Neisseria gonorrhoeae FC428 Subclone, Vietnam, 2019-2020

Ceftriaxone-Resistant Gonorrhea - China, 2022

Gonorrhea is a widespread sexually transmitted infection; in 2022, China reported 96,313 cases of gonorrhea, making it the fourth most common notifiable infectious disease in the country after viral hepatitis, pulmonary tuberculosis, and syphilis. The rise in prevalence in antimicrobial-resistant strains, particularly the international spread of ceftriaxone-resistant clones, poses a formidable challenge to gonorrhea control. The China Gonococcal Resistance Surveillance Program (China-GRSP), established in 1987 and covering 19 of 34 provincial-level administrative units, continuously monitors gonococcal antimicrobial resistance. In 2022, 13 China-GRSP sentinel sites collected 2,804 gonococcal isolates, representing 2.9% of all cases reported in China, and 4.1% of cases reported in the 13 participating provinces. The prevalence of Neisseria gonorrhoeae resistance to ceftriaxone was 8.1%, approximately three times the 2017 rate of 2.9%; five provinces reported >10% ceftriaxone resistance. Resistance prevalences to cefixime, azithromycin, tetracycline, penicillin, and ciprofloxacin were 16.0%, 16.9%, 77.1%, 77.8%, and 97.6%, respectively. Only one case of spectinomycin resistance was reported. These data highlight a substantial increase in ceftriaxone resistance from 2017 to 2022. Effective diagnosis and treatment and appropriate management of sex partners are essential to protect the health of infected persons and prevent ongoing transmission of gonorrhea, including transmission of resistant strains. Identifying reasons for the spread of ceftriaxone-resistant N. gonorrhoeae in China could guide strategies, such as antibiotic stewardship, to mitigate the rising resistance rate and curb the spread of resistant strains.

Bacitracin enhances ceftriaxone susceptibility of the high-level ceftriaxone-resistant gonococcal FC428 clone

IMPORTANCE

Ceftriaxone-based antimicrobial therapies for gonorrhea are threatened by waning ceftriaxone susceptibility levels and the global dissemination of the high-level ceftriaxone-resistant gonococcal FC428 clone. Combination therapy can be an effective strategy to restrain the development of ceftriaxone resistance, and for that purpose, it is important to find an alternative antimicrobial to replace azithromycin, which has recently been removed in some countries from the recommended ceftriaxone plus azithromycin dual-antimicrobial therapy. Ideally, the second antimicrobial should display synergistic activity with ceftriaxone. We hypothesized that bacitracin might display synergistic activity with ceftriaxone because of their distinct mechanisms targeting bacterial cell wall synthesis. In this study, we showed that bacitracin indeed displays synergistic activity with ceftriaxone against Neisseria gonorrhoeae. Importantly, strains associated with the FC428 clone appeared to be particularly susceptible to the bacitracin plus ceftriaxone combination, which might therefore be an interesting dual therapy for further in vivo testing.

Th1-polarized MtrE-based gonococcal vaccines display prophylactic and therapeutic efficacy

ABSTRACTGlobal dissemination of high-level ceftriaxone-resistant Neisseria gonorrhoeae strains associated with the FC428 clone poses a threat to the efficacy ceftriaxone-based therapies. Vaccination is the best strategy to contain multidrug-resistant infections. In this study, we investigated the efficacy of MtrE and its surface Loop2 as vaccine antigens when combined with a Th1-polarizing adjuvant, which is expected to be beneficial for gonococcal vaccine development. Using in vitro dendritic cell maturation and T cell differentiation assays, CpG1826 was identified as the optimal Th1-polarizing adjuvant for MtrE and Loop2 displayed as linear epitope (Nloop2) or structural epitope (Intraloop2) on a carrier protein. Loop2-based antigens raised strongly Th1-polarized and bactericidal antibody responses in vaccinated mice. Furthermore, the vaccine formulations provided protection against a gonococcal challenge in mouse vaginal tract infection model when provided as prophylactic vaccines. Also, the vaccine formulations accelerated gonococcal clearance when provided as a single therapeutic dose to treat an already established infection, including against a strain associated with the FC428 clone. Therefore, this study demonstrated that MtrE and Loop 2 are effective gonococcal vaccine antigens when combined with the Th1-polarizing CpG1826 adjuvant.

