Figure 2. Comparison of GyrA quinolone-resistance–determining region (QRDR) for the alteration of amino acids in Neisseria meningitidis isolates. GyrA QRDR 1, ciprofloxacin-sensitive strains RRL-1, RRL-2, SFDJ 723, Ap-II 420; GyrA QRDR 2, ciprofloxacin-resistant strains SFDJ E-100, SFDJ E-79, SFDJ E-63, NICD 18, SFDJ E-95, IR-I 442; GyrA QRDR 3, ciprofloxacin-resistant strain IR-II 440. Ciprofloxacin-sensitive RRL-1 and RRL-2 were the reference strains, and the other 9 strains were from the outbreak. The shaded positions of the amino acids denote changes in GyrA QRDR of ciprofloxacin-resistant N. meningitidis in Thr-91 → Ile, Asn-103 → Asp, Ile-111 → Val, and Val-120 → Ile. The mutation of amino acid at conservative position 91 (Thr-91 → Ile) is responsible for the decreased susceptibility to fluoroquinolones, and the other 3 changes are synonymous.