TABLE 1.
MICs of antibiotics for clinical isolates producing 16S rRNA methylases, their corresponding armA- and rmtB-positive transformants, and E. coli TOP10a
| Clinical isolate or transformantb | 16S rRNA methylase or/and ESBLs | MIC (μg/ml) ofc:
|
Plasmid size (kb) | Incompatibility group plasmid type | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| AMK | NET | GEN | TOB | CTX | CAZ | IMP | NOR | CIP | ||||
| E coli VOG | rmtB and blaCTX-M-14 | >256 | >256 | >256 | >256 | >32 | 6 | 0.19 | >256 | >32 | 80, 50 | |
| E. coli TOP10(pVOG1) | rmtBd | >256 | >256 | >256 | >256 | 0.047 | 0.38 | 0.19 | 0.032 | 0.003 | 80 | F |
| E. coli TOP10(pVOG2) | blaCTX-M-14e | 1.5 | 1.5 | 0.25 | 3 | >32 | 2 | 0.19 | <0.016 | <0.002 | 50 | NDf |
| E coli COP | armA and blaCTX-M-14 | >256 | >256 | >256 | >256 | >32 | 1 | 0.19 | >256 | >32 | 60, 38 | |
| E. coli TOP10(pCOP1) | armA | >256 | >256 | >256 | >256 | 0.047 | 0.38 | 0.19 | <0.016 | <0.002 | 60 | F |
| E. coli TOP10(pCOP2) | blaCTX-M-14 | 1 | 0.125 | 0.125 | 0.19 | 8 | 1 | 0.19 | <0.016 | <0.002 | 38 | I1 |
| E coli MEZ | armA and blaCTX-M-3 | >256 | >256 | >256 | >256 | >32 | 3 | 0.19 | >256 | >32 | 120 | |
| E. coli TOP10(pMEZ) | armA and blaCTX-M-3 | >256 | >256 | >256 | >256 | >32 | 3 | 0.19 | 0.016 | <0.002 | 120 | L/M |
| Enterobacter cloacae BEH | armA and blaCTX-M-3 | >256 | >256 | >256 | >256 | >32 | 16 | 0.19 | 1 | 0.19 | 130 | |
| E. coli TOP10(pBEH) | armA and blaCTX-M-3 | >256 | >256 | >256 | >256 | >32 | 8 | 0.19 | 0.016 | <0.002 | 130 | L/M |
| Klebsiella pneumoniae DU | armA and blaCTX-M-3 | >256 | >256 | >256 | >256 | >32 | 2 | 0.19 | 0.75 | 0.125 | 120 | |
| E. coli TOP10(pDU) | armA and blaCTX-M-3 | >256 | >256 | >256 | >256 | >32 | 2 | 0.19 | 0.016 | <0.002 | 120 | L/M |
| E. coli TOP10 | 1 | 0.25 | 0.25 | 0.38 | 0.047 | 0.38 | 0.19 | <0.016 | <0.002 | |||
MICs of antibiotics were determined by using the Etest technique according to the manufacturer's recommendations. Analysis of plasmid content in the armA- and rmtB-positive isolates and their transformants was performed by the Kieser technique (7). The incompatibility group of plasmids was determined as previously described (2).
All clinical isolates were also resistant to sulfonamides, trimethoprim, chloramphenicol, tetracycline, and rifampin.
Antibiotic-resistant marker abbreviations: AMK, amikacin; NET, netilmicin; GEN, gentamicin; TOB, tobramycin; CTX, cefotaxime; CAZ, ceftazidime; IMP, imipenem; NOR, norfloxacin; and CIP, ciprofloxacin.
MICs for E. coli TOP10 transformants harboring pVOG1 expressing RmtB, TEM-1, and QepA.
MICs for E. coli TOP10 transformants harboring pVOG2 expressing CTX-M-14 and AAC(6′)-Ib.
ND, not determined.