 20.0 (IBM) software.


High resistance to penicillin (68.2%), tetracycline (85.7 %) and ciprofloxacin (98.2 %) were observed during the study period, Spectinomycin, ceftriaxone and azithromycin appeared to be effective agents with sensitive rates of 100%, 96.4 % and 90.7%, respectively. The penicillin resistance rates decreased from 78.4% (80/102) to 73.6% (120/163) (P = 0.001). The azithromycin resistance rates decreased from 9.8% (10/102) to 3.7% (6/163) (P = 0.004). The total prevalence of PPNG, TRNG, and PPNG/TRNG were 25.4%, 33.1%, and 13.4%, respectively. The PPNG rate decreased from 37.3% (38/102) to 23.9% (39/163) (P = 0.002), TRNG from 50.0% (51/102) to 31.3% (51/163) (P = 0.004), and PPNG/TRNG from 23.5% (24/102) to 11.7% (19/163) (P = 0.017). However, the ratio of African-type PPNG increased from 18.4%(7/38) to 64.1% (25/39) (P < 0.001) instead of decreasing Asian-type PPNG from 81.6% (31/38) to 33.3% (13/39) (P < 0.001), and the ratio of American-type TRNG increased 0%(0/51) to 13.7% (P = 0.003) instead of decreasing the Dutch-type TRNG from 100%(51/51) to 86.3% (P = 0.003). A total of 271 sequence types (STs) were identified by NG-MAST from the 380 isolates collected in 2013, 2014, and 2017, 145 (38.1%) novel STs were genotyped for the first time. The most prevalent STs were ST5308 (n = 10), ST5061 (n = 7), and ST3741 (n = 6). All ST4676 isolates (n = 4) exhibited decreased susceptibility to ceftriaxone (MIC ≥ 0.125).


The resistance to penicillin, tetracycline, and ciprofloxacin continue to be high. The African-type PPNG is increasing and replacing Asian-type PPNG, and more novel STs strains have emerged. The gonococcal isolates with new genotypes might contribute to the raising epidemic of gonorrhea in this area.

Ceftriaxone Reduced Susceptible Neisseria gonorrhoeae in the Netherlands, 2009 to 2017: From PenA Mosaicism to A501T/V Nonmosaicism.

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 Sep;46(9):594-601. doi: 10.1097/OLQ.0000000000001031.



To compare molecular and epidemiological differences between ceftriaxone-reduced susceptible (CRO-RS) and ceftriaxone-susceptible (CRO-S) N. 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 to 2017. Ng multiantigen sequence typing (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 were produced based on multilocus variable number of tandem repeats analysis for Ng (NG-MLVA) genotypes.


We selected 174 CRO-RS isolates (minimum inhibitory concentration, ≥0.064 mg/L) and 174 CRO-S isolates (minimum inhibitory concentration, ≤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 (odds ratios [OR], 3.64; P < 0.001), and patients with CRO-RS Ng were less often human immunodeficiency virus (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 to 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 to 2015 (n = 24; 82.7%), had a nonmosaic 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 to 2017 (n = 26; 70.2%), had a nonmosaic 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 toward nonmosaic 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.

Emerging international strain of multidrug-resistant Neisseria gonorrhoeae: Infection in a man with urethral discharge.

Smyczek P, Chu A, Berenger B. (Full Text)

Can Fam Physician. 2019 Aug;65(8):552-554.

Temporal evolution of antimicrobial resistance among Neisseria gonorrhoeae clinical isolates in the most populated South American Metropolitan Region.

Martins RA, Cassu-Corsi D, Nodari CS, Cayô R, Natsumeda L, Streling AP, Doi AM, da Silva RJC, Bocalon RAL, Gales AC, Pignatari ACC. 