Genomic epidemiology of Neisseria gonorrhoeae in Shenzhen, China, during 2019-2020: increased spread of ceftriaxone-resistant isolates brings insights for strengthening public health responses

The antimicrobial resistance (AMR) in gonorrhea poses global threat of increasing public health concern. In response to this concern, molecular surveillance has been widely utilized to detail the changes in the evolution and distribution of Neisseria gonorrhoeae during AMR transmission. In this study, we performed a comprehensive molecular surveillance of 664 N. gonorrhoeae isolates collected in Shenzhen, one of the cities with the largest mobile population in China, 2019-2020. In 2020, ceftriaxone showed an unprecedented high resistance rate of 24.87%, and 67.83% of the ceftriaxone-resistant (Cro-R) isolates harbored a nonmosaic penA allele. The Cro-R isolates with nonmosaic penA alleles showed a tremendous increasing trend from 0.00% in 2014 to 20.45% in 2020, which proves the need for monitoring nonmosaic penA-related resistance. Importantly, genotyping indicated that multilocus sequence typing ST11231 (35.71%) had a notable rate of ceftriaxone resistance, which might become the focus of future surveillance. Whole-genome sequencing analysis showed that the internationally spreading FC428 clones have circulated in Shenzhen region with typical ceftriaxone resistance (MIC ≥ 0.5 mg/L) maintained. Our surveillance combined with genomic analysis provides current information to update gonorrhea management guidelines and emphasizes that continuous AMR surveillance for N. gonorrhoeae is essential. IMPORTANCE We conducted a comprehensive molecular epidemiology analysis for antimicrobial-resistant Neisseria gonorrhoeae in Shenzhen during 2019-2020, which provided important data for personalized treatment and adjustment of monitoring strategy. Briefly, the proportion of ceftriaxone-resistant (Cro-R) isolates reached a stunning prevalence rate of 24.87% in 2020. A typical increment of Cro-R isolates with nonmosaic penA alleles proves the necessity of monitoring nonmosaic AMR mechanism and involving it into developing molecular detection methods. Whole-genome sequencing analysis showed that the international spreading FC428 clone has been circulating in Shenzhen with typical ceftriaxone resistance (MIC ≥ 0.5 mg/L) maintained. In summary, we conducted a comprehensive epidemiology study, providing significant data for therapy management. Our results not only improve the understanding of the distribution and transmission of AMR in N. gonorrhoeae but also provide effective AMR data for improving surveillance strategies in China.

High-level in vitro resistance to gentamicin acquired in a stepwise manner in Neisseria gonorrhoeae

OBJECTIVES

Gentamicin is used in several alternative treatments for gonorrhoea. Verified clinical Neisseria gonorrhoeae isolates with gentamicin resistance are mainly lacking and understanding the mechanisms for gonococcal gentamicin resistance is imperative. We selected gentamicin resistance in gonococci in vitro, identified the novel gentamicin-resistance mutations, and examined the biofitness of a high-level gentamicin-resistant mutant.

METHODS

Low- and high-level gentamicin resistance was selected in WHO X (gentamicin MIC = 4 mg/L) on gentamicin-gradient agar plates. Selected mutants were whole-genome sequenced. Potential gentamicin-resistance fusA mutations were transformed into WT strains to verify their impact on gentamicin MICs. The biofitness of high-level gentamicin-resistant mutants was examined using a competitive assay in a hollow-fibre infection model.

RESULTS

WHO X mutants with gentamicin MICs of up to 128 mg/L were selected. Primarily selected fusA mutations were further investigated, and fusAR635L and fusAM520I + R635L were particularly interesting. Different mutations in fusA and ubiM were found in low-level gentamicin-resistant mutants, while fusAM520I was associated with high-level gentamicin resistance. Protein structure predictions showed that fusAM520I is located in domain IV of the elongation factor-G (EF-G). The high-level gentamicin-resistant WHO X mutant was outcompeted by the gentamicin-susceptible WHO X parental strain, suggesting lower biofitness.

CONCLUSIONS

We describe the first high-level gentamicin-resistant gonococcal isolate (MIC = 128 mg/L), which was selected in vitro through experimental evolution. The most substantial increases of the gentamicin MICs were caused by mutations in fusA (G1560A and G1904T encoding EF-G M520I and R635L, respectively) and ubiM (D186N). The high-level gentamicin-resistant N. gonorrhoeae mutant showed impaired biofitness.

