Table 1

MICs of ertapenem and ceftriaxone, and presence of determinants of resistance to extended-spectrum cephalosporins, for N. gonorrhoeae clinical isolates (n = 257) and international reference strains (n = 17)

Cephalosporin resistance mechanism(s)No. (%) of isolates with MIC (μg/ml) ofa:
≤0.0020.0040.0080.0160.0320.0640.1250.250.5124
penA mosaicb isolates (n = 101)
    penA mosaicb + mtrRcTX3 (1.1)1 (0.4)
ETP2 (0.7)2 (0.7)
    penA mosaicb + penBdTX2 (0.7)
ETP2 (0.7)
    penA mosaicb + mtrRc + penBdTX2 (0.7)6 (2.2)22 (8.0)28 (10)30 (11)3 (1.1)1 (0.4)1 (0.4)2 (0.7)
ETP1 (0.4)3 (1.1)3 (1.1)23 (8.4)44 (16)21 (7.7)
penA A501-altered isolates (n = 70)
    penA A501VeTX1 (0.4)
ETP1 (0.4)
    penA A501Ve + mtrRcTX1 (0.4)
ETP1 (0.4)
    penA A501Ve + penBdTX3 (1.1)
ETP1 (0.4)2 (0.7)
    penA A501V/Te + mtrRc + penBdTX1 (0.4)3 (1.1)11 (4.0)33 (12)17 (6.2)
ETP1 (0.4)11 (4.0)17 (6.2)16 (5.8)19 (6.9)1 (0.4)
Isolates with other penA (n = 103)
    mtrRc + penBdTX2 (0.7)8 (2.9)5 (1.8)13 (4.7)30 (11)14 (5.1)1 (0.4)
ETP13 (4.7)9 (3.3)23 (8.4)27 (9.8)1 (0.4)
    mtrRcTX1 (0.4)3 (1.1)
ETP1 (0.4)1 (0.4)2 (0.7)
    penBdTX4 (1.4)4 (1.4)1 (0.4)2 (0.7)
ETP1 (0.4)3 (1.1)4 (1.4)2 (0.7)1 (0.4)
    Wild typeTX5 (1.8)6 (2.2)1 (0.4)1 (0.4)1 (0.4)1 (0.4)
ETP1 (0.4)5 (1.8)5 (1.8)2 (0.7)2 (0.7)
TotalTX11 (3.9)20 (7.3)15 (5.5)25 (9.1)71 (30)77 (28)48 (18)3 (1.1)1 (0.4)1 (0.4)2 (0.7)
ETP2 (0.8)10 (3.7)37 (14)36 (13)70 (25)95 (34)23 (8.5)
  • a Only whole MIC dilutions are presented. TX, ceftriaxone; ETP, ertapenem.

  • b penA mosaic, mosaic alleles, which may differ in their exact nucleotide sequences, encoding a mosaic penicillin binding protein 2 (PBP2), which causes decreased susceptibility to extended-spectrum cephalosporins.

  • c Characteristic single nucleotide (A) deletion in the inverted repeat of the promoter region of mtrR that causes overexpression of the MtrCDE efflux pump, which results in a further decreased susceptibility to extended-spectrum cephalosporins.

  • d Alterations of amino acids 120 and/or 121 in the porin PorB1b that cause a decreased intake of extended-spectrum cephalosporins and, accordingly, a further decreased susceptibility to extended-spectrum cephalosporins.

  • e Alterations of amino acid A501 in PBP2, which has been associated with decreased susceptibility to extended-spectrum cephalosporins.