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. 2009 Aug 24;53(11):4809–4815. doi: 10.1128/AAC.00269-09

TABLE 1.

Activities of single antibiotics (MICs and MBCs) and antibiotic combinations (MCBT, checkerboard, or TK curve methodology) against isolates of P. aeruginosa

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
a

The number refers to the morphotype, and the letter (a, b, or c) refers to the different isolates of that morphotype.

b

ATM, aztreonam; CAZ, ceftazidime; MEM, meropenem; TOB, tobramycin; TZP, piperacillin-tazobactam.

c

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.