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

Neisseria gonorrhoeae antimicrobial resistance (AMR) monthly UPDATES

October, 2019

Reviews and Commentary 

Gonorrhoea: Tackling the Global Epidemic in the Era of Rising Antimicrobial Resistance

Ong JJ, Wi T, Hughes G, Williamson DA, Mayaud P, Chow EPF. 

Sex Health. Volume 16. Issue 5. 2019.


Epidemiology and Surveillance

Six penA codons accurately and reliably predict cefixime-decreased susceptibility in Neisseria gonorrhoeae.

Deng X, Klausner JD. (Full Text)

J Infect Dis. 2019 Oct 3. pii: jiz504. doi: 10.1093/infdis/jiz504. [Epub ahead of print]

Genomic characterization of novel Neisseria species.

Diallo K, MacLennan J, Harrison OB, Msefula C, Sow SO, Daugla DM, Johnson E, Trotter C, MacLennan CA, Parkhill J, Borrow R, Greenwood BM, Maiden MCJ. (Full Text)

Sci Rep. 2019 Sep 24;9(1):13742. doi: 10.1038/s41598-019-50203-2.


Of the ten human-restricted Neisseria species two, Neisseria meningitidis, and Neisseria gonorrhoeae, cause invasive disease: the other eight are carried asymptomatically in the pharynx, possibly modulating meningococcal and gonococcal infections. Consequently, characterizing their diversity is important for understanding the microbiome in health and disease. Whole genome sequences from 181 Neisseria isolates were examined, including those of three well-defined species (N. meningitidis; N. gonorrhoeae; and Neisseria polysaccharea) and genomes of isolates unassigned to any species (Nspp). Sequence analysis of ribosomal genes, and a set of core (cgMLST) genes were used to infer phylogenetic relationships. Average Nucleotide Identity (ANI) and phenotypic data were used to define species clusters, and morphological and metabolic differences among them. Phylogenetic analyses identified two polyphyletic clusters (N. polysaccharea and Nspp.), while, cgMLST data grouped Nspp isolates into nine clusters and identified at least three N. polysaccharea clusters. ANI results classified Nspp into seven putative species, and also indicated at least three putative N. polysaccharea species. Electron microscopy identified morphological differences among these species. This genomic approach provided a consistent methodology for species characterization using distinct phylogenetic clusters. Seven putative novel Neisseria species were identified, confirming the importance of genomic studies in the characterization of the genus Neisseria.

High in vitro susceptibility to the first-in-class spiropyrimidinetrione zoliflodacin among consecutive clinical Neisseria gonorrhoeae isolates from Thailand (2018) and South Africa (2015-2017).

Jacobsson S, Kularatne R, Kittiyaowamarn R, Maseko V, Paopang P, Sangprasert P, Sirivongrangson P, Piddock L, Wi T, Alirol E, Unemo M. (Full Text)

Antimicrob Agents Chemother. 2019 Sep 23. pii: AAC.01479-19. doi: 10.1128/AAC.01479-19. [Epub ahead of print]


We evaluated the in vitro susceptibility to the first-in-class spiropyrimidinetrione zoliflodacin among recent consecutive clinical Neisseria gonorrhoeae isolates cultured in Thailand (n=99; 2018) and South Africa (n=100; 2015-2017). Zoliflodacin was highly active in vitro against all tested isolates (MIC range: 0.004-0.25; MIC50: 0.064, MIC90: 0.125 μg/ml), with no cross-resistance to any of the seven comparator antimicrobials. Our data support the initiation of the global zoliflodacin phase 3 randomized controlled clinical trial for uncomplicated gonorrhea.

Epidemiology, molecular characterisation and antimicrobial susceptibility of Neisseria gonorrhoeae isolates in Madrid, Spain, in 2016.

Guerrero-Torres MD, Menéndez MB, Guerras CS, Tello E, Ballesteros J, Clavo P, Puerta T, Vera M, Ayerdi O, Carrio JC, Mozo I, Del Romero J, Vázquez JA, Abad R. (Full Text)

Epidemiol Infect. 2019 Sep 24;147:e274. doi: 10.1017/S095026881900150X.


With the aim to elucidate gonococcal antimicrobial resistance (AMR)-risk factors, we undertook a retrospective analysis of the molecular epidemiology and AMR of 104 Neisseria gonorrhoeae isolates from clinical samples (urethra, rectum, pharynx and cervix) of 94 individuals attending a sexually transmitted infection clinic in Madrid (Spain) from July to October 2016, and explored potential links with socio-demographic, behavioural and clinical factors of patients. Antimicrobial susceptibility was determined by E-tests, and isolates were characterised by N. gonorrhoeae multi-antigen sequence typing. Penicillin resistance was recorded for 15.4% of isolates, and most were susceptible to tetracycline, cefixime and azithromycin; a high incidence of ciprofloxacin resistance (~40%) was found. Isolates were grouped into 51 different sequence types (STs) and 10 genogroups (G), with G2400, ST5441, ST2318, ST12547 and G2992 being the most prevalent. A significant association (P = 0.015) was evident between HIV-positive MSM individuals and having a ciprofloxacin-resistant strain. Likewise, a strong association (P = 0.047) was found between patient age of MSM and carriage of isolates expressing decreased susceptibility to azithromycin. A decrease in the incidence of AMR gonococcal strains and a change in the strain populations previously reported from other parts of Spain were observed. Of note, the prevalent multi-drug resistant genogroup G1407 was represented by only three strains in our study, while the pan-susceptible clones such as ST5441, and ST2318, associated with extragenital body sites were the most prevalent.

