Table 1. Distribution of PMQR genes in E. coli phylogenetic groups and the corresponding fluoroquinolone minimal inhibitory concentration (MIC) ranges.
| PMQR genes | N | Phylogenetic group (N, %) | Ciprofloxacin (μg/mL) | Levofloxacin (μg/mL) | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| A | B1 | B2 | D | MIC range | MIC50 | MIC90 | MIC range | MIC50 | MIC90 | ||
| qnrS1 | 38 | 25 (65.8) | 9 (23.7) | 4 (10.5) | 0 | 1–64 | 4 | 32 | 1–128 | 4 | 32 |
| aac(6′)Ib-cr | 33 | 16 (48.5) | 6 (18.2) | 3 (9.1) | 8 (24.2) | 1–256 | 32 | 128 | 2–64 | 8 | 32 |
| oqxA+oqxB | 32 | 18 (56.3) | 10 (31.3) | 0 | 4 (12.5) | 1–64 | 8 | 32 | 1–32 | 8 | 16 |
| qnrS1+oqxA+oqxB | 6 | 3 (50) | 3 (50) | 0 | 0 | 1–8 | 2 | 8 | 1–32 | 4 | 32 |
| aac(6′)Ib-cr+oqxA+oqxB | 4 | 2 (50) | 2 (50) | 0 | 0 | 8–32 | 16 | 32 | 16–32 | 16 | 32 |
| qnrS1+aac(6′)Ib-cr | 2 | 2 (100) | 0 | 0 | 0 | - | - | - | - | - | - |
| qnrB1+aac(6′)Ib-cr | 2 | 2 (100) | 0 | 0 | 0 | - | - | - | - | - | - |
| oqxA | 1 | 0 | 0 | 0 | 1 | - | - | - | - | - | - |
| qnrS1+qnrB1+aac(6′)Ib-cr | 1 | 1 | 0 | 0 | 0 | - | - | - | - | - | - |
| qnrB1+aac(6′)Ib-cr+oqxA+oqxB | 1 | 1 | 0 | 0 | 0 | - | - | - | - | - | - |
| Total | 120 | 70 (58.3) | 30 (25.0) | 7 (5.8) | 13 (16.7) | ||||||
Abbreviations: MIC50, minimum inhibitory concentration required to kill 50% of the microbial population; MIC90, minimum inhibitory concentration required to kill 90% of the microbial population.