Mem Inst Oswaldo Cruz. 2019;114:e190079. doi: 10.1590/0074-02760190079. Epub 2019 Aug 12. (Full Text)


A total of 124 Neisseria gonorrhoeae isolates recovered during a 12-year period (2003-2015) from outpatients assisted at Centro de Referência e Treinamento DST/AIDS-CRT of São Paulo city, Brazil, were analysed. The following resistance rates were observed: penicillin-59.6%, ciprofloxacin-15.3%, and azithromycin-6.7%. Although reduced susceptibility to these drugs was observed since 2003, no ceftriaxone-resistant isolates were detected. Ciprofloxacin- and azithromycin non-susceptible isolates were grouped in 11 clusters. Mutations were detected in GyrA and ParC of isolates 124 and 260, and a C2611T substitution on 23S rRNA alleles was also observed in isolate 260. Both isolates belonged to ST1901/ST6210 (MSLT/NG-MAST schemes).

Genetic Characterization and Enhanced Surveillance of Ceftriaxone-Resistant Neisseria gonorrhoeae Strain, Alberta, Canada, 2018.

Berenger BM, Demczuk W, Gratrix J, Pabbaraju K, Smyczek P, Martin I. 

Emerg Infect Dis. 2019 Sep;25(9):1660-1667. doi: 10.3201/eid2509.190407. Epub 2019 Sep 17. (Full Text)


In July 2018, a case of Neisseria gonorrhoeae associated with ceftriaxone treatment failure was identified in Alberta, Canada. We identified the isolate and nucleic acid amplification testing (NAAT) specimen as the ceftriaxone-resistant strain multilocus sequence type 1903/NG-MAST 3435/NG-STAR 233, originally identified in Japan (FC428), with the same penA 60.001 mosaic allele and genetic resistance determinants. Core single-nucleotide variant (SNV) analysis identified 13 SNVs between this isolate and FC428. Culture-independent surveillance by PCR for the A311V mutation in the penA allele and N. gonorrhoeae multiantigen sequence typing directly from NAAT transport media positive for N. gonorrhoeae by NAAT did not detect spread of the strain. We identified multiple sequence types not previously detected in Alberta by routine surveillance. This case demonstrates the benefit of using culture-independent methods to enhance detection, public health investigations, and surveillance to address this global threat.

Trends and risk factors for antimicrobial-resistant Neisseria gonorrhoeae, Melbourne, Australia, 2007 - 2018.

Williamson DA, Fairley CK, Howden BP, Chen MY, Stevens K4, De Petra V, Denham I, Chow EPF.

Antimicrob Agents Chemother. 2019 Aug 5. pii: AAC.01221-19. doi: 10.1128/AAC.01221-19. [Epub ahead of print]. (Full Text)


Antimicrobial resistance (AMR) in Neisseria gonorrhoeae is a major public health problem. Traditionally, AMR surveillance programs for N. gonorrhoeae have focused mainly on laboratory data to describe the prevalence and trends of resistance. However, integrating individual-level risk factors (e.g. sexual orientation or international travel) with laboratory data provides important insights into factors promoting the spread of resistant N. gonorrhoeae Here, over a twelve-year period, we assessed the trends and risk factors for resistant N. gonorrhoeae in individuals attending a large publicly-funded sexual health centre in Melbourne, Australia. A total of 7,588 N. gonorrhoeae isolates were cultured from 5,593 individuals between January 1st, 2007 and December 31st, 2018. The proportion of isolates with penicillin resistance decreased from 49.5% in 2007 to 18.3% in 2018 (ptrend<0.001), and from 63.5% in 2007 to 21.1% in 2018 for ciprofloxacin resistance (ptrend<0.001). In contrast, the proportion of isolates displaying decreased susceptibility to ceftriaxone increased from 0.5% in 2007 to 2.9% in 2018 (ptrend<0.001), with a significant increase in low-level azithromycin resistance, from 2.5% in 2012 to 8.2% in 2018 (ptrend<0.001). Multivariate analysis identified risk factors for multidrug-resistant (MDR) N. gonorrhoeae, namely female sex and country of birth, with MDR isolates more common in individuals born in north-east Asia, further highlighting the importance of this region and international travel as factors in the cross-border transmission of MDR N. gonorrhoeae Future surveillance work should incorporate additional epidemiological and genomic data to provide a comprehensive overview of the emergence and spread of resistant N. gonorrhoeae.