Identification of an unusual 16S rRNA mutation in Neisseria gonorrhoeae.

Guglielmino CJD, Appleton S, Vohra R, Jennison AV. (Full Text)

J Clin Microbiol. 2019 Sep 11. pii: JCM.01337-19. doi: 10.1128/JCM.01337-19. [Epub ahead of print]

Two cases of multidrug-resistant Neisseria gonorrhoeae related to travel in south-eastern Asia, France, June 2019.

Poncin T, Merimeche M, Braille A, Mainardis M, Bebear C, Jacquier H, Berçot B. (Full Text)

Euro Surveill. 2019 Sep;24(36). doi: 10.2807/1560-7917.ES.2019.24.36.1900528.


We report two cases of multidrug-resistant Neisseria gonorrhoeae urogenital infection with ceftriaxone resistance in a heterosexual couple in south-western France who were successfully treated with a single, high dose of intramuscular ceftriaxone (1 g). Whole genome sequencing of isolate F91 identified MLST13871, NG-MAST1086, NG-STAR233. Patient history revealed the isolate F91 was most likely acquired during a trip to Cambodia and belongs to the successful multidrug-resistant FC428 Asian clone.

Detection and analysis of two cases of the internationally spreading ceftriaxone-resistant Neisseria gonorrhoeae FC428 clone in China.

Yang F, Zhang H, Chen Y, Zhai Y, Zhao F, Yu Y, van der Veen S. (Full Text)

J Antimicrob Chemother. 2019 Aug 29. pii: dkz384. doi: 10.1093/jac/dkz384. [Epub ahead of print]


Novel detection strategies and diagnostics

Variability in azithromycin susceptibility results for Neisseria gonorrhoeae obtained using gradient minimum inhibitory concentration strip and agar dilution techniques.

McAuliffe GN, Smith M, Cooper G, Forster RF, Roberts SA. (Full Text

J Clin Microbiol. 2019 Oct 2. pii: JCM.01353-19. doi: 10.1128/JCM.01353-19. [Epub ahead of print]


Azithromycin is a component of empiric treatment regimens for Neisseria gonorrhoeae (NG) infections but antimicrobial susceptibility testing for this agent is technically challenging. We compared the inter-test variability, MIC values and CLSI/EUCAST categorisation of clinical and reference isolates of NG to azithromycin by testing 107 clinical isolates and nine reference isolates by agar dilution and in duplicate using MIC Test Strip (Liofilchem, Italy) and Etest (bioMerieux, France). Replicate isolate agreement within one log2 between duplicate tests was 87% for MIC Test Strip and 100% for Etest (p<0.001). Essential agreement with agar dilution was higher for Etest (91%) than for MIC Test Strip (44%, p<0.001). The geometric mean MIC was highest for MIC Test Strip (0.8 mg/L) and significantly higher compared with both Etest (0.47 mg/L, p<0.001) and agar dilution (0.26 mg/L, p<0.001). Etest MICs were higher than those obtained with agar dilution (p<0.001). Agar dilution, MIC Test Strip and Etest categorised 96%, 85% and 95% (p=0.003) of clinical isolates respectively as susceptible/wild type by CLSI/EUCAST criteria. Our results illustrate the difficulties underlying azithromycin susceptibility testing for NG and demonstrate that results can vary using different methods. This variability could influence antimicrobial resistance reporting between laboratories involved in NG surveillance programmes.

PacBio Amplicon Sequencing Method To Measure Pilin Antigenic Variation Frequencies of Neisseria gonorrhoeae.

Ozer EA, Prister LL, Yin S, Ward BH, Ivanov S, Seifert HS. (Full Text)

mSphere. 2019 Oct 2;4(5). pii: e00562-19. doi: 10.1128/mSphere.00562-19.


Gene diversification is a common mechanism pathogens use to alter surface structures to aid in immune avoidance. Neisseria gonorrhoeae uses a gene conversion-based diversification system to alter the primary sequence of the gene encoding the major subunit of the pilus, pilE Antigenic variation occurs when one of the nonexpressed 19 silent copies donates part of its DNA sequence to pilE We have developed a method using Pacific Biosciences (PacBio) amplicon sequencing and custom software to determine pilin antigenic variation frequencies. The program analyzes 37 variable regions across the strain FA1090 1-81-S2 pilE gene and can be modified to determine sequence variation from other starting pilE sequences or other diversity generation systems. Using this method, we measured pilin antigenic variation frequencies for various derivatives of strain FA1090 and showed we can also analyze pilin antigenic variation frequencies during macrophage infection.

