TABLE 4.
Overview of MIC results of the Accelerate Pheno system and the Etests in isolates resistant to piperacillin-tazobactam, ceftriaxone, ertapenem, or meropenema
| Isolate (n = 13) | Testb | MIC (μg/ml)c |
Comment | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| SAM | TZP | FEP | CRO | ETP | MEM | AMK | GEN | TOB | CIP | CST | |||
| C. freundii (1) | ACC | – | 128 (R) | ≤1 (S) | ≥8 (R) | 0.25 (S) | ≤0.25 (S) | ≤4 (S) | ≤1 (S) | ≤1 (S) | ≤0.25 (S) | ≤0.5 (S) | AmpC positive |
| Etest | ND | >256 (R) | 1 (S) | >32 (R) | 0.094 (S) | 0.047 (S) | 1.5 (S) | 0.25 (S) | 1 (S) | 0.047 (S) | 1.5 (S) | ||
| E. coli (2) | ACC | 4 (S) | ≤4 (S) | ≤1 (S) | ≥8 (R) | 0.25 (S) | ≤0.25 (S) | ≤4 (S) | ≤1 (S) | ≤1 (S) | ≤0.25 (S) | ≤0.5 (S) | ESBL positive |
| Etest | 6 (S) | 0.75 (S) | * | >32 (R) | 0.012 (S) | 0.032 (S) | 2 (S) | 0.5 (S) | 0.75 (S) | 0.5 (S) | 1 (S) | ||
| E. coli (3) | ACC | ≥64 (R) | ≤4 (S) | 16 (R) | ≥8 (R) | ≤0.125 (S) | ≤0.25 (S) | ≤4 (S) | 16 (R) | 16 (R) | ≥8 (R) | ≤0.5 (S) | ESBL positive |
| Etest | 24 (R) | 2 (S) | * | >32 (R) | 0.012 (S) | 0.023 (S) | 4 (S) | 24 (R) | 24 (R) | >32 (R) | 0.75 (S) | ||
| E. coli (4) | ACC | ≥64 (R) | ≤4 (S) | 2 (I) | ≥8 (R) | 0.25 (S) | ≤0.25 (S) | ≤4 (S) | ≤1 (S) | ≤1 (S) | ≥8 (R) | 2 (S) | ESBL positive |
| Etest | 24 (R) | 0.5 (S) | 4 (I) | >32 (R) | 0.008 (S) | 0.016 (S) | 2 (S) | 0.75 (S) | 0.75 (S) | >32 (R) | 1 (S) | ||
| E. coli (5) | ACC | ≥64 (R) | 128 (R) | ≤1 (S) | 0.5 (S) | 0.25 (S) | ≤0.25 (S) | ≤4 (S) | ≤1 (S) | ≤1 (S) | ≥8 (R) | ≤0.5 (S) | CAZ, CTX susceptible |
| Etest | >256 (R) | >256 (R) | 0.38 (S) | 0.125 (S) | 0.012 (S) | 0.032 (S) | 2 (S) | 0.5 (S) | 0.75 (S) | >32 (R) | 2 (S) | ||
| E. coli (6) | ACC | ≥64 (R) | ≤4 (S) | ≥32 (R) | ≥8 (R) | 0.25 (S) | ≤0.25 (S) | 16 (I) | 2 (S) | ≥32 (R) | ≥8 (R) | 2 (S) | ESBL positive |
| Etest | 64 (R) | 4 (S) | 12 (R) | >32 (R) | 0.012 (S) | 0.023 (S) | 8 (S) | 0.5 (S) | 16 (R) | >32 (R) | 1.5 (S) | ||
| E. coli (7) | ACC | ≥64 (R) | 128 (R) | ≤1 (S) | ≤0.25 (S) | ≤0.125 (S) | ≤0.25 (S) | ≤4 (S) | 16 (R) | 16 (R) | ≥8 (R) | ≤0.5 (S) | CAZ, CTX susceptible |
| Etest | >256 (R) | 64 (R) | 1 (S) | 0.094 (S) | 0.008 (S) | 0.016 (S) | 1 (S) | 12 (R) | 16 (R) | >32 (R) | 1 (S) | ||
| E. coli (8) | ACC | 16 (R) | ≤4 (S) | ≤1 (S) | ≥8 (R) | 0.25 (S) | ≤0.25 (S) | ≤4 (S) | 2 (S) | ≤1 (S) | ≥8 (R) | ≤0.5 (S) | ESBL positive |