Increase in Multidrug Resistant Neisseria gonorrhoeae FC428-Like Isolates Harboring the Mosaic penA 60.001 Gene, in Nanjing, China (2017-2020)

Background

Since the first Chinese report of the ceftriaxone-resistant Neisseria gonorrhoeae FC428 clone in 2016, additional FC428-like, penA 60.001 isolates have been identified in China.

Objective

To document the rise in penA 60.001 isolates in Nanjing, China, and characterize their molecular and epidemiological features.

Methods

N. gonorrhoeae minimum inhibitory concentrations (MICs, mg/L) for ceftriaxone, cefixime, penicillin, tetracycline, ciprofloxacin, azithromycin, spectinomycin, gentamicin and zoliflodacin were determined by agar dilution. MICs for ertapenem were measured by E-test. N. gonorrhoeae antimicrobial sequence typing (NG-STAR) of seven loci (penA, mtrR, porB, ponA, gyrA, parC and 23S rRNA) was analyzed together with N. gonorrhoeae multiantigen sequence typing (NG-MAST) and multilocus sequence typing (MLST). Phylogenetic analysis was also performed using whole genomic sequencing (WGS).

Results

Fourteen FC428-related penA 60.001 N. gonorrhoeae infections were identified out of 677 infections from 2017 to 2020, in Nanjing, representing an incremental yearly rise in the percentage of the city's N. gonorrhoeae isolates that were FC428-related. Seven FC428-related N. gonorrhoeae infections were acquired in Nanjing, proper; four others in eastern Chinese cities and three from unknown locations. All FC428-related isolates were resistant to ceftriaxone, cefixime, ciprofloxacin, tetracycline and penicillin but susceptible to spectinomycin, gentamicin, ertapenem and zoliflodacin; three strains were resistant to azithromycin. penA 60.001 isolates displayed closely related MLST types and NG-STAR types but relatively distant NG-MAST types. WGS showed a phylogenetic analysis that intermingled with other international isolates.

Conclusion

penA 60.001 N. gonorrhoeae isolates emerged in Nanjing, China, beginning in 2017, and have continued to rise.

Antimicrobial Activity of Auranofin, Cannabidivarin, and Tolfenamic Acid against Multidrug-Resistant Neisseria gonorrhoeae

Alternative antimicrobial therapies are urgently required for the multidrug-resistant bacterial pathogen Neisseria gonorrhoeae, for which currently ceftriaxone is the only remaining recommended first-line therapy. Repurposing of drugs that are approved for other clinical applications offers an efficient approach for development of alternative antimicrobial therapies. Auranofin, cannabidivarin, and tolfenamic acid were recently identified to display antimicrobial activity against N. gonorrhoeae. Here, we investigated their activity against a collection of 575 multidrug-resistant clinical isolates. All three compounds displayed consistent antimicrobial activity against all isolates, including against strains associated with the high-level ceftriaxone-resistant FC428 clone, with both the mode and MIC90 for auranofin of 0.5 mg/L, while both the mode and MIC90 for cannabidivarin and tolfenamic acid were 8 mg/L. Correlations between MICs of ceftriaxone and auranofin, cannabidivarin or tolfenamic acid were low, indicating that development of cross-resistance is unlikely. Furthermore, antimicrobial synergy analysis between ceftriaxone and auranofin, cannabidivarin, or tolfenamic acid by determination of the fractional inhibitory concentration index (FICI) resulted in an interpretation of indifference. Finally, time-kill analyses showed that all three compounds are bactericidal against both the N. gonorrhoeae ATCC 49226 reference strain and an FC428-associated clinical isolate, with particularly cannabidivarin displaying rapid bactericidal activity. Overall, auranofin, cannabidivarin, and tolfenamic acid displayed consistent antimicrobial activity against multidrug-resistant N. gonorrhoeae, warranting further exploration of their suitability as alternative antimicrobials for treatment of gonococcal infections. IMPORTANCE Neisseria gonorrhoeae is a major public health concern because of the high incidence of gonorrhea and the increasingly limited options for antimicrobial therapy. Strains associated with the FC428 clone are a particular concern because they have shown global dissemination and they display high-level resistance against the currently recommended ceftriaxone therapy. Therefore, development of alternative antimicrobial therapies is urgently required to ensure treatment of gonorrhea remains available in the future. Repurposing of clinically approved drugs could be a rapid approach for the development of such alternative antimicrobials. In this study, we showed that repurposing of auranofin, cannabidivarin, and tolfenamic acid for antimicrobial therapy of gonorrhea deserves further clinical explorations because these compounds displayed consistent antimicrobial activity against a large collection of contemporary multidrug-resistant gonococcal isolates that included strains associated with the FC428 clone.