IMPORTANCE: Diversity generation systems are used by many unicellular organism to provide subpopulations of cell with different properties that are available when needed. We have developed a method using the PacBio DNA sequencing technology and a custom computer program to analyze the pilin antigenic variation system of the organism that is the sole cause of the sexually transmitted infection, gonorrhea.


Novel antibiotics, mechanisms, vaccines, and other advances

Repurposing salicylamide for combating multidrug-resistant Neisseria gonorrhoeae.

Alhashimi M, Mayhoub A, Seleem MN. (Full Text)

Antimicrob Agents Chemother. 2019 Sep 30. pii: AAC.01225-19. doi: 10.1128/AAC.01225-19. [Epub ahead of print]


The U.S. Centers for Disease Control and Prevention (CDC) lists Neisseria gonorrhoeae as one of the most urgent antibiotic-resistant threats in the United States. This is due to the emergence of clinical isolates that have developed resistance to nearly every antibiotic used to treat gonorrhea and highlights the critical need to find new therapeutics. The present study discovered salicylamide, an analgesic and antipyretic drug, has antibacterial activity against 40 different antibiotic-resistant strains of N. gonorrhoeae (MIC 8-32 μg/ml) with low frequency of resistance <2.4x10-9 Interestingly, salicylamide did not inhibit growth of bacterial species in the vaginal microflora involved in defense against gonococcal infections, such as Lactobacillus gasseri, L. jensenii, L. johnsonii, and L. crispatus. A time-kill assay revealed that salicylamide is a rapidly bactericidal drug as it eradicated a high inoculum of N. gonorrhoeae within 10 hours. Salicylamide was superior to the drug of choice, ceftriaxone, in reducing the burden of intracellular N. gonorrhoeae by 97% in infected endocervical cells. Furthermore, salicylamide outperformed ceftriaxone in reducing expression of the pro-inflammatory cytokine IL-8 from endocervical cells infected with N. gonorrhoeae. A checkerboard assay revealed that salicylamide exhibited a synergistic interaction with tetracycline and an additive relationship with azithromycin and ciprofloxacin, and ceftriaxone. A more in-depth investigation of the structure-activity-relationship of derivatives of salicylamide revealed the amide and hydroxyl groups are important for anti-gonorrheal activity. In conclusion, this study identified salicylamide as a promising candidate for further investigation as a novel treatment option for multidrug-resistant gonorrhea.

Two distinct L-lactate dehydrogenases play a role in the survival of Neisseria gonorrhoeae in cervical epithelial cells.

Chen NH, Ong CY, O'Sullivan J, Ibranovic I, Davey K, Edwards JL, McEwan AG. (Full Text)

J Infect Dis. 2019 Sep 21. pii: jiz468. doi: 10.1093/infdis/jiz468. [Epub ahead of print]


L-lactate is an abundant metabolite in a number of niches in host organisms and represents an important carbon source for bacterial pathogens such as Neisseria gonorrhoeae. Here, we describe an alternative, iron-sulfur cluster-containing L-lactate dehydrogenase, LutACB, that is distinct from the flavoprotein L-lactate dehydrogenase, LldD. Expression of lutACB was found to be positively regulated by iron, whereas lldD was more highly expressed under conditions of iron-limitation. The functional role of LutACB and LldD was reflected in in vitro studies of growth and in the survival of Neisseria gonorrhoeae in primary cervical epithelial cells.

Development of New Antimicrobials for Urogenital Gonorrhea Therapy: Clinical Trial Design Considerations.

Hook EW, Newman L, Drusano G, Evans S, Handsfield HH, Jerse AE, Kong FYS, Lee JY, Taylor SN, Deal C. (Full Text)

Clin Infect Dis. 2019 Sep 20. pii: ciz899. doi: 10.1093/cid/ciz899. [Epub ahead of print]


Gonorrhea remains a major public health challenge and current recommendations for gonorrhea treatment are threatened by evolving antimicrobial resistance and a diminished pipeline for new antibiotics. Evaluations of potential new treatments for gonorrhea currently make limited use of new understanding of the pharmacokinetics/pharmacodynamics contributors to effective therapy and to prevention of antimicrobial resistance, to newer designs for Phase -2 and -3 clinical trials, and is hampered by the requirement to utilize currently recommended combination ceftriaxone/azithromycin therapy as the comparator regimen in non-inferiority trials designed to seek an indication for gonorrhea therapy. Evolving gonococcal epidemiology and clinical trial design constraints likewise hinder enrollment of populations at greatest risk for gonorrhea (adolescents, women, persons infected with antibiotic resistant Neisseria gonorrhoeae). This Viewpoint summarizes a recent meeting to re-consider the evaluation process for antimicrobials for urogenital gonorrhea treatment and highlights these themes to encourage consideration of new designs for evaluation of gonorrhea therapy.