| Etest | * | 0.38 (S) | * | >32 (R) | 0.006 (S) | 0.012 (S) | 1 (S) | 0.38 (S) | 0.75 (S) | >32 (R) | 0.75 (S) | ||
| E. coli (9) | ACC | 32 (R) | ≤4 (S) | 16 (R) | ≥8 (R) | 0.25 (S) | ≤0.25 (S) | ≤4 (S) | ≤1 (S) | ≤1 (S) | ≤0.25 (S) | ≤0.5 (S) | ESBL positive |
| Etest | 16 (R) | 0.5 (S) | 6 (R) | >32 (R) | 0.012 (S) | 0.016 (S) | 0.75 (S) | 0.25 (S) | 0.5 (S) | 0.094 (S) | 1 (S) | ||
| E. coli (10) | ACC | ≥64 (R) | ≤4 (S) | ≥32 (R) | ≥8 (R) | 0.25 (S) | ≤0.25 (S) | ≤4 (S) | 16 (R) | 8 (R) | ≥8 (R) | 2 (S) | ESBL positive |
| Etest | 64 (R) | 0.75 (S) | 16 (R) | >32 (R) | 0.023 (S) | 0.032 (S) | 1.5 (S) | 0.5 (S) | 1 (S) | >32 (R) | 1 (S) | ||
| P. aeruginosa (11) | ACC | – | 128 (R) | 32 (R) | – | – | ≥16 (R) | ≥128 (R) | ≥32 (R) | ≥32 (R) | ≥8 (R) | ≤0.5 (S) | MDR phenotype |
| Etest | ND | >256 (R) | 96 (R) | ND | ND | >32 (R) | 24 (R) | >256 (R) | >256 (R) | >32 (R) | 2 (S) | ||
| P. aeruginosa (12) | ACC | – | 128 (R) | 32 (R) | – | – | 4 (I) | ≤4 (S) | 16 (R) | 16 (R) | ≥8 (R) | ≤0.5 (S) | MDR phenotype |
| Etest | ND | >256 (R) | >256 (R) | ND | ND | >32 (R) | 16 (I) | >256 (R) | >256 (R) | >32 (R) | 1.5 (S) | ||
| P. aeruginosa (13) | ACC | – | 128 (R) | 32 (R) | – | – | ≥16 (R) | ≥128 (R) | 16 (R) | ≥32 (R) | ≥8 (R) | ≤0.5 (S) | MDR phenotype |
| Etest | ND | 12 (S) | 24 (R) | ND | ND | >32 (R) | 24 (R) | 16 (R) | 24 (R) | >32 (R) | 0.75 (S) | ||
In all, seven E. coli isolates were third-generation cephalosporin-resistant ESBL producers, and three P. aeruginosa isolates had a multidrug-resistant phenotype. The nonsusceptible phenotype was correctly detected by the Accelerate Pheno system for piperacillin-tazobactam, ceftriaxone, and meropenem in all 13 isolates (identified parenthetically as isolates 1 to 13 in column 1).
ACC, Accelerate Pheno.
Isolates are identified parenthetically as resistant (R), susceptible (S), or intermediate (I). *, Discrepant result between the Vitek 2 and the Etest were excluded from the evaluation study. –, The AST measurement was not performed by the Accelerate Pheno system for the antibiotic-pathogen combination. MDR, multidrug resistant; ND, not done; AMK, amikacin; CAZ, ceftazidime; CIP, ciprofloxacin; CRO, ceftriaxone; CST, colistin; CTX, cefotaxime; ETP, ertapenem; FEP, cefepime; GEN, gentamicin; MEM, meropenem; SAM, ampicillin-sulbactam; TOB, tobramycin; TZP, piperacillin-tazobactam.