TABLE 5.
β-Lactam challenge-induced β-lactamase expression in Δslt and ΔnagZ mutantsa
| Treat- ment |
Gene | Bu278 |
Bu278 Δslt |
Bu278 ΔnagZ |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Untreated |
Treated |
Untreated |
Treated |
Untreated |
Treated |
||||||||
| Normalized fold mRNA expression ± SD |
P
value |
Normalized fold mRNA expression ± SD |
P
value |
Normalized fold mRNA expression ± SD |
P
value |
Normalized fold mRNA expression ± SD |
P
value |
Normalized fold mRNA expression ± SD |
P
value |
Normalized fold mRNA expression ± SD |
P
value |
||
| MEM | penA* | 1.00 ± 0.05 | NA | 0.90 ± 0.16 | 0.96 | 1.00 ± 0.11 | NA | 0.87 ± 0.08 | 0.82 | 1.00 ± 0.07 | NA | 0.92 ± 0.07 | 0.91 |
| penB | 1.00 ± 0.08 | NA | 61.33 ± 11.39 | <0.001 | 1.00 ± 0.12 | NA | 22.86 ± 2.87 | <0.001 | 1.00 ± 0.11 | NA | 28.52 ± 3.19 | <0.001 | |
| ampC | 1.00 ± 0.20 | NA | 14.66 ± 3.56 | <0.001 | 1.00 ± 0.15 | NA | 4.99 ± 0.75 | <0.001 | 1.00 ± 0.12 | NA | 21.37 ± 2.23 | <0.001 | |
| IMP | penA* | 1.00 ± 0.12 | NA | 0.94 ± 0.19 | 0.99 | 1.00 ± 0.10 | NA | 0.73 ± 0.09 | 0.38 | 1.00 ± 0.10 | NA | 0.87 ± 0.07 | 0.94 |
| penB | 1.00 ± 0.12 | NA | 274.45 ± 51.20 | <0.001 | 1.00 ± 0.10 | NA | 13.17 ± 1.56 | <0.001 | 1.00 ± 0.15 | NA | 58.61 ± 5.77 | <0.001 | |
| ampC | 1.00 ± 0.07 | NA | 61.76 ± 10.27 | <0.001 | 1.00 ± 0.08 | NA | 1.95 ± 0.20 | 0.003 | 1.00 ± 0.14 | NA | 54.14 ± 6.19 | <0.001 | |
| CAZ | penA* | 1.00 ± 0.10 | NA | 1.00 ± 0.17 | 0.99 | 1.00 ± 0.08 | NA | 0.90 ± 0.09 | 0.014 | 1.00 ± 0.08 | NA | 1.05 ± 0.09 | 0.26 |
| penB | 1.00 ± 0.22 | NA | 5.04 ± 1.26 | <0.001 | 1.00 ± 0.06 | NA | 1.15 ± 0.10 | <0.001 | 1.00 ± 0.10 | NA | 1.14 ± 0.10 | 0.005 | |
| ampC | 1.00 ± 0.17 | NA | 3.41 ± 0.71 | <0.001 | 1.00 ± 0.06 | NA | 0.94 ± 0.10 | 0.13 | 1.00 ± 0.12 | NA | 0.93 ± 0.11 | 0.16 | |
Cells of Bu278 (wild type) and its Δslt and ΔnagZ mutants were grown to log phase in LB medium. Equal portions of the cell cultures remained untreated or were treated with a subinhibitory concentration of 1 μg/ml IMP, MEM, or CAZ. Total RNA was isolated after an additional 1 h of incubation at 37°C. The penA*, penB, ampC, and oxa mRNA levels were determined by RT-qPCR. Standard deviations (SD) between three biological replicates are indicated. Two-way ANOVA and Sidak’s multiple-comparison test were used to determine the significance of the change in fold mRNA expression levels between treated (MEM, IPM, or CAZ) and untreated strains. P values of <0.05 were considered significant. NA, not applicable.