Table 4.
Relationship between ciprofloxacin MIC, point mutations within the QRDRs of DNA gyrase and topoisomerase IV subunit genes and PMQR genes in 114 NAR iNTS isolates
| CIP MIC (mg/L) | No. of isolates | Amino acid change in GyrA | Amino acid change in ParC | Amino acid change in ParE | No. (%) Multiple mutations ratea | No. (%) Mutation rateb | No. (%) PMQR genes ratec |
|---|---|---|---|---|---|---|---|
| 0-0.125 | 47 | Asp87→Tyr [26], Asp87→Asn [12], Asp87→Gly [5], Ser83→Tyr [4] | 47 (100) | 25 (53.2) | |||
| 0.25–0.5 | 40 | Ser83→Tyr[15], Asp87→Gly [8], Asp87→Asn [6], Asp87→Tyr [5], Ser83→Phe [1] | Thr57→Ser [24], Ser80→Arg [8], Gly78→Cys [1] | 23 (57.5) | 40 (100) | 29 (72.5) | |
| 1–2 | 21 | Ser83→Tyr [14], Asp87→Gly [2], Asp87→Tyr [2], Asp87→Asn [1] | Thr57→Ser [19], Gly78→Cys [6], Ser80→Arg [1] | 19 (90.5) | 19 (90.5) | 10 (47.6) | |
| ≥4 | 6 | Ser83→Tyr [3], Ser83→Phe [3], Asp87→Asn [3], Asp87→Gly [3] | Thr57→Ser [6], Ser80→Arg [3], Ser80→Ile [3] | Asp530→Asn [2], Ala538→Thr [3], Ser458→Pro [1] | 6 (100) | 6 (100) | 3 (50) |
Notes: Alterations in the QRDRs of gyrB were not found in any of the isolates tested. The a indicates that isolates exhibit at least two mutations in the QRDRs. The b indicates that isolates exhibit one mutation in the QRDRs. The c indicates that isolates exhibit both mutations in the QRDRs and PMQR gene.
Abbreviations: CIP, ciprofloxacin; MIC, minimum inhibitory concentration.