Detection of 10 cases of ceftriaxone-resistant Neisseria gonorrhoeae in the United Kingdom, December 2021 to June 2022

Between December 2021 and June 2022, 10 cases of ceftriaxone-resistant Neisseria gonorrhoeae (ST8123; n = 8) were detected in the United Kingdom, compared with nine cases during the previous 6 years. Most of these cases were associated with travel from the Asia-Pacific region; all were heterosexual people, with most in their 20s. Although all cases were successfully treated, not all partners of cases could be traced, and there is a risk of further transmission of ceftriaxone-resistant gonococcal infection within the UK.

Molecular Mechanisms of Drug Resistance and Epidemiology of Multidrug-Resistant Variants of Neisseria gonorrhoeae

The paper presents various issues related to the increasing drug resistance of Neisseria gonorrhoeae and the occurrence and spread of multidrug-resistant clones. One of the most important is the incidence and evolution of resistance mechanisms of N. gonorrhoeae to beta-lactam antibiotics. Chromosomal resistance to penicillins and oxyimino-cephalosporins and plasmid resistance to penicillins are discussed. Chromosomal resistance is associated with the presence of mutations in the PBP2 protein, containing mosaic variants and nonmosaic amino acid substitutions in the transpeptidase domain, and their correlation with mutations in the mtrR gene and its promoter regions (the MtrCDE membrane pump repressor) and in several other genes, which together determine reduced sensitivity or resistance to ceftriaxone and cefixime. Plasmid resistance to penicillins results from the production of beta-lactamases. There are different types of beta-lactamases as well as penicillinase plasmids. In addition to resistance to beta-lactam antibiotics, the paper covers the mechanisms and occurrence of resistance to macrolides (azithromycin), fluoroquinolones and some other antibiotics. Moreover, the most important epidemiological types of multidrug-resistant N. gonorrhoeae, prevalent in specific years and regions, are discussed. Epidemiological types are defined as sequence types, clonal complexes and genogroups obtained by various typing systems such as NG-STAR, NG-MAST and MLST. New perspectives on the treatment of N. gonorrhoeae infections are also presented, including new drugs active against multidrug-resistant strains.

Moenomycin is broadly active against multidrug-resistant Neisseria gonorrhoeae and clears an infection from a murine vaginal tract infection model

OBJECTIVES

Ceftriaxone therapy for gonorrhoea has become under increasing pressure due to waning susceptibility levels and emergence of high-level resistant strains such as the FC428 clone. Moenomycin was recently identified to display potent anti-gonococcal activity against some reference strains. Therefore, the aim of this study was to investigate moenomycin in vitro and in vivo antimicrobial activity.

METHODS

Moenomycin in vitro antimicrobial activity was investigated against 575 clinical isolates, including strains associated with the FC428 clone, using the agar dilution method. Moenomycin in vivo activity was investigated in a mouse vaginal tract gonococcal infection model.

RESULTS

The moenomycin MIC range for the strain collection was 0.004-0.06 mg/L, with a MIC50 of 0.016 mg/L and a MIC90 of 0.03 mg/L. The correlation between moenomycin and ceftriaxone susceptibility levels was poor (R = 0.13), while the fractional inhibitory concentration index (FICI) resulted in indifference for all tested strains. Therefore, development of cross-resistance between moenomycin and ceftriaxone is unlikely for N. gonorrhoeae. Determination of the moenomycin mode of activity against N. gonorrhoeae by time-kill assays showed that moenomycin is bactericidal, with over 104-fold inactivation observed after 4 h exposure. Finally, an intramuscular moenomycin dose of 10 mg/kg given on 2 consecutive days was able to clear a gonococcal infection in a mouse vaginal tract infection model within 1-3 days after the second dose, which was significantly faster than for mice treated with the vehicle control (P < 0.0001).

CONCLUSIONS

Moenomycin displays potent in vitro and in vivo antimicrobial activity against N. gonorrhoeae, warranting further exploration as alternative therapy.