Novel detection strategies and diagnostics

Evaluation of parameters affecting performance and reliability of machine learning-based antibiotic susceptibility testing from whole genome sequencing data.

Hicks AL, Wheeler N, Sánchez-Busó L, Rakeman JL, Harris SR, Grad YH. 

PLoS Comput Biol. 2019 Sep 3;15(9):e1007349. doi: 10.1371/journal.pcbi.1007349. [Epub ahead of print]


Prediction of antibiotic resistance phenotypes from whole genome sequencing data by machine learning methods has been proposed as a promising platform for the development of sequence-based diagnostics. However, there has been no systematic evaluation of factors that may influence performance of such models, how they might apply to and vary across clinical populations, and what the implications might be in the clinical setting. Here, we performed a meta-analysis of seven large Neisseria gonorrhoeae datasets, as well as Klebsiella pneumoniae and Acinetobacter baumannii datasets, with whole genome sequence data and antibiotic susceptibility phenotypes using set covering machine classification, random forest classification, and random forest regression models to predict resistance phenotypes from genotype. We demonstrate how model performance varies by drug, dataset, resistance metric, and species, reflecting the complexities of generating clinically relevant conclusions from machine learning-derived models. Our findings underscore the importance of incorporating relevant biological and epidemiological knowledge into model design and assessment and suggest that doing so can inform tailored modeling for individual drugs, pathogens, and clinical populations. We further suggest that continued comprehensive sampling and incorporation of up-to-date whole genome sequence data, resistance phenotypes, and treatment outcome data into model training will be crucial to the clinical utility and sustainability of machine learning-based molecular diagnostics.

Agent-based modelling study of antimicrobial-resistant Neisseria gonorrhoeae transmission in men who have sex with men: towards individualised diagnosis and treatment.

Zienkiewicz AK, Verschueren van Rees N, Homer M, Ong JJ, Christensen H, Hill D, Looker KJ, Horner P, Hughes G, Turner KME. (Full Text)

Sex Health. 2019 Sep 3. doi: 10.1071/SH18235. [Epub ahead of print]


Background: Antimicrobial-resistant (AMR) gonorrhoea is a global public health threat. Discriminatory point-of-care tests (POCT) to detect drug sensitivity are under development, enabling individualised resistance-guided therapy. Methods: An individual-based dynamic transmission model of gonorrhoea infection in MSM living in London has been developed, incorporating ciprofloxacin-sensitive and resistant strains. The time-dependent sexual contact network is captured by periodically restructuring active connections to reflect the transience of contacts. Different strategies to improve treatment selection were explored, including discriminatory POCT and selecting partner treatment based on either the index case or partner susceptibility. Outcomes included population prevalence of gonorrhoea and drug dose counts. Results: It is shown that using POCT to detect ciprofloxacin-sensitive infections could result in a large decrease in ceftriaxone doses (by 70% compared with the reference case in the simulations of this study). It also suggests that ceftriaxone use can be reduced with existing technologies, albeit to a lesser degree; either using index case sensitivity profiles to direct treatment of partners, or testing notified partners with strain discriminatory laboratory tests before treatment, reduced ceftriaxone use in our model (by 27% and 47% respectively). Conclusions: POCT to detect ciprofloxacin-sensitive gonorrhoea are likely to dramatically reduce reliance on ceftriaxone, but requires the implementation of new technology. In the meantime, the proportion of unnecessary ceftriaxone treatment by testing partners before treatment could be reduced significantly. Alternatively, index case sensitivity profiles could be used to select effective treatments for partners.


Novel antibiotics, mechanisms, vaccines, and other advances

Gentamicin 240 mg plus azithromycin 2 g vs. ceftriaxone 500 mg plus azithromycin 2 g for treatment of rectal and pharyngeal gonorrhoea: a randomized controlled trial.

Rob F, Klubalová B, Nyčová E, Hercogová J, Unemo M. 

