Antimicrobial Susceptibility of Ertapenem in Neisseria gonorrhoeae Isolates Collected Within the China Gonococcal Resistance Surveillance Programme (China-GRSP) 2018

Identification of ceftriaxone-resistant Neisseria gonorrhoeae FC428 clone and isolates harboring a novel mosaic penA gene in Chengdu in 2019-2020

BACKGROUND

Antimicrobial resistance in gonorrhea has become a growing global public health burden. Neisseria gonorrhoeae isolates with resistance to ceftriaxone, the last remaining first-line option, represent an emerging threat of untreatable gonorrhea.

METHODS

A total of ten ceftriaxone-resistant N. gonorrhoeae FC428 isolates and two isolates harboring a novel mosaic penA-232.001 allele from 160 gonococcal isolates in Chengdu in 2019-2020 was described in the present study. Multilocus sequence typing (MLST) and N. gonorrhoeae sequence typing for antimicrobial resistance (NG-STAR) were performed to characterize the isolates. Whole genome sequencing and maximum-likelihood method were performed to infer how the genetic phylogenetic tree of these isolates looks like. Recombination analysis was performed using the RDP4 software. This study was registered in the Chinese Clinical Trial Registry (ChiCTR2100048771, registration date: 20210716).

RESULTS

The genetic phylogeny showed that the ten FC428 isolates sporadically clustered into different phylogenetic clades, suggesting different introductions and local transmission of FC428. Two isolates showed close genetic relatedness to ceftriaxone-resistant clone A8806, which was only reported from Australia in 2013. Homologous recombination events were detected in penA between Neisseria gonorrhoeae and commensal Neisseria species (N. perflava and N. polysaccharea), providing evidence of commensal Neisseria species might serve as reservoirs of ceftriaxone resistance-mediating penA sequences in clinical gonococcal strains.

CONCLUSIONS

Our results demonstrate further dissemination of FC428 in China and resurgence risks of sporadic ceftriaxone-resistant A8806 to become the next clone to spread.

In Vitro Activity of Ertapenem against Neisseria gonorrhoeae Clinical Isolates with Decreased Susceptibility or Resistance to Extended-Spectrum Cephalosporins in Nanjing, China (2013 to 2019)

Neisseria gonorrhoeae isolates collected in Nanjing, China, that possessed decreased susceptibility (or resistance) to extended-spectrum cephalosporins (ESCs) were examined for susceptibility to ertapenem, and their sequence types were determined. Ceftriaxone and cefixime MICs of ≥0.125 mg/L and ≥0.25 mg/L, respectively, were first determined in 259 strains isolated between 2013 and 2019, and then MICs of ertapenem were measured using the antimicrobial gradient Epsilometer test (Etest). Also, genetic determinants of ESC resistance were identified and N. gonorrhoeae multiantigen sequence typing (NG-MAST) was performed to analyze associations with ertapenem susceptibility. All isolates displayed ertapenem MICs between 0.006 mg/L and 0.38 mg/L; the overall MIC₅₀ and MIC₉₀ were 0.032 mg/L and 0.125 mg/L, respectively. Forty-four (17.0%) isolates displayed ertapenem MICs of ≥0.125 mg/L; 10 (3.9%) had MICs of ≥0.25 mg/L. The proportion of isolates with ertapenem MICs of ≥0.125 mg/L increased from 4.0% in 2013 to 20.0% in 2019 (χ² = 24.144, P < 0.001; chi-square test for linear trend). The penA mosaic allele was present in a significantly higher proportion of isolates with ertapenem MICs of ≥0.125 mg/L than of isolates with MICs of ≤0.094 mg/L) (97.7% versus 34.9%, respectively; χ² = 58.158, P < 0.001). ST5308 was the most prevalent NG-MAST type (8.5%); ST5308 was also significantly more common among isolates with ertapenem MICs of ≥0.125 mg/L than isolates with MICs of ≤0.094 mg/L (22.7% and 5.6%, respectively; χ² = 13.815, P = 0.001). Ertapenem may be effective therapy for gonococcal isolates with decreased susceptibility or resistance to ESCs and isolates with identifiable genetic resistance determinants.

Evaluation of Neisseria gonorrhoeae Isolates Susceptibility to Tetracycline Antibiotics from 9 Provinces in China Since 2020

Purpose

Methods

Results

Conclusion

Pharmacodynamics of Ceftriaxone, Ertapenem, Fosfomycin and Gentamicin in Neisseria gonorrhoeae

Objectives: To assess the in vitro effect of select antimicrobials on the growth of N. gonorrhoeae and its pharmacodynamic parameters. Methods: Time–kill assays were performed on two reference N. gonorrhoeae strains (ceftriaxone-resistant WHO X and ceftriaxone-susceptible WHO F) and one clinical N. gonorrhoeae strain (ceftriaxone-susceptible CS03307). Time–kill curves were constructed for each strain by measuring bacterial growth rates at doubling antimicrobial concentrations of ceftriaxone, ertapenem, fosfomycin and gentamicin. Inputs from these curves were used to estimate minimal bacterial growth rates at high antimicrobial concentrations (ψ_min), maximum bacterial growth rates in the absence of antimicrobials (ψ_max), pharmacodynamic minimum inhibitory concentrations (zMIC), and Hill’s coefficients (κ). Results: Ceftriaxone, ertapenem and fosfomycin showed gradual death overtime at higher antimicrobial concentrations with a relatively high ψ_min, demonstrating time-dependent activity. Compared to WHO F, the ψ_min for WHO X was significantly increased, reflecting decreased killing activity for ceftriaxone, ertapenem and fosfomycin. At high ceftriaxone concentrations, WHO X was still efficiently killed. CS03307 also showed a high ψ_min for ceftriaxone in spite of a low MIC and no difference in ψ_min for fosfomycin in spite of significant MIC and zMIC differences. Gentamicin showed rapid killing for all three strains at high concentrations, demonstrating concentration-dependent activity. Conclusions: Based on time–kill assays, high-dosage ceftriaxone could be used to treat N. gonorrhoeae strains with MIC above breakpoint, with gentamicin as a potential alternative. Whether ertapenem or fosfomycin would be effective to treat strains with a high MIC to ceftriaxone is questionable.