Objectives: To ascertain whether the antimicrobial susceptibility of Neisseria gonorrhoeae isolates with differing susceptibilities to penicillin is associated with genogroups (GGs) and combined mutation patterns in PBP2 (penA), the multiple transfer resistance repressor (MtrR; mtrR) and porin B (PorB; porB).
Methods: The susceptibility of 146 clinical N. gonorrhoeae isolates to penicillin was determined using the agar dilution method and the interpretation criteria of CLSI. The DNA sequences of penA, mtrR and porB in isolates were compared with WT sequences and mutation patterns were determined. Isolates were typed by N. gonorrhoeae multi-antigen sequence typing (NG-MAST) and STs were grouped into specific GGs.
Results: The isolates tested carried 9 mutation patterns in PBP2 and 12 mutation patterns in each of MtrR and PorB. Of the 146 isolates, 121 (82.9%) were grouped into 13 different GGs. Isolates with penicillin MICs of 0.03-0.06 mg/L were significantly associated with GG25 (P < 0.05) and PBP2/MtrR/PorB mutation pattern I/WT/WT (P < 0.01). Isolates with a penicillin MIC of 1.0 mg/L were associated (P < 0.05) with: (i) GG3655 and mutation pattern XXII/A-;G45D/G120K;A121N; (ii) GG921 and mutation pattern IX/G45D/G120D;A121N; and (iii) GG1109 and mutation pattern IX/G45D/WT. Sixty percent (9/15) of penicillin-resistant isolates (MIC ≥2 mg/L) were GG3654 (P < 0.0001) and carried mutation pattern IX/G45D/G120K;A121D or IX/G45D/G120D;A121D (P < 0.05).
Conclusions: Specific mutation patterns in PBP2/MtrR/PorB were associated with specific GGs and penicillin susceptibility. This approach of typing strains and resistance patterns is ideal for predicting antimicrobial resistance and should be used in instances in which gonococcal culture is not available but DNA can be obtained from clinical specimens.