TABLE 6.
Antimicrobial susceptibilities, pIs, and types of β-lactamases for E. coli and K. pneumoniae strains isolated from children with bloodstream infections at the Seoul National University Children's Hospital, 1993 to 1998a
| Group | No. of strains | pI value(s) of β-lactamase(s)b | β-Lactamase type(s) produced | MIC range/MIC50/MIC90 (μg/ml)c
|
|||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Ceftazidime | Cefotaxime | Aztreonam | Cefotetan | Piperacillin | Piperacillin- tazobactamd | Gentamicin | Amikacin | ||||
| E. coli | |||||||||||
| Ec-A | 7 | 5.4, 5.9 | TEM-1 + TEM-52 | 8-128/16/32 | 4-128/16/32 | 4-64/8/16 | 0.25-8/1/2 | 128->256/256/>256 | 1-2/1/2 | 0.5->256/128/>256 | 1-4/2/2 |
| Ec-B | 3 | 5.4, 7.6 | TEM-1 + SHV-2a | 1, 2, 8 | 2, 2, 16 | 0.5, 0.5, 4 | 0.12, 0.12, 0.25 | >256, 64, 128 | 1, 1, 4 | 8, 16, 256 | 4, 4, 8 |
| Ec-C | 2 | 5.4, 5.7, 5.9 | TEM-1 + PSE-1-like + TEM-52 | 16, 8 | 8, 4 | 4, 2 | 0.25, 1 | 256, 128 | 8, 2 | 64 | 16, 64 |
| Ec-D | 2 | 5.4, 5.7, 7.6, 8.0 | TEM-1 + TEM-88 + SHV-2a + CMY-1-like | 32, 16 | 64, >32 | 4, 8 | 256, >32 | >256, >128 | 64, 8 | 2 | 16 |
| Ec-E | 1 | 5.4, 5.9, 8.0 | TEM-1 + TEM-52 + CMY-1-like | 16 | 64 | 2 | 256 | >128 | 4 | >256 | 32, >32 |
| Ec-F | 1 | 7.6 | SHV-2a | 1 | 2 | 0.5 | 0.12 | 64 | 1 | 4 | 2 |
| K. pneumoniae | |||||||||||
| Kp-A | 12 | 5.4, 5.9 | TEM-1 + TEM-52 | 8-64/32/64 | 4-64/16/32 | 4-32/8/16 | 0.12-64/0.5/1 | 128->256/128/>256 | 0.5-4/2/4 | 8->128/128/128 | 1-84/2/32 |
| Kp-B | 10 | 7.6 | SHV-2a | 0.5-32/2/4 | 2-16/4/8 | 0.5-8/1/2 | 0.003-1/0.006/0.12 | 64->256/128/256 | 0.5-4/1/1 | 0.5->256/1/16 | 1-32/2/8 |
| Kp-C | 3 | 5.4, 7.6 | TEM-1 + SHV-2a | 8, 2, 8 | 8, 2, 16 | 4, 1, 4 | 0.12, 0.12, 1 | 128, 256, >256 | 8, 4, 1 | 4, 8, 64 | 1, 8, 32 |
| Kp-D | 3 | 5.4, 8.2 | TEM-1 + SHV-12 | 1, 64, 64 | 1, 8, 16 | 4, 32, 64 | 8, 0.25, 0.25 | 256, 128, 256 | 2, 1, 4 | 256, 128, 256 | 8, 16, 16 |
| Kp-E | 2 | 5.4, 5.9 | TEM-1 + TEM-15 | 8, 8 | 16, 4 | 4, 2 | 0.5, 0.5 | >256, >256 | 2, 2 | 128, 64 | 1 |
| Kp-F | 1 | 5.9, 7.6 | TEM-52 + SHV-2a | 32 | 16 | 16 | 0.5 | >256 | 0.5 | 8 | 8 |
| Kp-G | 1 | 5.4, 5.9, 7.4 | TEM-1 + TEM-52 + OXA-1-like | 256 | 256 | 128 | 8 | >256 | 64 | 256 | 16 |
| Kp-H | 1 | 5.4, 5.9, 8.0 | TEM-1 + TEM-52 + CMY-1-like | 64 | 128 | 16 | 256 | >256 | 64 | 64 | 16 |
| Kp-I | 1 | 5.4, 5.6 | TEM-1 + TEM-88 | 64 | 16 | 32 | 1 | >128 | 8 | 8 | 64 |
| Kp-J | 1 | 5.4, 8.0 | TEM-1 + CTX-M-14 | 1 | 32 | 2 | <0.06 | >128 | 0.5 | 0.25 | 1 |
| Kp-K | 1 | 5.4, 7.6, 8.0 | TEM-1 + SHV-2a + CTX-M-14 | 4 | 16 | 4 | 0.25 | 256 | 2 | 128 | 2 |
Among the 54 strains analyzed for ESBLs, 2 strains of E. coli that were considered AmpC hyperproducers were not included in the analysis for the data presented in this table.
In addition to the chromosomal SHV-type β-lactamase of K. pneumoniae.
MICs were determined by the agar dilution method. MIC50 and MIC90, MICs at which 50 and 90% of isolates tested are inhibited, respectively. The inhibitory concentration for each strain rather than the MIC range, MIC50, and MIC90 is shown for groups with less than four isolates.
Tazobactam was used at fixed concentration of 4 μg/ml, and the concentration of piperacillin is presented in the table.