Clin Microbiol Infect. 2019 Aug 14. pii: S1198-743X(19)30443-4. doi: 10.1016/j.cmi.2019.08.004. [Epub ahead of print]



To evaluate the efficacy and tolerability of gentamicin 240 mg plus azithromycin 2 g for treatment of uncomplicated rectal and pharyngeal gonorrhoea compared to ceftriaxone 500 mg plus azithromycin 2 g, the recommended European first-line gonorrhoea treatment.


A non-inferiority, open-label, single centre randomized controlled trial was conducted in Prague, Czech Republic. Patients, 18-75 years of age, diagnosed with uncomplicated rectal or pharyngeal gonorrhoea by nucleic acid amplification test (NAAT) were randomized to treatment with gentamicin 240 mg intramuscularly plus azithromycin 2 g orally or ceftriaxone 500 g intramuscularly plus azithromycin 2 g orally. The primary outcome was negative culture and negative NAAT, i.e., one week and three weeks, respectively, after treatment.


Both clinical cure and microbiological clearance was achieved by 100% (95%CI 0.95-1.00) of patients in the gentamicin/azithromycin arm (n=72; 40 rectal, 17 pharyngeal, and 15 rectal+pharyngeal infections both localizations) and 100% (95%CI 0.95-1.00) in ceftriaxone/azithromycin arm (n=71; 38 rectal, 14 pharyngeal, and 19 rectal+pharyngeal infections). The absolute difference between the two arms was 0.0% (CI95% -5.1 to 5.1), thus less than the pre-specified margin of 7%. Administration of gentamicin was not more painful than ceftriaxone according to the visual analog scale (1.8 vs. 3.4; p<0.001). Gastrointestinal adverse events were similar in the ceftriaxone arm (33/71, 46.5%) and the gentamicin arm (29/72, 40.3%), and overall in most (52/62, 83.9%) cases they were mild.


Gentamicin 240 mg plus azithromycin 2 g is an effective alternative for treatment of extragenital gonorrhoea.

Advancing vaccine development for gonorrhoea and the Global STI Vaccine Roadmap.

Gottlieb SL, Jerse AE, Delany-Moretlwe S, Deal C, Giersing BK. (Full Text)

Sex Health. 2019 Sep 3. doi: 10.1071/SH19060. [Epub ahead of print]


Efforts to develop vaccines against Neisseria gonorrhoeae have become increasingly important, given the rising threat of gonococcal antimicrobial resistance (AMR). Recent data suggest vaccines for gonorrhoea are biologically feasible; in particular, epidemiological evidence shows that vaccines against a closely related pathogen, serogroup B Neisseria meningitidis outer membrane vesicle (OMV) vaccines, may reduce gonorrhoea incidence. Vaccine candidates using several approaches are currently in preclinical development, including meningococcal and gonococcal OMV vaccines, a lipooligosaccharide epitope and purified protein subunit vaccines. The Global STI Vaccine Roadmap provides action steps to build on this technical momentum and advance gonococcal vaccine development. Better quantifying the magnitude of gonorrhoea-associated disease burden, for outcomes like infertility, and modelling the predicted role of gonococcal vaccines in addressing AMR will be essential for building a full public health value proposition, which can justify investment and help with decision making about future vaccine policy and programs. Efforts are underway to gain consensus on gonorrhoea vaccine target populations, implementation strategies and other preferred product characteristics that would make these vaccines suitable for use in low- and middle-income, as well as high-income, contexts. Addressing these epidemiological, programmatic and policy considerations in parallel to advancing research and development, including direct assessment of the ability of meningococcal B OMV vaccines to prevent gonorrhoea, can help bring about the development of viable gonococcal vaccines.

Immunomodulatory potential of polysaccharides from Coriolus versicolor against intracellular bacteria Neisseria gonorrhoeae.

Pramudya M, Wahyuningsih SPA. (Full Text)

Vet World. 2019 Jun;12(6):735-739. doi: 10.14202/vetworld.2019.735-739. Epub 2019 Jun 1.



