TABLE 2.
Reference susceptibility testing result and interpretive category according to NCCLS criteriaa
| Strain | Characteristic(s) | MIC (μg/ml) ofb:
|
||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| P/T | FOX | CTX | CRO | CAZ | FEP | ATM | IMP | MER | ||
| E. coli ATCC 25922 | ATCC QC | 2/4 (S) | 2 (S) | 0.06 (S) | 0.06 (S) | 0.25 (S) | 0.03 (S) | 0.12 (S) | 0.12 (S) | ≤0.01 (S) |
| E. coli HUS 31-94 | AmpC ↑c + OmpF− | 64/4 (I) | >256 (R) | 16 (I) | 16 (I) | 256 (R) | 1 (S) | 32 (R) | 0.25 (S) | ≤0.01 (S) |
| K. pneumoniae JCH1 | SHV-1 ↑ | 16/4 (S) | 2 (S) | 0.25 (S) | 0.25 (S) | 1 (S) | 0.12 (S) | 0.25 (S) | 0.06 (S) | ≤0.01 (S) |
| E. coli RYC9765550 | OXA-1 | 32/4 (I) | 2 (S) | 0.25 (S) | 0.12 (S) | 0.5 (S) | 1 (S) | 0.12 (S) | 0.12 (S) | ≤0.01 (S) |
| E. coli RYC5H/9 | TEM-27 + TEM-1 | 1/4 (S) | 2 (S) | 0.5 (R) | 0.5 (R) | >512 (R) | 1 (R) | 256 (R) | 0.12 (S) | ≤0.01 (S) |
| E. coli RYC97056888 | CTX-M-9 + TEM-1 | 1/4 (S) | 2 (S) | 8 (R) | 16 (R) | 0.5 (R) | 4 (R) | 1 (R) | 0.06 (S) | ≤0.01 (S) |
| K. oxytoca RYC9147/8 | K1 | 128/4 (R) | 2 (S) | 0.12 (S) | 1 (S) | 0.12 (S) | 0.06 (S) | 4 (S) | 0.06 (S) | ≤0.01 (S) |
| K. pneumoniae LB3 | SHV-5 + OmpK35− | 8/4 (S) | 2 (S) | 8 (R) | 4 (R) | 128 (R) | 1 (R) | 128 (R) | 0.06 (S) | ≤0.01 (S) |
| K. pneumoniae LB4 | SHV-5 + Omp35−/36− | 512/4 (R) | 64 (R) | 128 (R) | 64 (R) | >512 (R) | 32 (R) | 512 (R) | 0.12 (S) | 0.06 (S) |
| E. cloacae RYC11439/9 I | AmpC | 1/4 (S) | NA | 0.25 (S) | 0.25 (S) | 0.25 (S) | 0.06 (S) | 0.06 (S) | 0.12 (S) | 0.03 (S) |
| E. cloacae RYC11439/9 SDM | AmpC ↑ | 256/4 (R) | NA | >256 (R) | >256 (R) | 256 (R) | 4 (S) | 128 (R) | 0.12 (S) | 0.06 (S) |
| E. cloacae RYC97095983 I | AmpC + CTX-M-10 | 1/4 (S) | NA | 64 (R) | 64 (R) | 2 (S)d | 8 (S)d | 16 (I)d | 0.12 (S) | 0.03 (S) |
| E. cloacae RYC97095983 SDM | AmpC ↑ + CTX-M-10 | 64/4 (I) | NA | 256 (R) | 256 (R) | 64 (R) | 32 (R) | 64 (R) | 0.12 (S) | 0.06 (S) |
| P. aeruginosa ATCC 27853 | ATCC QC | 2/4 (S) | NA | NA | NA | 2 (S) | 2 (S) | 4 (S) | 2 (S) | 0.25 (S) |
| P. aeruginosa HUS C28 | AmpC ↑ | 256/4 (R) | NA | NA | NA | 256 (R) | 16 (1) | 64 (R) | 1 (S) | 0.25 (S) |
| P. aeruginosa PAO1 OprD- | AmpC + OprD− | 1/4 (S) | NA | NA | NA | 1 (S) | 1 (S) | 2 (S) | 16 (R) | 2 (S) |
| P. aeruginosa HUS3 MUT3 | AmpC ↑ + OprD− | 512/4 (R) | NA | NA | NA | 32 (R) | 8 (S) | 16 (I) | 16 (R) | 4 (S) |
| P. aeruginosa HUSC9 | AmpC + MexABOprM | 8/4 (S) | NA | NA | NA | 32 (R) | 8 (S) | 16 (I) | 2 (S) | 4 (S) |
a
NCCLS interpretive criteria are given in reference 24.
b
P/T, piperacillin-tazobactam; CTX, cefotaxime; CRO, ceftriaxone; CAZ, ceftazidime; FEP, cefepime; ATM, aztreonam; IMP, imipenem; MER, meropenem; S, susceptible; I, intermediate; R, resistant; NA, not applicable.
c
↑, hyperproduction.
d
The presence of an ESBL in these isolates led reference laboratories to consider cephalosporins and aztreonam as resistant; however, interpretation of results has been performed considering the indicated interpretive categories according to NCCLS criteria (24).