TABLE 3.
Characterization of the resistance mechanisms of PAO1 and PAOMS lineages evolved in the presence of ceftazidime, meropenem, or ciprofloxacin in each of three experiments
| Straina | Relative mRNA expression level by geneb |
OprD lossc | Resistance mutation(s)d | ||||
|---|---|---|---|---|---|---|---|
| ampC | mexB | mexD | mexF | mexY | |||
| PAO1.1-CAZ | 350 ± 180 | <2 | <5 | dacB (W273X) + ampD (M1T) | |||
| PAO1.2-CAZ | 32 ± 5 | <2 | <5 | dacB (G407D) + ampD (V101G) | |||
| PAO1.3-CAZ | 68 ± 31 | <2 | <5 | dacB (nt307Δ4) + ampD (V101G) | |||
| PAOMS.1-CAZ | 244 ± 90 | <2 | <5 | dacB (G420D) + ampC (V239A) | |||
| PAOMS.2-CAZ | 673 ± 237 | <2 | <5 | dacB (G366D) + ampC (V239A) | |||
| PAOMS.3-CAZ | 254 ± 144 | <2 | <5 | ampR (D135N) | |||
| PAO1.1-CIP | <5 | <2 | 633 ± 62 | <5 | <5 | nfxB (W115X) + gyrA (T83I) + parC (S87L) | |
| PAO1.2-CIP | <5 | <2 | 690 ± 92 | <5 | <5 | nfxB (nt59Δ1) + gyrA (E153K) | |
| PAO1.3-CIP | <5 | 11.6 ± 4.3 | <5 | <5 | <5 | mexR (R83H) + gyrA (T83I) + parC (S87L) | |
| PAOMS.1-CIP | <5 | <2 | 656 ± 69 | <5 | <5 | nfxB (L172P) + gyrA (T83I) + parC (E91K) | |
| PAOMS.2-CIP | <5 | <2 | 652 ± 96 | <5 | <5 | nfxB (R42H) + gyrA (T83I) + parC (S87L) + dacB (A299T) | |
| PAOMS.3-CIP | <5 | <2 | 544 ± 317 | <5 | <5 | nfxB (L26P) + gyrA (T83I) + parC (S87L) | |
| PAO1.1-MER | <5 | 6.0 ± 0.8 | <5 | <5 | + | oprD (A150X) + mexR (T130P) | |
| PAO1.2-MER | <5 | 5.3 ± 2.0 | <5 | <5 | + | oprD (nt1329InsG) + mexR (R63H) | |
| PAO1.3-MER | <5 | 6.5 ± 1.4 | <5 | <5 | + | oprD (nt109Δ681) + mexR (nt307Δ1) | |
| PAOMS.1-MER | <5 | 7.7 ± 0.3 | <5 | <5 | + | oprD (W277X) + nalD (L91P) + mexT (F172I) | |
| PAOMS.2-MER | <5 | 21.9 ± 9.9 | <5 | <5 | + | oprD (W65X) + mexR (R91C) | |
| PAOMS.3-MER | <5 | 17.0 ± 1.0 | <5 | <5 | + | oprD (nt635InsG) + mexR (G101R) + mexT (A179V) | |
PAO1 or PAOMS ceftazidime (CAZ)-, ciprofloxacin (CIP)-, and meropenem (MER)-resistant mutant derivatives.
Relative ampC, mexB, mexD, mexF, and mexY expression levels compared to that of wild-type PAO1. Previously described breakpoints (18) were applied for defining overexpression: ampC, mexD, mexF, and mexY, positive >10-fold compared to wild-type PAO1, negative <5-fold; mexB, positive >3-fold compared to wild-type PAO1, negative <2-fold.
Lack of expression of OprD, as evidenced by the analysis of outer membrane proteins (OMPs) through SDS-PAGE.
Mutations in genes known to affect ampC, mexB, mexD, mexF, and mexY expression, oprD, and QRDR of gyrA, gyrB, parC, and parE.