Table 2.
Antimicrobial susceptibility of Acinetobacter baumannii strain A424 and its TnAbaR23-minus mutants
| Strain | Zone of inhibition diam (MIC) of strain to the following antibiotica: |
|||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| TET (10 μg) | IMPc (10 μg) | CAR (100 μg) | AMP (25 μg) | TIM (75 μg) | CTX (30 μg) | CIPc (5 μg) | STR (10 μg) | TOB (10 μg) | AMK (30 μg) | GENc (10 μg) | TMP (2.5 μg) | SUL (25 μg) | SXT (25 μg) | CHL (10 μg) | RIF (2 μg) | |
| AYEb | 6.0 | 28.0 (0.38) | 6.0 | 6.0 | 6.0 | 6.0 (>256) | 6.5 (>32) | 9.0 | 13.0 | 17.0 | 8.5 (16) | 6.0 | 6.0 (>1,024) | 6.0 | 6.0 | 6.0 |
| A424 | 6.0 | 15.0(4) | 6.0 | 6.0 | 6.0 | 6.0 (>256) | 14.0 (4) | 16.0 | 26.0 | 16.0 (12) | 23.0 (0.75) | 6.5 | 6.0 (>1,024) | 6.0 | 6.0 | 11.5 |
| DCO163 | 15.0 | 18.0(2) | 6.0 | 6.0 | 6.0 | 6.0 (>256) | 16.0 (3) | 11.0 | 23.0 | 11.0 (48) | 9.0 (16) | 10.0 | 31.0 (0.75) | 30.5 | 6.0 | 11.5 |
| DCO174 | 9.5 | 15.0(4) | 6.0 | 6.0 | 6.0 | 6.0 (>256) | 6.0 (>32) | 9.0 | 23.0 | 9.0 (96) | 6.0 (48) | 6.0 | 23.5 (4) | 21.5 | 6.0 | 13.0 |
| NCTC12241b | 20.0 | 35.0 | 18.0 | 13.0 | NA | 35.0 | 30.0 | 17.0 | 21.0 | 24.0 (1.5) | 23.0 | 26.0 | 6.0 (>1,024) | 29.0 | 20.0 | 6.0 |
Antibiotic abbreviations: TET, tetracycline; IMP, imipenem; CAR, carbenicillin; AMP, ampicillin; TIM, ticarcillin-clavulanate; CTX, cefotaxime; CIP, ciprofloxacin; STR, streptomycin; TOB, tobramycin; AMK, amikacin; GEN, gentamicin; TMP, trimethoprim; SUL, sulfamethoxazole; SXT, sulfamethoxazole-trimethoprim; CHL, chloramphenicol; RIF, rifampin. The mass of antibiotic is given in parentheses after the antibiotic. NA, not available.
AYE data were in accordance with previously published resistance data (Adams et al. [2] and references cited therein). E. coli strain NCTC12241 was used as a BSAC reference control.
BSAC guidelines (3) on zone diameter breakpoints were as follows: for IMP, resistant (R) ≤ 13 mm, susceptible (S) ≥ 25 mm, and intermediate (I) = 14 to 24 mm; for CIP, R ≤ 20 mm and S ≥ 21 mm. BSAC (3) guidelines on MIC breakpoints for Acinetobacter species: for GEN, R > 4 mg/liter and S ≤ 4 mg/liter; for CIP, R > 1 mg/liter and S ≤ 1 mg/liter; for IMP, R > 8 mg/liter, S ≤ 2 mg/liter, and I = 4 to 8 mg/liter. Numbers shown in boldface type and underlined indicate resistant and intermediate, respectively, by BSAC interpretive criteria. MIC was tested using Etest strips (AB bioMérieux, Sweden), and the MIC results for antibiotics tested are shown in parentheses in the table. Each assay was repeated at least three times. Zone diameters are shown to the nearest 0.5 mm, while MIC is shown in milligrams per liter.