Epidemiological surveillance study of gonococcal infection in Northern Spain

Comparison of gradient diffusion and molecular methods using Allplex™ NG&DR assay (Seegene®) for macrolide and fluoroquinolone screening resistance in Neisseria gonorrhoeae

Antimicrobial resistance in Neisseria gonorrhoeae (NG) is increasing worldwide. Second-line treatments with macrolides or fluoroquinolones are an option for NG infections in some cases following the STI guideline recommendations. In our study, we compared the gradient diffusion test using EUCAST 2024 breakpoints with a new molecular method using the Allplex™ NG&DR assay (Seegene®) including A2059G/C2611 mutations (23S rRNA) associated with high/moderate-level macrolide resistance and S91F mutation (gyrA) relationship with fluoroquinolone resistance in NG isolates (n = 100). We calculated the sensitivity, specificity, and correlation of the molecular test for fluoroquinolone using the gradient diffusion as the reference method. In twenty-three strains was not detected any mutation associated with macrolides or fluoroquinolone resistance. No A2059G/C2611T mutations were detected, and the S91F mutations were detected in 77 out of the 100 isolates screened. Twenty-three NG isolates were reported to be resistant to azithromycin (ECOFF: >1 mg/L), and 78 NG isolates were resistant to ciprofloxacin (MIC: >0.06 mg/L). The molecular method showed a sensitivity of 96.1% and, a specificity of 90.9% for fluoroquinolone susceptibility, but the statistical analysis between the molecular test and gradient diffusion test was not statistically significant for fluoroquinolone resistance (p = 1). Statistical analysis was not performed for macrolides because of the absence of positive RT-PCR results. According to our data, Allplex™ assay cannot replace the gradient diffusion test for macrolide resistance. However, the assay could be used to test fluoroquinolone resistance in NG isolates as a replacement for phenotypic methods.

Genome-based epidemiology and antimicrobial resistance of Neisseria gonorrhoeae in Spain: A prospective multicentre study

BACKGROUND

Whole-genome sequencing (WGS) of Neisseria gonorrhoeae isolates combined with epidemiological and phenotypic data provides better understanding of population dynamics.

AIM

The objective of this study was to investigate the molecular epidemiology of N. gonorrhoeae isolates from three centres in Spain and determine associations of antimicrobial resistance.

METHODS

Genetic characterization was performed in 170 N. gonorrhoeae isolates. WGS was carried out with the HiSeq platform (Illumina). Genome assemblies were submitted to the PubMLST Neisseria database website to determine NG-MAST, MLST and NG-STAR. Antimicrobial resistance genes and point mutations were identified with PubMLST. Phylogenomic comparison was based on whole-genome single nucleotide polymorphism analysis.

RESULTS

Twenty-six MLST, 49 NG-MAST and 41 NG-STAR sequence types were detected, the most prevalent being MLST-ST9363 (27.1%), NG-MAST ST569 (12.4%) and NG-STAR ST193 (14.7%). Phylogenetic analysis identified 13 clusters comprising 69% of the isolates, with two of note: one involved cefixime-resistant isolates from Barcelona presenting a mosaic penA X and belonging to MLST-ST7363 and the other involved azithromycin-resistant isolates from Mallorca that possessed the C2611T mutation in the four 23S rRNA alleles belonging to MLST-ST1901.

CONCLUSION

The population of N. gonorrhoeae is quite heterogeneous in Spain. Our results agree with previous data published in Europe, albeit with some differences in distribution between regions. This study describes the circulation of two gonococcal populations with a specific resistance profile and sequence type in a specific geographic area. WGS is an effective tool for epidemiological surveillance of gonococcal infection and detection of resistance genes.

Penicillin-Binding Protein Occupancy Dataset for 18 β-Lactams and 4 β-Lactamase Inhibitors in Neisseria gonorrhoeae

The lack of effective first-line antibiotic treatments against Neisseria gonorrhoeae, and the worldwide dissemination of resistant strains, are the main drivers of a worsening global health crisis. β-lactam antibiotics have been the backbone of therapeutic armamentarium against gonococci. However, we are lacking critical insights to design rationally optimized therapies. In the present work, we generated the first PBP-binding data set on 18 currently available and clinically relevant β-lactams and 4 β-lactamase inhibitors in two N. gonorrhoeae ATCC type collection strains, 19424 and 49226 (PBP2 type XXII and A39T change in mtrR). PBP binding (IC50) was determined via the Bocillin FL binding assay in isolated membrane preparations. Three clusters of differential PBP IC50s were identified and were mostly consistent across both strains, but with quantitative differences. Carbapenems were coselective for PBP2 and PBP3 (0.01 to 0.03 mg/L). Third- and fourth-generation cephalosporins cefixime, cefotaxime, ceftazidime, cefepime, and ceftriaxone showed the lowest IC50 values for PBP2 (0.01 mg/L), whereas cefoxitin, ceftaroline, and ceftolozane required higher concentrations (0.04 to >2 mg/L). Aztreonam was selective for PBP2 in both strains (0.03 to 0.07 mg/L); amdinocillin bound this PBP at higher concentrations (1.33 to 2.94 mg/L). Penicillins specifically targeted PBP2 in strain ATCC 19424 (0.02 to 0.19 mg/L) and showed limited inhibition in strain ATCC 49226 (0.01 to >2 mg/L). Preferential PBP2 binding was observed by β-lactam-based β-lactamase inhibitors sulbactam and tazobactam (1.07 to 6.02 mg/L); meanwhile, diazabicyclooctane inhibitors relebactam and avibactam were selective for PBP3 (1.27 to 5.40 mg/L). This data set will set the bar for future studies that will help the rational use and translational development of antibiotics against multidrug-resistant (MDR) N. gonorrhoeae. IMPORTANCE The manuscript represents the first N. gonorrhoeae PBP-binding data set for 22 chemically different drugs in two type strains with different genetic background. We have identified three clusters of drugs according to their PBP binding IC50s and highlighted the binding differences across the two strains studied. With the currently available genomic information and the PBP-binding data, we have been able to correlate the target attainment differences and the mutations that affect the drug uptake with the MIC changes. The results of the current work will allow us to develop molecular tools of great practical use for the study and the design of new rationally designed therapies capable of combating the growing MDR gonococci threat.

