TABLE 1.
Patient no. | P. aeruginosa isolatea | Activity of treatment antibioticsb |
Combination bactericidal activity (MCBT)c |
Result of combination synergy testing |
|||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Antibiotic 1 in the combination |
Antibiotic 2 in the combination |
||||||||||
Agent | MIC (mg/liter) | MBC (mg/liter) | Agent | MIC (mg/liter) | MBC (mg/liter) | High | Low | Checkerboard result | TK curve analysis result at 24 h | ||
1 | 1 | ATM | 128 | >256 | TOB | 8 | 16 | Yes | No | Synergy | Indifference |
2 | 1a | ATM | 32 | 64 | TOB | 8 | 16 | Yes | Yes | Indifference | Indifference |
1b | ATM | 64 | 128 | TOB | 16 | 16 | No | No | Synergy | Synergy | |
3 | 1 | CAZ | 16 | 64 | TOB | 8 | 32 | No | No | Synergy | Indifference |
2 | CAZ | 16 | 64 | TOB | 8 | 32 | Yes | No | Synergy | Indifference | |
3 | CAZ | 16 | 64 | TOB | 8 | 16 | No | No | Synergy | Indifference | |
4 | 1a | CAZ | 32 | 32 | TOB | 8 | 8 | Yes | Yes | Indifference | Indifference |
1b | CAZ | 8 | 32 | TOB | 4 | 4 | Yes | Yes | Synergy | Indifference | |
1c | CAZ | 8 | 8 | TOB | 4 | 8 | Yes | Yes | Synergy | Indifference | |
5 | 1 | MEM | 8 | 16 | TOB | 4 | 4 | Yes | No | Indifference | Indifference |
6 | 1a | MEM | 8 | 16 | TOB | 16 | 16 | Yes | No | Synergy | Indifference |
1b | MEM | 8 | 16 | TOB | 32 | 32 | Yes | No | Indifference | Indifference | |
2 | MEM | 8 | 16 | TOB | 8 | 16 | Yes | No | Indifference | Indifference | |
3a | MEM | 32 | 32 | TOB | 32 | 32 | Yes | No | Indifference | Synergy | |
3b | MEM | 16 | 32 | TOB | 32 | 32 | Yes | No | Synergy | Synergy | |
7 | 1 | TZP | 256 | 128 | TOB | 32 | 32 | No | No | Indifference | Indifference |
2 | TZP | >256 | 64 | TOB | 8 | 16 | No | No | Indifference | Indifference | |
8 | 1 | CAZ | 128 | >256 | TZP | >256 | >256 | No | No | Indifference | Not tested |
9 | 1 | CAZ | 32 | >128 | TOB | 4 | 8 | Yes | No | Indifference | Indifference |
2a | CAZ | 32 | >128 | TOB | 4 | 8 | Yes | Yes | Indifference | Indifference | |
2b | CAZ | 32 | >128 | TOB | 8 | 16 | No | No | Indifference | Indifference | |
3 | CAZ | 32 | >128 | TOB | 8 | 16 | No | No | Synergy | Indifference |
The number refers to the morphotype, and the letter (a, b, or c) refers to the different isolates of that morphotype.
ATM, aztreonam; CAZ, ceftazidime; MEM, meropenem; TOB, tobramycin; TZP, piperacillin-tazobactam.
The result of combination bactericidal activity are yes, killed by the combination or a high concentration of a single antibiotic, and no, not killed. The concentrations used for the high-concentration MCBT were 32 mg/liter for aztreonam, 32 mg/liter for ceftazidime, 32 mg/liter for meropenem, 4 mg/liter for tobramycin, and 32/4 mg/liter for piperacillin-tazobactam; and those used for the low-concentration MCBT were 8 mg/liter for aztreonam, 8 mg/liter for ceftazidime, 4 mg/liter for meropenem, 4 mg/liter for tobramycin, and 16/2 mg/liter for piperacillin-tazobactam.