TABLE 2.

Summary of results for each patient, giving the size of the resistant subpopulation and a comparison of results of antibiotic combination testing with the clinical and bacterial response to antibiotics^a

Patient no.	Antibiotics used for treatmentb	P. aeruginosa count (CFU/g) at day 0		MCBTc		Checkerboard result	TK curve analysis result	Response to treatmentd
		Total	Resistant	High	Low			FEV1	CFU/g sputum
1	TOB + ATM	6.3 × 107	1.1 × 107	Yes	No	Synergy	Indifference	Not valide	Not valid
2	TOB + ATM	2.2 × 108	4.4 × 107	No	No	Indifference	Indifference	Yes	No change
3	TOB + CAZ	1.0 × 108	2.3 × 107	No	No	Synergy	Indifference	No	No change
4	TOB + CAZ	7.1 × 108	1.9 × 108	Yes	Yes	Indifference	Indifference	Yes	No change
5	TOB + MEM	4.0 × 108	1.0 × 108	Yes	No	Indifference	Indifference	Yes	No change
6	TOB + MEM	4.2 × 107	4.1 × 107	Yes	No	Indifference	Indifference	Not donef	No change
7	TOB + TZP	1.8 × 108	7.0 × 107	No	No	Indifference	Indifference	Not valid	Not valid
8g	CAZ + TZP	2.0 × 108	1.7 × 107	No	No	Indifference	Not tested	No	No change
9	TOB + CAZ	3.0 × 108	6.0 × 106	No	No	Indifference	Indifference	Yes	No change

^aFor the results the most resistant isolate (i.e., the organism least affected by the antibiotic combinations) is quoted.

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

^cThe results 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.

^dThe response is that after 14 days of antibiotic treatment. See Materials and Methods for the full definition of the clinical and microbiological responses to treatment after 14 days of antibiotic treatment.

^eThe antibiotic treatment was changed at day 7 because of a poor response to the initial treatment regimen.

^fThis patient developed a pneumothorax, and lung function could not be measured at day 14.

^gThe total CFU for patient 8 was a combination of P. aeruginosa and an antibiotic-susceptible strain of Achromobacter xylosoxidans. The resistant subpopulation was just P. aeruginosa.