Table 1.
Antimicrobial susceptibility of representative mutants selected after biocide exposure
| Selective biocide | Sub-culturea | MIC (mg/L)b |
||||||
|---|---|---|---|---|---|---|---|---|
| NAL | CIP | CHL | TET | KAN | TRI | |||
| Strain | ||||||||
| SL1344 | none | 8 | 2 | <0.015 | 1 | 0.5 | 4 | 0.06 |
| AQ1 | AQAS | 5 | 32 | 0.015 | 2 | 0.5 | 8 | 0.015 |
| AQ2 | AQAS | 6 | 32 | 0.06 | 64 | 4 | 4 | 0.5 |
| AQ4 | AQAS | 8 | 32 | 0.06 | 64 | 8 | 4 | 0.25 |
| AQ5 | AQAS | 8 | 16 | 0.03 | 32 | 4 | 4 | 1 |
| SK1 | Superkill | 2 | 32 | 0.12 | 64 | 8 | 2 | 0.5 |
| SK3 | Superkill | 5 | 32 | 0.12 | 64 | 8 | 4 | 0.5 |
| SK4 | Superkill | 6 | 16 | 0.06 | 16 | 4 | 4 | 1 |
| SK7 | Superkill | 7 | 4 | <0.015 | 4 | 1 | 4 | 4 |
| T2 | Trigene | 2 | 512 | 0.25 | 1 | 0.5 | 4 | >1024 |
| T3 | Trigene | 3 | 512 | 0.25 | 1 | 0.5 | 4 | >1024 |
| T6 | Trigene | 4 | 512 | 0.25 | 1 | 0.5 | 4 | >1024 |
| T9 | Trigene | 5 | 512 | 0.25 | 1 | 0.5 | 4 | >1024 |
| V2 | Virkon | 2 | 512 | 0.25 | 4 | 2 | 4 | 0.25 |
| V4 | Virkon | 4 | 8 | <0.015 | 4 | 2 | 4 | 32 |
| V6 | Virkon | 6 | 512 | 0.25 | 4 | 2 | 4 | 0.25 |
| V8 | Virkon | 8 | 16 | <0.015 | 8 | 2 | 2 | 32 |
| Site-directed mutants and complements | ||||||||
| SL1344-rpoA | NA | NA | 32 | 0.015 | 2 | 0.5 | 8 | 0.015 |
| SL1344-zur | NA | NA | 2 | <0.015 | 1 | 0.5 | 4 | 0.06 |
| T2-pBAD-zur | NA | NA | 512 | 0.25 | 1 | 0.5 | 4 | >1024 |
| AQ1-pBAD-rpoA | NA | NA | 2 | <0.015 | 1 | 0.5 | 4 | 0.06 |
| AQ2-pBAD-rpoA | NA | NA | 32 | 0.06 | 64 | 4 | 4 | 0.5 |
NAL, nalidixic acid; CIP, ciprofloxacin; CHL, chloramphenicol; TET, tetracycline; KAN, kanamycin; TRI, triclosan; NA, not applicable.
aNumber of biocide exposures after which each strain was recovered.
bValues in bold indicate MICs ≥8-fold higher compared with SL1344.