Neisseria gonorrhoeae Sequence Typing for Antimicrobial Resistance, a Novel Antimicrobial Resistance Multilocus Typing Scheme for Tracking Global Dissemination of N. gonorrhoeae Strains

Abstract

A curated Web-based user-friendly sequence typing tool based on antimicrobial resistance determinants in <i>Neisseria gonorrhoeae</i> was developed and is publicly accessible (https://ngstar.canada.ca). The <i>N. gonorrhoeae</i> Sequence Typing for Antimicrobial Resistance (NG-STAR) molecular typing scheme uses the DNA sequences of 7 genes (<i>penA</i>, <i>mtrR</i>, <i>porB</i>, <i>ponA</i>, <i>gyrA</i>, <i>parC</i>, and 23S rRNA) associated with resistance to β-lactam antimicrobials, macrolides, or fluoroquinolones. NG-STAR uses the entire <i>penA</i> sequence, combining the historical nomenclature for <i>penA</i> types I to XXXVIII with novel nucleotide sequence designations; the full <i>mtrR</i> sequence and a portion of its promoter region; portions of <i>ponA</i>, <i>porB</i>, <i>gyrA</i>, and <i>parC</i>; and 23S rRNA sequences. NG-STAR grouped 768 isolates into 139 sequence types (STs) (<i>n</i> = 660) consisting of 29 clonal complexes (CCs) having a maximum of a single-locus variation, and 76 NG-STAR STs (<i>n</i> = 109) were identified as unrelated singletons. NG-STAR had a high Simpson's diversity index value of 96.5% (95% confidence interval [CI] = 0.959 to 0.969). The most common STs were NG-STAR ST-90 (<i>n</i> = 100; 13.0%), ST-42 and ST-91 (<i>n</i> = 45; 5.9%), ST-64 (<i>n</i> = 44; 5.72%), and ST-139 (<i>n</i> = 42; 5.5%). Decreased susceptibility to azithromycin was associated with NG-STAR ST-58, ST-61, ST-64, ST-79, ST-91, and ST-139 (<i>n</i> = 156; 92.3%); decreased susceptibility to cephalosporins was associated with NG-STAR ST-90, ST-91, and ST-97 (<i>n</i> = 162; 94.2%); and ciprofloxacin resistance was associated with NG-STAR ST-26, ST-90, ST-91, ST-97, ST-150, and ST-158 (<i>n</i> = 196; 98.0%). All isolates of NG-STAR ST-42, ST-43, ST-63, ST-81, and ST-160 (<i>n</i> = 106) were susceptible to all four antimicrobials. The standardization of nomenclature associated with antimicrobial resistance determinants through an internationally available database will facilitate the monitoring of the global dissemination of antimicrobial-resistant <i>N. gonorrhoeae</i> strains.