For many years, people use natural products from the plant and fungal to improve immune response against microorganism. This study aimed to investigate the immunomodulatory properties of polysaccharides (PS) from Coriolus versicolor in mice infected by intracellular bacteria Neisseria gonorrhoeae.


Thirty-six female BALB/C mice were divided into six groups: Normal control, negative control, positive control, P1 (PS before infection), P2 (PS after infection), and P3 (PS before and after infection). PS were administrated for 10 days. N. gonorrhoeae was infected twice with 2 weeks gap from the first to second exposure with a dose of 106 cells. 1 week after the end of treatment, level of oxidants, innate immune responses, and adaptive immune responses were measured.


This study showed that PS administration could restore the number of leukocytes as normal but could not enhance the number of phagocytes and its activity. PS administration also showed immunosuppression activity by lowering nitric oxide levels in P2 and P3 groups (p<0.05). This result showed that PS prevent over-expression of pro-inflammatory cytokines by decreasing phagocytic activity. Contrast with innate immune response result; PS administration could significantly increase interferon-gamma level in P1, P2, and P3 groups (p<0.05). Level of antibodies was significantly increased in the P3 group (p<0.05). PS administration also showed an increased level of tumor necrosis factor-α, but the difference was not significant (p>0.05).


PS enhance adaptive immunity due to the capability of N. gonorrhoeae that able to survive and replicate in phagocytes. Thus, PS from C. versicolor could be potentially be used as a natural immunomodulator against intracellular bacteria.

Cationic cell-penetrating peptide is bactericidal against Neisseria gonorrhoeae.

John CM, Li M, Feng D, Jarvis GA. (Full Text)

J Antimicrob Chemother. 2019 Aug 19. pii: dkz339. doi: 10.1093/jac/dkz339. [Epub ahead of print]



Cell-penetrating peptides (CPPs) have been evaluated for intracellular delivery of molecules and several CPPs have bactericidal activity. Our objectives were to determine the effect of a 12 amino acid CPPs on survival and on the invasive and inflammatory potential of Neisseria gonorrhoeae.


Survival of MDR and human challenge strains of N. gonorrhoeae grown in cell culture medium with 10% FBS was determined after treatment with the CPP and human antimicrobial peptide LL-37 for 4 h. Confocal microscopy was used to examine penetration of FITC-labelled CPP into bacterial cells. The ability of the CPP to prevent invasion of human ME-180 cervical epithelial cells and to reduce the induction of TNF-α in human THP-1 monocytic cells in response to gonococcal infection was assessed. Cytotoxicity of the CPP towards the THP-1 cells was determined.


The CPP was bactericidal, with 95%-100% killing of all gonococcal strains at 100 μM. Confocal microscopy of gonococci incubated with FITC-labelled CPP revealed the penetration of the peptide. CPP treatment of N. gonorrhoeae inhibited gonococcal invasion of ME-180 cells and reduced the expression of TNF-α induced in THP-1 cells by gonococci. The CPP showed no cytotoxicity towards human THP-1 cells.


Based on these promising results, future studies will focus on testing of CPP in the presence of other types of host cells and exploration of structural modifications of the CPP that could decrease its susceptibility to proteolysis and increase its potency.

Mechanistic Insight Into the Activation of the NLRP3 Inflammasome by Neisseria gonorrhoeae in Macrophages.

Li LH, Lin JS, Chiu HW, Lin WY, Ju TC, Chen FH, Chernikov OV, Liu ML, Chang JC, Hsu CH, Chen A, Ka SM, Gao HW, Hua KF. (Full Text)

Front Immunol. 2019 Jul 31;10:1815. doi: 10.3389/fimmu.2019.01815. eCollection 2019.


