TABLE 1.
Antibiotic susceptibility of lasR and fusA1 G61A mutant strains
| Antibiotic susceptibilitya,b |
|||||
|---|---|---|---|---|---|
| Strain | Cipro | Imi | Tet | Pip | Ceft |
| PA14 | 0.09 (0.01) | 0.7 (0.1) | 5 (2) | 50 | 49 (2) |
| PA14 ΔlasR | 0.08 (0.01) | 0.8 (0.1) | 5 (2) | 50 | 11 (5)**** |
| fusA1 G61A | 0.06 | 0.8 (0.1) | 6 (2) | 50 | 13 |
| fusA1 G61A ΔlasR | 0.12 (0.03)**c | 0.8 (0.2) | 4 (2) | 50 | 10 (2) |
Antibiotic susceptibility was determined by MIC as described in Materials and Methods. Cipro, ciprofloxacin; Imi, imipenem; Tet, tetracycline; Pip, piperacillin; Ceft, ceftazidime. The values represent the average of three independent MIC experiments with the standard deviation in parentheses. Standard deviation was zero where not indicated.
The significance of the effects of fusA1 (wild-type fusA1 in PA14 or G61A) and lasR allele (intact lasR or ΔlasR) and the interaction of the two on MIC was determined by two-way ANOVA. The interaction was significant for ciprofloxacin (P < 0.01 and F1,8 = 13.98) and for ceftazidime (P < 0.0001 and F1,8 = 91.16). There was no significance of interaction (P > 0.05) for imipenem, tetracycline, and piperacillin.
Superscripted asterisks indicate the significance of comparing LasR+ and LasR− of each strain (PA14 or fusA1 G61A) using Sidak’s post hoc analysis with P values adjusted for multiple comparisons of all strains. There was no significance (P > 0.05) unless indicated. **, P < 0.01; ****, P < 0.0001.