TABLE 2.
MICs of strains selected stepwise for reduced susceptibility to norfloxacin
| Lineage and strain (step no.)b | MIC (μg/ml)a
|
|||||
|---|---|---|---|---|---|---|
| NOR | CIP | NAL | TET | CHL | MEC | |
| Parent (Nu14) | 0.064 | 0.016 | 1.5 | 0.75 | 3 | 0.064 |
| Lineage 1 | ||||||
| Nu118 (1) | 0.25 | 0.094 | 16 | 0.5 | 2 | 0.064 |
| PL668 (2) | 1 | 0.25 | 16 | 0.75 | 8 | 0.094 |
| PL3637 (3) | 2 | 0.38 | 24 | 0.25 | 1.5 | 0.032 |
| PL3622 (3) | 3 | 0.5 | 64 | 0.75 | 4 | 0.125 |
| PL2090 (3) | 1.5 | 0.38 | 256 | 1 | 6 | 0.25 |
| PL2055 (3) | 1.5 | 0.38 | 256 | 1 | 6 | 0.25 |
| PL787 (2) | 0.5 | 0.125 | 32 | 1 | 8 | 0.064 |
| PL3665 (3) | 1 | 0.25 | 32 | 1.5 | 8 | 0.094 |
| PL3687 (3) | 1 | 0.19 | 32 | 1.5 | 8 | 0.094 |
| Lineage 2 | ||||||
| Nu41 (1) | 0.5 | 0.19 | 96 | 0.75 | 4 | 0.047 |
| PL213 (2) | 1.5 | 0.5 | >256 | 0.5 | 4 | 0.064 |
| PL1660 (3) | 6 | 2 | >256 | 0.75 | 8 | 0.125 |
| PL1965 (4) | 16 | 3 | >256 | 1 | 24 | 0.19 |
| PL3511 (5) | 64 | 8 | >256 | 0.75 | 48 | 0.38 |
| PL3515 (5) | 32 | 3 | >256 | 0.75 | 16 | 0.125 |
| PL1710 (3) | 8 | 4 | >256 | 0.75 | 3 | 0.064 |
| Lineage 3 | ||||||
| Nu71 (1) | 0.5 | 0.094 | 6 | 0.75 | 4 | 0.047 |
| PL136 (2) | 1.5 | 0.38 | 8 | 1 | 12 | 0.094 |
| PL3543 (3) | 2 | 0.38 | 12 | 1 | 12 | 0.5 |
| PL3547 (3) | 3 | 0.5 | 8 | 1 | 12 | 0.094 |
| Lineage 4 | ||||||
| Nu17 (1) | 0.25 | 0.064 | 3 | 0.75 | 4 | 0.064 |
| PL490 (2) | 0.75 | 0.094 | 3 | 0.38 | 2 | 0.094 |
| PL1270 (3) | 1 | 0.25 | 64 | 0.38 | 3 | 0.064 |
| PL3563 (4) | 4 | 0.75 | >256 | 1 | 24 | 0.125 |
| Lineage 5 | ||||||
| Nu18 (1) | 0.38 | 0.064 | 3 | 2 | 24 | 0.125 |
| PL845 (2) | 2 | 0.38 | >256 | 3 | 24 | 0.125 |
| PL1773 (3) | 3 | 0.75 | >256 | 1.5 | 12 | 0.094 |
| PL1801 (3) | 4 | 1 | >256 | 2 | 64 | 4 |
| PL1900 (3) | 3 | 0.5 | >256 | 2 | 24 | 0.094 |
| PL3425 (4) | 4 | 0.75 | >256 | 2 | 32 | 0.094 |
| PL3460 (4) | 16 | 1.5 | >256 | 2 | 16 | 0.125 |
| PL858 (2) | 0.75 | 0.125 | 6 | 2 | 32 | 0.5 |
| PL1385 (3) | 4 | 1.5 | >256 | 2 | 24 | 0.5 |
| PL2113 (4) | 12 | 3 | >256 | 2 | 16 | 0.38 |
| PL2127 (4) | 16 | 4 | >256 | 1.5 | 12 | 0.38 |
| Lineage 6 | ||||||
| Nu135 (1) | 0.19 | 0.047 | 3 | 1.5 | 8 | 0.094 |
| PL923 (2) | 1 | 0.25 | >256 | 1 | 8 | 0.094 |
| PL1570 (3) | 1.5 | 0.38 | >256 | 1 | 6 | 0.064 |
| PL1645 (3) | 3 | 0.5 | >256 | 0.75 | 1.5 | 1 |
a
The MIC for trimethoprim was also measured for all selected strains and showed no significant variation as a function of selection from the value in the starting strain Nu14 (trimethoprim MIC, 0.5). See footnote b of Table 1 for definitions of the abbreviations.
b
The selection step at which a particular mutant was isolated is provided in parentheses.