Gonorrhea is a type III legal communicable disease caused by Neisseria gonorrhoeae (NG), one of the most common sexually transmitted bacteria worldwide. NG infection can cause urethritis or systemic inflammation and may lead to infertility or other complications. The NACHT, LRR, and PYD domains-containing protein 3 (NLRP3) inflammasome is a protein complex composed of NLRP3, apoptosis-associated speck-like protein and caspase-1 and is an important part of the cellular machinery controlling the release of interleukin (IL)-1β and IL-18 and the pathogenesis of numerous infectious diseases. It has been reported that NG infection activates the NLRP3 inflammasome; however, the underlying mechanism remain unclear. In this report, the signaling pathways involved in the regulation of NG-mediated NLRP3 inflammasome activation in macrophages were studied. The results indicated that viable NG, but not heat-killed or freeze/thaw-killed NG, activated the NLRP3 inflammasome in macrophages through toll-like receptor 2, but not toll-like receptor 4. NG infection provided the priming signal to the NLRP3 inflammasome that induced the expression of NLRP3 and IL-1β precursor through the nuclear factor kappa B and mitogen-activated protein kinase pathways. In addition, NG infection provided the activation signal to the NLRP3 inflammasome that activated caspase-1 through P2X7 receptor-dependent potassium efflux, lysosomal acidification, mitochondrial dysfunction, and reactive oxygen species production pathways. Furthermore, we demonstrated that NLRP3 knockout increased phagocytosis of bacteria by macrophages and increases the bactericidal activity of macrophages against NG. These findings provide potential molecular targets for the development of anti-inflammatory drugs that could ameliorate NG-mediated inflammation.

Could Dampening Expression of the Neisseria gonorrhoeae mtrCDE-Encoded Efflux Pump Be a Strategy To Preserve Currently or Resurrect Formerly Used Antibiotics To Treat Gonorrhea?

Chen S, Connolly KL, Rouquette-Loughlin C, D'Andrea A, Jerse AE, Shafer WM. (Full Text)

MBio. 2019 Aug 13;10(4). pii: e01576-19. doi: 10.1128/mBio.01576-19.


Neisseria gonorrhoeae has developed resistance to every antibiotic introduced for treatment of gonorrhea since 1938, and concern now exists that gonorrheal infections may become refractory to all available antibiotics approved for therapy. The current recommended dual antibiotic treatment regimen of ceftriaxone (CRO) and azithromycin (AZM) is threatened with the emergence of gonococcal strains displaying resistance to one or both of these antibiotics. Non-beta-lactamase resistance to penicillin and third-generation cephalosporins, as well as low-level AZM resistance expressed by gonococci, requires overexpression of the mtrCDE-encoded efflux pump, which in wild-type (WT) strains is subject to transcriptional repression by MtrR. Since earlier studies showed that loss of MtrCDE renders gonococci hypersusceptible to beta-lactams and macrolides, we hypothesized that transcriptional dampening of mtrCDE would render an otherwise resistant strain susceptible to these antibiotics as assessed by antibiotic susceptibility testing and during experimental infection. In order to test this hypothesis, we ectopically expressed a WT copy of the mtrR gene, which encodes the repressor of the mtrCDE efflux pump operon, in N. gonorrhoeae strain H041, the first reported gonococcal strain to cause a third-generation-cephalosporin-resistant infection. We now report that MtrR production can repress the expression of mtrCDE, increase antimicrobial susceptibility in vitro, and enhance beta-lactam efficacy in eliminating gonococci as assessed in a female mouse model of lower genital tract infection. We propose that strategies that target the MtrCDE efflux pump should be considered to counteract the increasing problem of antibiotic-resistant gonococci.

IMPORTANCE The emergence of gonococcal strains resistant to past or currently used antibiotics is a global public health concern, given the estimated 78 million infections that occur annually. The dearth of new antibiotics to treat gonorrhea demands that alternative curative strategies be considered to counteract antibiotic resistance expressed by gonococci. Herein, we show that decreased expression of a drug efflux pump that participates in gonococcal resistance to antibiotics can increase gonococcal susceptibility to beta-lactams and macrolides under laboratory conditions, as well as improve antibiotic-mediated clearance of gonococci from the genital tract of experimentally infected female mice.