Table 1.
Minimum inhibitory concentration (MIC) range, MIC50, MIC90, and percentage of susceptibility of 148 animal Francisella tularensis subsp. holarctica field isolates to 22 antimicrobial agents.
| Antimicrobial Agent (Concentrations Used in mg/L) | MIC Range (mg/L) | MIC50 (mg/L) | MIC90 (mg/L) | Breakpoint (mg/L) * | Susceptibility of Isolates to Antimicrobial Agents (%) |
|---|---|---|---|---|---|
| Ampicillin (4–32) | <4 to >32 | >32 | >32 | ≤4 a | 2.0 |
| Ampicillin/sulbactam (4–32/2–16) | <4/2 to >32/16 | >32/16 | >32/16 | ≤4 a | 1.4 |
| Piperacillin/tazobactam (16/4–128/4) | <16/4 to >128/4 | <16/4 | 32/4 | ≤8 b | 0.0 |
| Ticarcillin/clavulanic acid (16/2–64/2) | <16/2 to >64/2 | 16/2 | >64/2 | ≤16 c | 15.5 |
| Ertapenem (2–16) | <2 to >16 | >16 | >16 | ≤4 d | 23.7 |
| Meropenem (1–8) | <1 to >8 | >8 | >8 | ≤4 a | 6.1 |
| Aztreonam (4–32) | <4 to >32 | >32 | >32 | ≤8 b | 7.4 |
| Cephalothin (2–16) | <2 to >16 | >16 | >16 | ≤8 e | 3.4 |
| Cefazolin (4–32) | <4 to >32 | >32 | >32 | ≤8 e | 5.4 |
| Cefoxitin (4–32) | <4 to >32 | 32 | >32 | --- | --- |
| Ceftazidime (1–32) | <1 to 32 | 1 | 4 | ≤1 b | 38.5 |
| Ceftriaxone (1–64) | <1 to >64 | 2 | 8 | ≤1 b | 8.1 |
| Cefuroxime (4–32) | <4 to >32 | >32 | >32 | ≤8 b | 2.7 |
| Cefepime (4–32) | <4 to >32 | 32 | >32 | ≤4 b | 3.4 |
| Cefpodoxime (2–16) | <2 to >16 | 4 | >16 | ≤2 c | 8.1 |
| Amikacin (8–64) | <8 to 32 | <8 | <8 | ≤16 e | 98.0 |
| Gentamicin (2–16) | <2 to 16 | <2 | <2 | ≤8 f | 98.7 |
| Tobramycin (4–8) | <4 to 8 | <4 | <4 | ≤8 g | 96.6 |
| Tetracycline (0.5–16) | <0.5 to >16 | 2 | 2 | ≤4 f | 94.6 |
| Tigecycline (1–8) | <1 to 8 | <1 | 2 | ≤2 h | 76.4 |
| Ciprofloxacin (0.5–4) | <0.5 to >4 | <0.5 | <0.5 | ≤0.5 f | 92.6 |
| Sulfamethoxazole/trimethoprim (9.5/0.5–76/4) |
<9.5/<0.5 to >76/>4 | >76/>4 | >76/>4 | ≤38/2 c | 23.0 |
* Breakpoint: Concentration (in mg/L) of antimicrobial agent that defines whether a given bacterium (F. tularensis subsp. holarctica in this case) is susceptible or resistant to the compound; a [9]; b [10] (for Enterobacteriaceae); c [11,12] (for Enterobacteriaceae); d [11,12] (for meropenem); e [11,12]; f [13]; g [13] (for gentamicin); h [14].