A Single Amino Acid Substitution in Elongation Factor G Can Confer Low-Level Gentamicin Resistance in Neisseria gonorrhoeae

The continued emergence of Neisseria gonorrhoeae isolates which are resistant to first-line antibiotics has reinvigorated interest in alternative therapies such as expanded use of gentamicin (Gen). We hypothesized that expanded use of Gen promotes emergence of gonococci with clinical resistance to this aminoglycoside. To understand how decreased susceptibility of gonococci to Gen might develop, we selected spontaneous low-level Gen-resistant (Gen^R) mutants (Gen MIC = 32 μg/mL) of the Gen-susceptible strain FA19. Consequently, we identified a novel missense mutation in fusA, which encodes elongation factor G (EF-G), causing an alanine (A) to valine (V) substitution at amino acid position 563 in domain IV of EF-G; the mutant allele was termed fusA2. Transformation analysis showed that fusA2 could increase the Gen MIC by 4-fold. While possession of fusA2 did not impair either in vitro gonococcal growth or protein synthesis, it did result in a fitness defect during experimental infection of the lower genital tract in female mice. Through bioinformatic analysis of whole-genome sequences of 10,634 international gonococcal clinical isolates, other fusA alleles were frequently detected, but genetic studies revealed that they could not decrease Gen susceptibility in a similar manner to fusA2. In contrast to these diverse international fusA alleles, the fusA2-encoded A563V substitution was detected in only a single gonococcal clinical isolate. We hypothesize that the rare occurrence of fusA2 in N. gonorrhoeae clinical isolates is likely due to a fitness cost during infection, but compensatory mutations which alleviate this fitness cost could emerge and promote Gen^R in global strains.

Large Increase in Azithromycin-Resistant Neisseria gonorrhoeae in Northern Spain

The aim of this study was to characterize the evolution of gonorrhea in the general population by correlating epidemiological, genotypic, and antimicrobial resistance data of Neisseria gonorrhoeae isolates collected in northern Spain from 2014 to 2018. One hundred ninety-four strains underwent antimicrobial susceptibility testing and were genetically analyzed by N. gonorrhoeae multiantigen sequence typing. Increasing cases of gonococcal infections have been observed after 2015. Most occurred in male with urethritis. Sequence type (ST)-9972 and ST-1576, the predominant genotypes identified, have not been previously described as epidemic clones. Of great concern was the significant increase in azithromycin-resistant N. gonorrhoeae. More than 30% of these isolates were obtained from men who have sex with men (MSM). ST-12302 was the most prevalent clone among the azithromycin-resistant strains, and was also resistant to penicillin, ciprofloxacin, and tetracycline. This multidrug-resistant clone was exclusively isolated from MSM during 2018. The incidence rates of gonorrhea and azithromycin-resistant N. gonorrhoeae have significantly increased due to the emergence of new clones. ST-12302 has recently been recognized as an epidemic clone; therefore, its surveillance could be the key in controlling further dissemination of azithromycin resistance. These data highlight the need to perform local studies to update treatment guidelines and reinforce preventive measures against gonorrhea.

Cyr SB, Pham CD, Kirkcaldy RD. Sustained Transmission of Neisseria gonorrhoeae with High-Level Resistance to Azithromycin, in Indianapolis, Indiana, 2017–2018

Background

Since 2014, Neisseria gonorrhoeae azithromycin (AZM) susceptibility has declined in the United States, but high-level AZM resistance (HL-AZMR) has been infrequent and sporadic. We describe a cluster of 14 N. gonorrhoeae isolates with HL-AZMR identified in Indianapolis over 13 months.

Methods

N. gonorrhoeae culture specimens (genital and extragenital) were collected from attendees of the Bell Flower Clinic. Isolates underwent antimicrobial susceptibility testing (AST) using Etest. AZM minimum inhibitory concentrations ≥256 µg/mL were classified as HL-AZMR. Local disease intervention specialists interviewed patients whose isolates demonstrated HL-AZMR and conducted partner services. Relatedness of isolates was investigated by genomic analyses.

Results

During 2017–2018, AST was performed in 1016 N. gonorrhoeae isolates collected at the Bell Flower Clinic. Fourteen isolates (1.4%) from 12 men collected over 13 months demonstrated HL-AZMR; all were cephalosporin susceptible. Of the 12 men, 9 were white and reported male sex partners. Nine of the men were able to be retested; all were cured with 250-mg ceftriaxone plus 1-g AZM. Two men named each other as partners; no other partners in common were reported. Genomic analysis demonstrated close relatedness of the HL-AZMR isolates and a novel combination of a mosaic-mtrR promoter along with 23S ribosomal RNA mutations that appear to have emerged from circulating strains.

Conclusions

The close genetic relatedness with limited epidemiologic linkages between patients highlights the challenges of gonorrhea partner investigations and suggests undetected local transmission. Local AST, rapid public health action, and epidemiologic investigations combined with genomic analysis provides a multipronged approach to understanding an outbreak of sexually transmitted disease.