TABLE 3.
MIC50, MIC90, range, percentage of resistant and nonsusceptible E. coli strains (n = 119) producing enzymes, from the CTX-M-1 and CTX-M-9 groups, collected in nine Portuguese hospitals
| Antimicrobial agent | MIC (μg/ml) for strains producing:
|
CLSI breakpointsb (μg/ml)
|
||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| CTX-M group 1a (n = 110)
|
CTX-M group 9 (n = 9)
|
|||||||||||
| MIC50c | MIC90d | Range | Susceptibilitye
|
MIC50 | MIC90 | Range | Susceptibility
|
S | R | |||
| R (%) | IR (%) | R (%) | IR (%) | |||||||||
| Ampicillin | >16 | >16 | 4->16 | 110 (100) | 110 (100) | >16 | >16 | 4->16 | 9 (100) | 9 (100) | ≤8 | ≥32 |
| Ampicillin-sulbactam | >16/8 | >16/8 | 8/4->16/8 | 108 (98) | 109 (99) | >16/8 | >16/8 | 8/4->16/8 | 9 (100) | 9 (100) | ≤8/4 | ≥32/16 |
| Amoxicillin-clavulanic acid | 8/4 | 16/8 | 4/2-16/8 | 3 (3) | 28 (26) | ≤4/2 | 8/4 | ≤4/2-16/8 | 0 (0) | 0 (0) | ≤8/4 | ≥32/16 |
| Piperacillin | >64 | >64 | 16->64 | 110 (100) | 110 (100) | >64 | >64 | 16->64 | 9 (100) | 9 (100) | ≤16 | ≥128 |
| Piperacillin-tazobactam | ≤16 | 32 | ≤16-64 | 7 (6) | 13 (12) | ≤16 | ≤16 | ≤16-64 | 0 (0) | 0 (0) | ≤16/4 | ≥128/4 |
| Ticarcillin | >64 | >64 | 8->64 | 110 (100) | 110 (100) | >64 | >64 | 8->64 | 9 (100) | 9 (100) | ≤16 | ≥128 |
| Cephalothin | >16 | >16 | 8->16 | 110 (100) | 110 (100) | >16 | >16 | 8->16 | 9 (100) | 9 (100) | ≤8 | ≥32 |
| Cefazolin | >16 | >16 | 1->16 | 110 (100) | 110 (100) | >16 | >16 | 1->16 | 9 (100) | 9 (100) | ≤8 | ≥32 |
| Cefuroxime | >16 | >16 | 2->16 | 110 (100) | 110 (100) | >16 | >16 | 2->16 | 9 (100) | 9 (100) | ≤8 | ≥32 |
| Cefotaxime | >32 | >32 | 0.5->32 | 109 (99) | 110 (100) | >32 | >32 | 0.5->32 | 9 (100) | 9 (100) | ≤8 | ≥64 |
| Ceftriaxone | >32 | >32 | 2->32 | 110 (100) | 110 (100) | >32 | >32 | 2->32 | 9 (100) | 9 (100) | ≤8 | ≥64 |
| Aztreonam | >16 | >16 | 1->16 | 110 (100) | 110 (100) | 8 | >16 | 1->16 | 1 (11) | 2 (22) | ≤8 | ≥32 |
| Ceftazidime | >16 | >16 | 0.5->16 | 108 (98) | 109 (99) | 2 | >16 | 0.5->16 | 1 (11) | 1 (11) | ≤8 | ≥32 |
| Cefepime | >16 | >16 | 0.5->16 | 109 (99) | 109 (99) | >16 | >16 | 0.5->16 | 7 (78) | 9 (100) | ≤8 | ≥32 |
| Cefoxitin | ≤4 | 8 | ≤4-16 | 1 (1) | 5 (5) | ≤4 | 16 | ≤4-16 | 0 (0) | 1 (11) | ≤8 | ≥32 |
| Imipenem | ≤0.5 | ≤0.5 | ≤0.5-8 | 0 (0) | 0 (0) | ≤0.5 | ≤0.5 | ≤0.5-8 | 0 (0) | 0 (0) | ≤4 | ≥16 |
| Meropenem | ≤1 | ≤1 | ≤1-8 | 0 (0) | 0 (0) | ≤1 | ≤1 | ≤1-8 | 0 (0) | 0 (0) | ≤4 | ≥16 |
| Amikacin | ≤8 | 16 | ≤8-32 | 4 (4) | 8 (7) | ≤8 | 16 | ≤8-32 | 0 (0) | 0 (0) | ≤16 | ≥64 |
| Gentamicin | >8 | >8 | 2->8 | 87 (79) | 87 (79) | ≤2 | >8 | ≤2->8 | 2 (22) | 2 (22) | ≤4 | ≥16 |
| Tobramycin | >8 | >8 | 2->8 | 103 (94) | 104 (95) | ≤2 | >8 | ≤2->8 | 2 (22) | 2 (22) | ≤4 | ≥16 |
| Ciprofloxacin | >2 | >2 | 0.5->2 | 108 (98) | 108 (98) | ≤0.5 | >2 | ≤0.5->2 | 3 (33) | 3 (33) | ≤1 | ≥4 |
| Norfloxacin | >8 | >8 | 2->8 | 108 (98) | 108 (98) | ≤2 | >8 | ≤2->8 | 3 (33) | 3 (33) | ≤4 | ≥16 |
| Ofloxacin | >4 | >4 | 0.5->4 | 108 (98) | 108 (98) | ≤0.5 | >4 | ≤0.5->4 | 3 (33) | 3 (33) | ≤2 | ≥8 |
| Trimethoprim-sulfamethoxazole | ≤1/19 | >2/38 | ≤1/19->2/38 | 28 (26) | 28 (26) | ≤1/19 | >2/38 | ≤1/19->2/38 | 3 (33) | 3 (33) | ≤2/38 | ≥4/76 |
a
There were a total of 99 CTX-M-15 producers and 1 CTX-M-32 producer, according to the phylogenetic group 1 defined by Bonnet (3).
b
As scored according to CLSI guidelines: S, sensitive; R, resistant.
c
MIC50, MIC at which 50% of the isolates are inhibited.
d
MIC90, MIC at which 90% of the isolates tested are inhibited.
e
R, number of resistant isolates; IR, number of nonsusceptible isolates.